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<?xml version="1.0" encoding="iso-8859-1"?>
<!--
The FreeBSD Documentation Project
$FreeBSD: head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml 50922 2017-09-25 19:33:51Z bcr $
-->
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
xml:id="network-servers">
<!--
<chapterinfo>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Reorganized by in July 2004</contrib>
</author>
</authorgroup>
</chapterinfo>
-->
<title>Network Servers</title>
<sect1 xml:id="network-servers-synopsis">
<title>Synopsis</title>
<para>This chapter covers some of the more frequently used network
services on &unix; systems. This includes installing,
configuring, testing, and maintaining many different types of
network services. Example configuration files are included
throughout this chapter for reference.</para>
<para>By the end of this chapter, readers will know:</para>
<itemizedlist>
<listitem>
<para>How to manage the <application>inetd</application>
daemon.</para>
</listitem>
<listitem>
<para>How to set up the Network File System
(<acronym>NFS</acronym>).</para>
</listitem>
<listitem>
<para>How to set up the Network Information Server
(<acronym>NIS</acronym>) for centralizing and sharing
user accounts.</para>
</listitem>
<listitem>
<para>How to set &os; up to act as an <acronym>LDAP</acronym>
server or client</para>
</listitem>
<listitem>
<para>How to set up automatic network settings using
<acronym>DHCP</acronym>.</para>
</listitem>
<listitem>
<para>How to set up a Domain Name Server
(<acronym>DNS</acronym>).</para>
</listitem>
<listitem>
<para>How to set up the <application>Apache</application>
<acronym>HTTP</acronym> Server.</para>
</listitem>
<listitem>
<para>How to set up a File Transfer Protocol
(<acronym>FTP</acronym>) server.</para>
</listitem>
<listitem>
<para>How to set up a file and print server for &windows;
clients using <application>Samba</application>.</para>
</listitem>
<listitem>
<para>How to synchronize the time and date, and set up a
time server using the Network Time Protocol
(<acronym>NTP</acronym>).</para>
</listitem>
<listitem>
<para>How to set up <acronym>iSCSI</acronym>.</para>
</listitem>
</itemizedlist>
<para>This chapter assumes a basic knowledge of:</para>
<itemizedlist>
<listitem>
<para><filename>/etc/rc</filename> scripts.</para>
</listitem>
<listitem>
<para>Network terminology.</para>
</listitem>
<listitem>
<para>Installation of additional third-party
software (<xref linkend="ports"/>).</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 xml:id="network-inetd">
<title>The <application>inetd</application>
Super-Server</title>
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Chern</firstname>
<surname>Lee</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<contrib>Updated by </contrib>
<othername>The &os; Documentation Project</othername>
</author>
</authorgroup>
</sect1info>
-->
<para>The &man.inetd.8; daemon is sometimes referred to as a
Super-Server because it manages connections for many services.
Instead of starting multiple applications, only the
<application>inetd</application> service needs to be started.
When a connection is received for a service that is managed by
<application>inetd</application>, it determines which program
the connection is destined for, spawns a process for that
program, and delegates the program a socket. Using
<application>inetd</application> for services that are not
heavily used can reduce system load, when compared to running
each daemon individually in stand-alone mode.</para>
<para>Primarily, <application>inetd</application> is used to
spawn other daemons, but several trivial protocols are handled
internally, such as <application>chargen</application>,
<application>auth</application>,
<application>time</application>,
<application>echo</application>,
<application>discard</application>, and
<application>daytime</application>.</para>
<para>This section covers the basics of configuring
<application>inetd</application>.</para>
<sect2 xml:id="network-inetd-conf">
<title>Configuration File</title>
<para>Configuration of <application>inetd</application> is
done by editing <filename>/etc/inetd.conf</filename>. Each
line of this configuration file represents an application
which can be started by <application>inetd</application>. By
default, every line starts with a comment
(<literal>#</literal>), meaning that
<application>inetd</application> is not listening for any
applications. To configure <application>inetd</application>
to listen for an application's connections, remove the
<literal>#</literal> at the beginning of the line for that
application.</para>
<para>After saving your edits, configure
<application>inetd</application> to start at system boot by
editing <filename>/etc/rc.conf</filename>:</para>
<programlisting>inetd_enable="YES"</programlisting>
<para>To start <application>inetd</application> now, so that it
listens for the service you configured, type:</para>
<screen>&prompt.root; <userinput>service inetd start</userinput></screen>
<para>Once <application>inetd</application> is started, it needs
to be notified whenever a modification is made to
<filename>/etc/inetd.conf</filename>:</para>
<example xml:id="network-inetd-reread">
<title>Reloading the <application>inetd</application>
Configuration File</title>
<screen>&prompt.root; <userinput>service inetd reload</userinput></screen>
</example>
<para>Typically, the default entry for an application does not
need to be edited beyond removing the <literal>#</literal>.
In some situations, it may be appropriate to edit the default
entry.</para>
<para>As an example, this is the default entry for &man.ftpd.8;
over IPv4:</para>
<programlisting>ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l</programlisting>
<para>The seven columns in an entry are as follows:</para>
<programlisting>service-name
socket-type
protocol
{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]
user[:group][/login-class]
server-program
server-program-arguments</programlisting>
<para>where:</para>
<variablelist>
<varlistentry>
<term>service-name</term>
<listitem>
<para>The service name of the daemon to start. It must
correspond to a service listed in
<filename>/etc/services</filename>. This determines
which port <application>inetd</application> listens on
for incoming connections to that service. When using a
custom service, it must first be added to
<filename>/etc/services</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>socket-type</term>
<listitem>
<para>Either <literal>stream</literal>,
<literal>dgram</literal>, <literal>raw</literal>, or
<literal>seqpacket</literal>. Use
<literal>stream</literal> for TCP connections and
<literal>dgram</literal> for
<acronym>UDP</acronym> services.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>protocol</term>
<listitem>
<para>Use one of the following protocol names:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>Protocol Name</entry>
<entry>Explanation</entry>
</row>
</thead>
<tbody>
<row>
<entry>tcp or tcp4</entry>
<entry>TCP IPv4</entry>
</row>
<row>
<entry>udp or udp4</entry>
<entry><acronym>UDP</acronym> IPv4</entry>
</row>
<row>
<entry>tcp6</entry>
<entry>TCP IPv6</entry>
</row>
<row>
<entry>udp6</entry>
<entry><acronym>UDP</acronym> IPv6</entry>
</row>
<row>
<entry>tcp46</entry>
<entry>Both TCP IPv4 and IPv6</entry>
</row>
<row>
<entry>udp46</entry>
<entry>Both <acronym>UDP</acronym> IPv4 and
IPv6</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</listitem>
</varlistentry>
<varlistentry>
<term>{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]</term>
<listitem>
<para>In this field, <option>wait</option> or
<option>nowait</option> must be specified.
<option>max-child</option>,
<option>max-connections-per-ip-per-minute</option> and
<option>max-child-per-ip</option> are optional.</para>
<para><option>wait|nowait</option> indicates whether or
not the service is able to handle its own socket.
<option>dgram</option> socket types must use
<option>wait</option> while
<option>stream</option> daemons, which are usually
multi-threaded, should use <option>nowait</option>.
<option>wait</option> usually hands off multiple sockets
to a single daemon, while <option>nowait</option> spawns
a child daemon for each new socket.</para>
<para>The maximum number of child daemons
<application>inetd</application> may spawn is set by
<option>max-child</option>. For example, to limit ten
instances of the daemon, place a <literal>/10</literal>
after <option>nowait</option>. Specifying
<literal>/0</literal> allows an unlimited number of
children.</para>
<para><option>max-connections-per-ip-per-minute</option>
limits the number of connections from any particular
<acronym>IP</acronym> address per minute. Once the
limit is reached, further connections from this IP
address will be dropped until the end of the minute.
For example, a value of <literal>/10</literal> would
limit any particular <acronym>IP</acronym> address to
ten connection attempts per minute.
<option>max-child-per-ip</option> limits the number of
child processes that can be started on behalf on any
single <acronym>IP</acronym> address at any moment.
These options can limit excessive resource consumption
and help to prevent Denial of Service attacks.</para>
<para>An example can be seen in the default settings for
&man.fingerd.8;:</para>
<programlisting>finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -k -s</programlisting>
</listitem>
</varlistentry>
<varlistentry>
<term>user</term>
<listitem>
<para>The username the daemon
will run as. Daemons typically run as
<systemitem class="username">root</systemitem>,
<systemitem class="username">daemon</systemitem>, or
<systemitem class="username">nobody</systemitem>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>server-program</term>
<listitem>
<para>The full path to the daemon. If the daemon is a
service provided by <application>inetd</application>
internally, use <option>internal</option>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>server-program-arguments</term>
<listitem>
<para>Used to specify any command arguments to be passed
to the daemon on invocation. If the daemon is an
internal service, use
<option>internal</option>.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 xml:id="network-inetd-cmdline">
<title>Command-Line Options</title>
<para>Like most server daemons, <application>inetd</application>
has a number of options that can be used to modify its
behavior. By default, <application>inetd</application> is
started with <literal>-wW -C 60</literal>. These options
enable TCP wrappers for all services, including internal
services, and prevent any <acronym>IP</acronym> address from
requesting any service more than 60 times per minute.</para>
<para>To change the default options which are passed to
<application>inetd</application>, add an entry for
<literal>inetd_flags</literal> in
<filename>/etc/rc.conf</filename>. If
<application>inetd</application> is already running, restart
it with <command>service inetd restart</command>.</para>
<para>The available rate limiting options are:</para>
<variablelist>
<varlistentry>
<term>-c maximum</term>
<listitem>
<para>Specify the default maximum number of simultaneous
invocations of each service, where the default is
unlimited. May be overridden on a per-service basis by
using <option>max-child</option> in
<filename>/etc/inetd.conf</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-C rate</term>
<listitem>
<para>Specify the default maximum number of times a
service can be invoked from a single
<acronym>IP</acronym> address per minute. May be
overridden on a per-service basis by using
<option>max-connections-per-ip-per-minute</option> in
<filename>/etc/inetd.conf</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-R rate</term>
<listitem>
<para>Specify the maximum number of times a service can be
invoked in one minute, where the default is
<literal>256</literal>. A rate of <literal>0</literal>
allows an unlimited number.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-s maximum</term>
<listitem>
<para>Specify the maximum number of times a service can be
invoked from a single <acronym>IP</acronym> address at
any one time, where the default is unlimited. May be
overridden on a per-service basis by using
<option>max-child-per-ip</option> in
<filename>/etc/inetd.conf</filename>.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Additional options are available. Refer to &man.inetd.8;
for the full list of options.</para>
</sect2>
<sect2 xml:id="network-inetd-security">
<title>Security Considerations</title>
<para>Many of the daemons which can be managed by
<application>inetd</application> are not security-conscious.
Some daemons, such as <application>fingerd</application>, can
provide information that may be useful to an attacker. Only
enable the services which are needed and monitor the system
for excessive connection attempts.
<literal>max-connections-per-ip-per-minute</literal>,
<literal>max-child</literal> and
<literal>max-child-per-ip</literal> can be used to limit such
attacks.</para>
<para>By default, TCP wrappers is enabled. Consult
&man.hosts.access.5; for more information on placing TCP
restrictions on various
<application>inetd</application> invoked daemons.</para>
</sect2>
</sect1>
<sect1 xml:id="network-nfs">
<info>
<title>Network File System (NFS)</title>
<authorgroup>
<author>
<personname>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
</personname>
<contrib>Reorganized and enhanced by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<personname>
<firstname>Bill</firstname>
<surname>Swingle</surname>
</personname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</info>
<indexterm><primary>NFS</primary></indexterm>
<para>&os; supports the Network File System
(<acronym>NFS</acronym>), which allows a server to share
directories and files with clients over a network. With
<acronym>NFS</acronym>, users and programs can access files on
remote systems as if they were stored locally.</para>
<para><acronym>NFS</acronym> has many practical uses. Some of
the more common uses include:</para>
<itemizedlist>
<listitem>
<para>Data that would otherwise be duplicated on each client
can be kept in a single location and accessed by clients
on the network.</para>
</listitem>
<listitem>
<para>Several clients may need access to the
<filename>/usr/ports/distfiles</filename> directory.
Sharing that directory allows for quick access to the
source files without having to download them to each
client.</para>
</listitem>
<listitem>
<para>On large networks, it is often more convenient to
configure a central <acronym>NFS</acronym> server on which
all user home directories are stored. Users can log into
a client anywhere on the network and have access to their
home directories.</para>
</listitem>
<listitem>
<para>Administration of <acronym>NFS</acronym> exports is
simplified. For example, there is only one file system
where security or backup policies must be set.</para>
</listitem>
<listitem>
<para>Removable media storage devices can be used by other
machines on the network. This reduces the number of devices
throughout the network and provides a centralized location
to manage their security. It is often more convenient to
install software on multiple machines from a centralized
installation media.</para>
</listitem>
</itemizedlist>
<para><acronym>NFS</acronym> consists of a server and one or more
clients. The client remotely accesses the data that is stored
on the server machine. In order for this to function properly,
a few processes have to be configured and running.</para>
<para>These daemons must be running on the server:</para>
<indexterm>
<primary>NFS</primary>
<secondary>server</secondary>
</indexterm>
<indexterm>
<primary>file server</primary>
<secondary>UNIX clients</secondary>
</indexterm>
<indexterm>
<primary><application>rpcbind</application></primary>
</indexterm>
<indexterm>
<primary><application>mountd</application></primary>
</indexterm>
<indexterm>
<primary><application>nfsd</application></primary>
</indexterm>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Daemon</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><application>nfsd</application></entry>
<entry>The <acronym>NFS</acronym> daemon which services
requests from <acronym>NFS</acronym> clients.</entry>
</row>
<row>
<entry><application>mountd</application></entry>
<entry>The <acronym>NFS</acronym> mount daemon which
carries out requests received from
<application>nfsd</application>.</entry>
</row>
<row>
<entry><application>rpcbind</application></entry>
<entry> This daemon allows <acronym>NFS</acronym>
clients to discover which port the
<acronym>NFS</acronym> server is using.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>Running &man.nfsiod.8; on the client can improve
performance, but is not required.</para>
<sect2 xml:id="network-configuring-nfs">
<title>Configuring the Server</title>
<indexterm>
<primary>NFS</primary>
<secondary>configuration</secondary>
</indexterm>
<para>The file systems which the <acronym>NFS</acronym> server
will share are specified in <filename>/etc/exports</filename>.
Each line in this file specifies a file system to be exported,
which clients have access to that file system, and any access
options. When adding entries to this file, each exported file
system, its properties, and allowed hosts must occur on a
single line. If no clients are listed in the entry, then any
client on the network can mount that file system.</para>
<indexterm>
<primary>NFS</primary>
<secondary>export examples</secondary>
</indexterm>
<para>The following <filename>/etc/exports</filename> entries
demonstrate how to export file systems. The examples can be
modified to match the file systems and client names on the
reader's network. There are many options that can be used in
this file, but only a few will be mentioned here. See
&man.exports.5; for the full list of options.</para>
<para>This example shows how to export
<filename>/cdrom</filename> to three hosts named
<replaceable>alpha</replaceable>,
<replaceable>bravo</replaceable>, and
<replaceable>charlie</replaceable>:</para>
<programlisting>/cdrom -ro <replaceable>alpha</replaceable> <replaceable>bravo</replaceable> <replaceable>charlie</replaceable></programlisting>
<para>The <literal>-ro</literal> flag makes the file system
read-only, preventing clients from making any changes to the
exported file system. This example assumes that the host
names are either in <acronym>DNS</acronym> or in
<filename>/etc/hosts</filename>. Refer to &man.hosts.5; if
the network does not have a <acronym>DNS</acronym>
server.</para>
<para>The next example exports <filename>/home</filename> to
three clients by <acronym>IP</acronym> address. This can be
useful for networks without <acronym>DNS</acronym> or
<filename>/etc/hosts</filename> entries. The
<literal>-alldirs</literal> flag allows subdirectories to be
mount points. In other words, it will not automatically mount
the subdirectories, but will permit the client to mount the
directories that are required as needed.</para>
<programlisting>/usr/home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4</programlisting>
<para>This next example exports <filename>/a</filename> so that
two clients from different domains may access that file
system. The <option>-maproot=root</option> allows <systemitem
class="username">root</systemitem> on the remote system to
write data on the exported file system as <systemitem
class="username">root</systemitem>. If
<literal>-maproot=root</literal> is not specified, the
client's <systemitem class="username">root</systemitem> user
will be mapped to the server's <systemitem
class="username">nobody</systemitem> account and will be
subject to the access limitations defined for <systemitem
class="username">nobody</systemitem>.</para>
<programlisting>/a -maproot=root host.example.com box.example.org</programlisting>
<para>A client can only be specified once per file system. For
example, if <filename>/usr</filename> is a single file system,
these entries would be invalid as both entries specify the
same host:</para>
<programlisting># Invalid when /usr is one file system
/usr/src client
/usr/ports client</programlisting>
<para>The correct format for this situation is to use one
entry:</para>
<programlisting>/usr/src /usr/ports client</programlisting>
<para>The following is an example of a valid export list, where
<filename>/usr</filename> and <filename>/exports</filename>
are local file systems:</para>
<programlisting># Export src and ports to client01 and client02, but only
# client01 has root privileges on it
/usr/src /usr/ports -maproot=root client01
/usr/src /usr/ports client02
# The client machines have root and can mount anywhere
# on /exports. Anyone in the world can mount /exports/obj read-only
/exports -alldirs -maproot=root client01 client02
/exports/obj -ro</programlisting>
<para>To enable the processes required by the
<acronym>NFS</acronym> server at boot time, add these options
to <filename>/etc/rc.conf</filename>:</para>
<programlisting>rpcbind_enable="YES"
nfs_server_enable="YES"
mountd_flags="-r"</programlisting>
<para>The server can be started now by running this
command:</para>
<screen>&prompt.root; <userinput>service nfsd start</userinput></screen>
<para>Whenever the <acronym>NFS</acronym> server is started,
<application>mountd</application> also starts automatically.
However, <application>mountd</application> only reads
<filename>/etc/exports</filename> when it is started. To make
subsequent <filename>/etc/exports</filename> edits take effect
immediately, force <application>mountd</application> to reread
it:</para>
<screen>&prompt.root; <userinput>service mountd reload</userinput></screen>
</sect2>
<sect2>
<title>Configuring the Client</title>
<para>To enable <acronym>NFS</acronym> clients, set this option
in each client's <filename>/etc/rc.conf</filename>:</para>
<programlisting>nfs_client_enable="YES"</programlisting>
<para>Then, run this command on each <acronym>NFS</acronym>
client:</para>
<screen>&prompt.root; <userinput>service nfsclient start</userinput></screen>
<para>The client now has everything it needs to mount a remote
file system. In these examples, the server's name is
<systemitem>server</systemitem> and the client's name is
<systemitem>client</systemitem>. To mount
<filename>/home</filename> on
<systemitem>server</systemitem> to the
<filename>/mnt</filename> mount point on
<systemitem>client</systemitem>:</para>
<indexterm>
<primary>NFS</primary>
<secondary>mounting</secondary>
</indexterm>
<screen>&prompt.root; <userinput>mount server:/home /mnt</userinput></screen>
<para>The files and directories in
<filename>/home</filename> will now be available on
<systemitem>client</systemitem>, in the
<filename>/mnt</filename> directory.</para>
<para>To mount a remote file system each time the client boots,
add it to <filename>/etc/fstab</filename>:</para>
<programlisting>server:/home /mnt nfs rw 0 0</programlisting>
<para>Refer to &man.fstab.5; for a description of all available
options.</para>
</sect2>
<sect2>
<title>Locking</title>
<para>Some applications require file locking to operate
correctly. To enable locking, add these lines to
<filename>/etc/rc.conf</filename> on both the client and
server:</para>
<programlisting>rpc_lockd_enable="YES"
rpc_statd_enable="YES"</programlisting>
<para>Then start the applications:</para>
<screen>&prompt.root; <userinput>service lockd start</userinput>
&prompt.root; <userinput>service statd start</userinput></screen>
<para>If locking is not required on the server, the
<acronym>NFS</acronym> client can be configured to lock
locally by including <option>-L</option> when running
<application>mount</application>. Refer to &man.mount.nfs.8;
for further details.</para>
</sect2>
<sect2 xml:id="network-amd">
<info>
<title>Automating Mounts with &man.amd.8;</title>
<authorgroup>
<author>
<personname>
<firstname>Wylie</firstname>
<surname>Stilwell</surname>
</personname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<personname>
<firstname>Chern</firstname>
<surname>Lee</surname>
</personname>
<contrib>Rewritten by </contrib>
</author>
</authorgroup>
</info>
<indexterm><primary>amd</primary></indexterm>
<indexterm>
<primary>automatic mounter daemon</primary>
</indexterm>
<para>The automatic mounter daemon,
<application>amd</application>, automatically mounts a remote
file system whenever a file or directory within that file
system is accessed. File systems that are inactive for a
period of time will be automatically unmounted by
<application>amd</application>.</para>
<para>This daemon provides an alternative to modifying
<filename>/etc/fstab</filename> to list every client. It
operates by attaching itself as an <acronym>NFS</acronym>
server to the <filename>/host</filename> and
<filename>/net</filename> directories. When a file is
accessed within one of these directories,
<application>amd</application> looks up the corresponding
remote mount and automatically mounts it.
<filename>/net</filename> is used to mount an exported file
system from an <acronym>IP</acronym> address while
<filename>/host</filename> is used to mount an export from a
remote hostname. For instance, an attempt to access a file
within <filename>/host/foobar/usr</filename> would tell
<application>amd</application> to mount the
<filename>/usr</filename> export on the host
<systemitem>foobar</systemitem>.</para>
<example>
<title>Mounting an Export with
<application>amd</application></title>
<para>In this example, <command>showmount -e</command> shows
the exported file systems that can be mounted from the
<acronym>NFS</acronym> server,
<systemitem>foobar</systemitem>:</para>
<screen>&prompt.user; <userinput>showmount -e foobar</userinput>
Exports list on foobar:
/usr 10.10.10.0
/a 10.10.10.0
&prompt.user; <userinput>cd /host/foobar/usr</userinput></screen>
</example>
<para>The output from <command>showmount</command> shows
<filename>/usr</filename> as an export. When changing
directories to <filename>/host/foobar/usr</filename>,
<application>amd</application> intercepts the request and
attempts to resolve the hostname
<systemitem>foobar</systemitem>. If successful,
<application>amd</application> automatically mounts the
desired export.</para>
<para>To enable <application>amd</application> at boot time, add
this line to <filename>/etc/rc.conf</filename>:</para>
<programlisting>amd_enable="YES"</programlisting>
<para>To start <application>amd</application> now:</para>
<screen>&prompt.root; <userinput>service amd start</userinput></screen>
<para>Custom flags can be passed to
<application>amd</application> from the
<varname>amd_flags</varname> environment variable. By
default, <varname>amd_flags</varname> is set to:</para>
<programlisting>amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map"</programlisting>
<para>The default options with which exports are mounted are
defined in <filename>/etc/amd.map</filename>. Some of the
more advanced features of <application>amd</application> are
defined in <filename>/etc/amd.conf</filename>.</para>
<para>Consult &man.amd.8; and &man.amd.conf.5; for more
information.</para>
</sect2>
<sect2 xml:id="network-autofs">
<title>Automating Mounts with &man.autofs.5;</title>
<note>
<para>The &man.autofs.5; automount facility is supported
starting with &os;&nbsp;10.1-RELEASE. To use the
automounter functionality in older versions of &os;, use
&man.amd.8; instead. This chapter only describes the
&man.autofs.5; automounter.</para>
</note>
<indexterm><primary>autofs</primary></indexterm>
<indexterm>
<primary>automounter subsystem</primary>
</indexterm>
<para>The &man.autofs.5; facility is a common name for several
components that, together, allow for automatic mounting of
remote and local filesystems whenever a file or directory
within that file system is accessed. It consists of the
kernel component, &man.autofs.5;, and several userspace
applications: &man.automount.8;, &man.automountd.8; and
&man.autounmountd.8;. It serves as an alternative for
&man.amd.8; from previous &os; releases. Amd is still
provided for backward compatibility purposes, as the two use
different map format; the one used by autofs is the same as
with other SVR4 automounters, such as the ones in Solaris,
MacOS X, and Linux.</para>
<para>The &man.autofs.5; virtual filesystem is mounted on
specified mountpoints by &man.automount.8;, usually invoked
during boot.</para>
<para>Whenever a process attempts to access file within the
&man.autofs.5; mountpoint, the kernel will notify
&man.automountd.8; daemon and pause the triggering process.
The &man.automountd.8; daemon will handle kernel requests by
finding the proper map and mounting the filesystem according
to it, then signal the kernel to release blocked process. The
&man.autounmountd.8; daemon automatically unmounts automounted
filesystems after some time, unless they are still being
used.</para>
<para>The primary autofs configuration file is
<filename>/etc/auto_master</filename>. It assigns individual
maps to top-level mounts. For an explanation of
<filename>auto_master</filename> and the map syntax, refer to
&man.auto.master.5;.</para>
<para>There is a special automounter map mounted on
<filename>/net</filename>. When a file is accessed within
this directory, &man.autofs.5; looks up the corresponding
remote mount and automatically mounts it. For instance, an
attempt to access a file within
<filename>/net/foobar/usr</filename> would tell
&man.automountd.8; to mount the <filename
>/usr</filename> export from the host
<systemitem class="fqdomainname">foobar</systemitem>.</para>
<example>
<title>Mounting an Export with &man.autofs.5;</title>
<para>In this example, <command>showmount -e</command> shows
the exported file systems that can be mounted from the
<acronym>NFS</acronym> server,
<systemitem class="fqdomainname">foobar</systemitem>:</para>
<screen>&prompt.user; <userinput>showmount -e foobar</userinput>
Exports list on foobar:
/usr 10.10.10.0
/a 10.10.10.0
&prompt.user; <userinput>cd /net/foobar/usr</userinput></screen>
</example>
<para>The output from <command>showmount</command> shows
<filename>/usr</filename> as an export.
When changing directories to <filename
>/host/foobar/usr</filename>,
&man.automountd.8; intercepts the request and attempts to
resolve the hostname <systemitem
class="fqdomainname">foobar</systemitem>. If successful,
&man.automountd.8; automatically mounts the source
export.</para>
<para>To enable &man.autofs.5; at boot time, add this line to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>autofs_enable="YES"</programlisting>
<para>Then &man.autofs.5; can be started by running:</para>
<screen>&prompt.root; <userinput>service automount start</userinput>
&prompt.root; <userinput>service automountd start</userinput>
&prompt.root; <userinput>service autounmountd start</userinput></screen>
<para>The &man.autofs.5; map format is the same as in other
operating systems. Information about this format from other
sources can be useful, like the <link
xlink:href="http://web.archive.org/web/20160813071113/http://images.apple.com/business/docs/Autofs.pdf">Mac
OS X document</link>.</para>
<para>Consult the &man.automount.8;, &man.automountd.8;,
&man.autounmountd.8;, and &man.auto.master.5; manual pages for
more information.</para>
</sect2>
</sect1>
<sect1 xml:id="network-nis">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Bill</firstname>
<surname>Swingle</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<firstname>Eric</firstname>
<surname>Ogren</surname>
<contrib>Enhanced by </contrib>
</author>
<author>
<firstname>Udo</firstname>
<surname>Erdelhoff</surname>
</author>
</authorgroup>
</sect1info>
-->
<title>Network Information System
(<acronym>NIS</acronym>)</title>
<indexterm><primary>NIS</primary></indexterm>
<indexterm><primary>Solaris</primary></indexterm>
<indexterm><primary>HP-UX</primary></indexterm>
<indexterm><primary>AIX</primary></indexterm>
<indexterm><primary>Linux</primary></indexterm>
<indexterm><primary>NetBSD</primary></indexterm>
<indexterm><primary>OpenBSD</primary></indexterm>
<indexterm>
<primary>yellow pages</primary>
<see>NIS</see>
</indexterm>
<para>Network Information System (<acronym>NIS</acronym>) is
designed to centralize administration of &unix;-like systems
such as &solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, and
&os;. <acronym>NIS</acronym> was originally known as Yellow
Pages but the name was changed due to trademark issues. This
is the reason why <acronym>NIS</acronym> commands begin with
<literal>yp</literal>.</para>
<indexterm>
<primary>NIS</primary>
<secondary>domains</secondary>
</indexterm>
<para><acronym>NIS</acronym> is a Remote Procedure Call
(<acronym>RPC</acronym>)-based client/server system that allows
a group of machines within an <acronym>NIS</acronym> domain to
share a common set of configuration files. This permits a
system administrator to set up <acronym>NIS</acronym> client
systems with only minimal configuration data and to add, remove,
or modify configuration data from a single location.</para>
<para>&os; uses version 2 of the <acronym>NIS</acronym>
protocol.</para>
<sect2>
<title><acronym>NIS</acronym> Terms and Processes</title>
<para>Table 28.1 summarizes the terms and important processes
used by <acronym>NIS</acronym>:</para>
<indexterm>
<primary><application>rpcbind</application></primary>
</indexterm>
<indexterm>
<primary><application>portmap</application></primary>
</indexterm>
<table frame="none" pgwide="1">
<title><acronym>NIS</acronym> Terminology</title>
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Term</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><acronym>NIS</acronym> domain name</entry>
<entry><acronym>NIS</acronym> servers and clients share
an <acronym>NIS</acronym> domain name. Typically,
this name does not have anything to do with
<acronym>DNS</acronym>.</entry>
</row>
<row>
<entry>&man.rpcbind.8;</entry>
<entry>This service enables <acronym>RPC</acronym> and
must be running in order to run an
<acronym>NIS</acronym> server or act as an
<acronym>NIS</acronym> client.</entry>
</row>
<row>
<entry>&man.ypbind.8;</entry>
<entry>This service binds an <acronym>NIS</acronym>
client to its <acronym>NIS</acronym> server. It will
take the <acronym>NIS</acronym> domain name and use
<acronym>RPC</acronym> to connect to the server. It
is the core of client/server communication in an
<acronym>NIS</acronym> environment. If this service
is not running on a client machine, it will not be
able to access the <acronym>NIS</acronym>
server.</entry>
</row>
<row>
<entry>&man.ypserv.8;</entry>
<entry>This is the process for the
<acronym>NIS</acronym> server. If this service stops
running, the server will no longer be able to respond
to <acronym>NIS</acronym> requests so hopefully, there
is a slave server to take over. Some non-&os; clients
will not try to reconnect using a slave server and the
<application>ypbind</application> process may need to
be restarted on these
clients.</entry>
</row>
<row>
<entry>&man.rpc.yppasswdd.8;</entry>
<entry>This process only runs on
<acronym>NIS</acronym> master servers. This daemon
allows <acronym>NIS</acronym> clients to change their
<acronym>NIS</acronym> passwords. If this daemon is
not running, users will have to login to the
<acronym>NIS</acronym> master server and change their
passwords there.</entry>
</row>
</tbody>
</tgroup>
</table>
<!-- XXX Missing: rpc.ypxfrd (not important, though) May only run
on the master -->
</sect2>
<sect2>
<title>Machine Types</title>
<indexterm><primary>NIS</primary>
<secondary>master server</secondary>
</indexterm>
<indexterm><primary>NIS</primary>
<secondary>slave server</secondary>
</indexterm>
<indexterm><primary>NIS</primary>
<secondary>client</secondary>
</indexterm>
<para>There are three types of hosts in an
<acronym>NIS</acronym> environment:</para>
<itemizedlist>
<listitem>
<para><acronym>NIS</acronym> master server</para>
<para>This server acts as a central repository for host
configuration information and maintains the
authoritative copy of the files used by all of the
<acronym>NIS</acronym> clients. The
<filename>passwd</filename>, <filename>group</filename>,
and other various files used by <acronym>NIS</acronym>
clients are stored on the master server. While it is
possible for one machine to be an <acronym>NIS</acronym>
master server for more than one <acronym>NIS</acronym>
domain, this type of configuration will not be covered in
this chapter as it assumes a relatively small-scale
<acronym>NIS</acronym> environment.</para>
</listitem>
<listitem>
<para><acronym>NIS</acronym> slave servers</para>
<para><acronym>NIS</acronym> slave servers maintain copies
of the <acronym>NIS</acronym> master's data files in
order to provide redundancy. Slave servers also help to
balance the load of the master server as
<acronym>NIS</acronym> clients always attach to the
<acronym>NIS</acronym> server which responds
first.</para>
</listitem>
<listitem>
<para><acronym>NIS</acronym> clients</para>
<para><acronym>NIS</acronym> clients authenticate
against the <acronym>NIS</acronym> server during log
on.</para>
</listitem>
</itemizedlist>
<para>Information in many files can be shared using
<acronym>NIS</acronym>. The
<filename>master.passwd</filename>,
<filename>group</filename>, and <filename>hosts</filename>
files are commonly shared via <acronym>NIS</acronym>.
Whenever a process on a client needs information that would
normally be found in these files locally, it makes a query to
the <acronym>NIS</acronym> server that it is bound to
instead.</para>
</sect2>
<sect2>
<title>Planning Considerations</title>
<para>This section describes a sample <acronym>NIS</acronym>
environment which consists of 15 &os; machines with no
centralized point of administration. Each machine has its own
<filename>/etc/passwd</filename> and
<filename>/etc/master.passwd</filename>. These files are kept
in sync with each other only through manual intervention.
Currently, when a user is added to the lab, the process must
be repeated on all 15 machines.</para>
<para>The configuration of the lab will be as follows:</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="3">
<thead>
<row>
<entry>Machine name</entry>
<entry><acronym>IP</acronym> address</entry>
<entry>Machine role</entry>
</row>
</thead>
<tbody>
<row>
<entry><systemitem>ellington</systemitem></entry>
<entry><systemitem
class="ipaddress">10.0.0.2</systemitem></entry>
<entry><acronym>NIS</acronym> master</entry>
</row>
<row>
<entry><systemitem>coltrane</systemitem></entry>
<entry><systemitem
class="ipaddress">10.0.0.3</systemitem></entry>
<entry><acronym>NIS</acronym> slave</entry>
</row>
<row>
<entry><systemitem>basie</systemitem></entry>
<entry><systemitem
class="ipaddress">10.0.0.4</systemitem></entry>
<entry>Faculty workstation</entry>
</row>
<row>
<entry><systemitem>bird</systemitem></entry>
<entry><systemitem
class="ipaddress">10.0.0.5</systemitem></entry>
<entry>Client machine</entry>
</row>
<row>
<entry><systemitem>cli[1-11]</systemitem></entry>
<entry>
<systemitem
class="ipaddress">10.0.0.[6-17]</systemitem></entry>
<entry>Other client machines</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>If this is the first time an <acronym>NIS</acronym>
scheme is being developed, it should be thoroughly planned
ahead of time. Regardless of network size, several decisions
need to be made as part of the planning process.</para>
<sect3>
<title>Choosing a <acronym>NIS</acronym> Domain Name</title>
<indexterm>
<primary>NIS</primary>
<secondary>domain name</secondary>
</indexterm>
<para>When a client broadcasts its requests for info, it
includes the name of the <acronym>NIS</acronym> domain that
it is part of. This is how multiple servers on one network
can tell which server should answer which request. Think of
the <acronym>NIS</acronym> domain name as the name for a
group of hosts.</para>
<para>Some organizations choose to use their Internet domain
name for their <acronym>NIS</acronym> domain name. This is
not recommended as it can cause confusion when trying to
debug network problems. The <acronym>NIS</acronym> domain
name should be unique within the network and it is helpful
if it describes the group of machines it represents. For
example, the Art department at Acme Inc. might be in the
<quote>acme-art</quote> <acronym>NIS</acronym> domain. This
example will use the domain name
<literal>test-domain</literal>.</para>
<para>However, some non-&os; operating systems require the
<acronym>NIS</acronym> domain name to be the same as the
Internet domain name. If one or more machines on the
network have this restriction, the Internet domain name
<emphasis>must</emphasis> be used as the
<acronym>NIS</acronym> domain name.</para>
</sect3>
<sect3>
<title>Physical Server Requirements</title>
<para>There are several things to keep in mind when choosing a
machine to use as a <acronym>NIS</acronym> server. Since
<acronym>NIS</acronym> clients depend upon the availability
of the server, choose a machine that is not rebooted
frequently. The <acronym>NIS</acronym> server should
ideally be a stand alone machine whose sole purpose is to be
an <acronym>NIS</acronym> server. If the network is not
heavily used, it is acceptable to put the
<acronym>NIS</acronym> server on a machine running other
services. However, if the <acronym>NIS</acronym> server
becomes unavailable, it will adversely affect all
<acronym>NIS</acronym> clients.</para>
</sect3>
</sect2>
<sect2>
<title>Configuring the <acronym>NIS</acronym> Master
Server</title>
<para>The canonical copies of all <acronym>NIS</acronym> files
are stored on the master server. The databases used to store
the information are called <acronym>NIS</acronym> maps. In
&os;, these maps are stored in
<filename>/var/yp/[domainname]</filename> where
<filename>[domainname]</filename> is the name of the
<acronym>NIS</acronym> domain. Since multiple domains are
supported, it is possible to have several directories, one for
each domain. Each domain will have its own independent set of
maps.</para>
<para><acronym>NIS</acronym> master and slave servers handle all
<acronym>NIS</acronym> requests through &man.ypserv.8;. This
daemon is responsible for receiving incoming requests from
<acronym>NIS</acronym> clients, translating the requested
domain and map name to a path to the corresponding database
file, and transmitting data from the database back to the
client.</para>
<indexterm><primary>NIS</primary>
<secondary>server configuration</secondary>
</indexterm>
<para>Setting up a master <acronym>NIS</acronym> server can be
relatively straight forward, depending on environmental needs.
Since &os; provides built-in <acronym>NIS</acronym> support,
it only needs to be enabled by adding the following lines to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>nisdomainname="test-domain" <co xml:id="network-nis-co-domainname" />
nis_server_enable="YES" <co xml:id="network-nis-co-server" />
nis_yppasswdd_enable="YES" <co xml:id="network-nis-co-yppasswdd" /></programlisting>
<calloutlist>
<callout arearefs="network-nis-co-domainname">
<para>This line sets the <acronym>NIS</acronym> domain name
to <literal>test-domain</literal>.</para>
</callout>
<callout arearefs="network-nis-co-server">
<para>This automates the start up of the
<acronym>NIS</acronym> server processes when the system
boots.</para>
</callout>
<callout arearefs="network-nis-co-yppasswdd">
<para>This enables the &man.rpc.yppasswdd.8; daemon so that
users can change their <acronym>NIS</acronym> password
from a client machine.</para>
</callout>
</calloutlist>
<para>Care must be taken in a multi-server domain where the
server machines are also <acronym>NIS</acronym> clients. It
is generally a good idea to force the servers to bind to
themselves rather than allowing them to broadcast bind
requests and possibly become bound to each other. Strange
failure modes can result if one server goes down and others
are dependent upon it. Eventually, all the clients will time
out and attempt to bind to other servers, but the delay
involved can be considerable and the failure mode is still
present since the servers might bind to each other all over
again.</para>
<para>A server that is also a client can be forced to bind to a
particular server by adding these additional lines to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>nis_client_enable="YES" # run client stuff as well
nis_client_flags="-S <replaceable>NIS domain</replaceable>,<replaceable>server</replaceable>"</programlisting>
<para>After saving the edits, type
<command>/etc/netstart</command> to restart the network and
apply the values defined in <filename>/etc/rc.conf</filename>.
Before initializing the <acronym>NIS</acronym> maps, start
&man.ypserv.8;:</para>
<screen>&prompt.root; <userinput>service ypserv start</userinput></screen>
<sect3>
<title>Initializing the <acronym>NIS</acronym> Maps</title>
<indexterm>
<primary>NIS</primary>
<secondary>maps</secondary>
</indexterm>
<para><acronym>NIS</acronym> maps are generated from the
configuration files in <filename>/etc</filename> on the
<acronym>NIS</acronym> master, with one exception:
<filename>/etc/master.passwd</filename>. This is to prevent
the propagation of passwords to all the servers in the
<acronym>NIS</acronym> domain. Therefore, before the
<acronym>NIS</acronym> maps are initialized, configure the
primary password files:</para>
<screen>&prompt.root; <userinput>cp /etc/master.passwd /var/yp/master.passwd</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>vi master.passwd</userinput></screen>
<para>It is advisable to remove all entries for system
accounts as well as any user accounts that do not need to be
propagated to the <acronym>NIS</acronym> clients, such as
the <systemitem class="username">root</systemitem> and any
other administrative accounts.</para>
<note>
<para>Ensure that the
<filename>/var/yp/master.passwd</filename> is neither
group or world readable by setting its permissions to
<literal>600</literal>.</para>
</note>
<para>After completing this task, initialize the
<acronym>NIS</acronym> maps. &os; includes the
&man.ypinit.8; script to do this. When generating maps
for the master server, include <option>-m</option> and
specify the <acronym>NIS</acronym> domain name:</para>
<screen>ellington&prompt.root; <userinput>ypinit -m test-domain</userinput>
Server Type: MASTER Domain: test-domain
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] <userinput>n</userinput>
Ok, please remember to go back and redo manually whatever fails.
If not, something might not work.
At this point, we have to construct a list of this domains YP servers.
rod.darktech.org is already known as master server.
Please continue to add any slave servers, one per line. When you are
done with the list, type a &lt;control D&gt;.
master server : ellington
next host to add: <userinput>coltrane</userinput>
next host to add: <userinput>^D</userinput>
The current list of NIS servers looks like this:
ellington
coltrane
Is this correct? [y/n: y] <userinput>y</userinput>
[..output from map generation..]
NIS Map update completed.
ellington has been setup as an YP master server without any errors.</screen>
<para>This will create <filename>/var/yp/Makefile</filename>
from <filename>/var/yp/Makefile.dist</filename>. By
default, this file assumes that the environment has a
single <acronym>NIS</acronym> server with only &os; clients.
Since <literal>test-domain</literal> has a slave server,
edit this line in <filename>/var/yp/Makefile</filename> so
that it begins with a comment
(<literal>#</literal>):</para>
<programlisting>NOPUSH = "True"</programlisting>
</sect3>
<sect3>
<title>Adding New Users</title>
<para>Every time a new user is created, the user account must
be added to the master <acronym>NIS</acronym> server and the
<acronym>NIS</acronym> maps rebuilt. Until this occurs, the
new user will not be able to login anywhere except on the
<acronym>NIS</acronym> master. For example, to add the new
user <systemitem class="username">jsmith</systemitem> to the
<literal>test-domain</literal> domain, run these commands on
the master server:</para>
<screen>&prompt.root; <userinput>pw useradd jsmith</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>make test-domain</userinput></screen>
<para>The user could also be added using <command>adduser
jsmith</command> instead of <command>pw useradd
smith</command>.</para>
</sect3>
</sect2>
<sect2>
<title>Setting up a <acronym>NIS</acronym> Slave Server</title>
<indexterm>
<primary>NIS</primary>
<secondary>slave server</secondary>
</indexterm>
<para>To set up an <acronym>NIS</acronym> slave server, log on
to the slave server and edit <filename>/etc/rc.conf</filename>
as for the master server. Do not generate any
<acronym>NIS</acronym> maps, as these already exist on the
master server. When running <command>ypinit</command> on the
slave server, use <option>-s</option> (for slave) instead of
<option>-m</option> (for master). This option requires the
name of the <acronym>NIS</acronym> master in addition to the
domain name, as seen in this example:</para>
<screen>coltrane&prompt.root; <userinput>ypinit -s ellington test-domain</userinput>
Server Type: SLAVE Domain: test-domain Master: ellington
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] <userinput>n</userinput>
Ok, please remember to go back and redo manually whatever fails.
If not, something might not work.
There will be no further questions. The remainder of the procedure
should take a few minutes, to copy the databases from ellington.
Transferring netgroup...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byuser...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byhost...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring group.bygid...
ypxfr: Exiting: Map successfully transferred
Transferring group.byname...
ypxfr: Exiting: Map successfully transferred
Transferring services.byname...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.byname...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.byname...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring netid.byname...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring ypservers...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byname...
ypxfr: Exiting: Map successfully transferred
coltrane has been setup as an YP slave server without any errors.
Remember to update map ypservers on ellington.</screen>
<para>This will generate a directory on the slave server called
<filename>/var/yp/test-domain</filename> which contains copies
of the <acronym>NIS</acronym> master server's maps. Adding
these <filename>/etc/crontab</filename> entries on each slave
server will force the slaves to sync their maps with the maps
on the master server:</para>
<programlisting>20 * * * * root /usr/libexec/ypxfr passwd.byname
21 * * * * root /usr/libexec/ypxfr passwd.byuid</programlisting>
<para>These entries are not mandatory because the master server
automatically attempts to push any map changes to its slaves.
However, since clients may depend upon the slave server to
provide correct password information, it is recommended to
force frequent password map updates. This is especially
important on busy networks where map updates might not always
complete.</para>
<para>To finish the configuration, run
<command>/etc/netstart</command> on the slave server in order
to start the <acronym>NIS</acronym> services.</para>
</sect2>
<sect2>
<title>Setting Up an <acronym>NIS</acronym> Client</title>
<para>An <acronym>NIS</acronym> client binds to an
<acronym>NIS</acronym> server using &man.ypbind.8;. This
daemon broadcasts RPC requests on the local network. These
requests specify the domain name configured on the client. If
an <acronym>NIS</acronym> server in the same domain receives
one of the broadcasts, it will respond to
<application>ypbind</application>, which will record the
server's address. If there are several servers available,
the client will use the address of the first server to respond
and will direct all of its <acronym>NIS</acronym> requests to
that server. The client will automatically
<application>ping</application> the server on a regular basis
to make sure it is still available. If it fails to receive a
reply within a reasonable amount of time,
<application>ypbind</application> will mark the domain as
unbound and begin broadcasting again in the hopes of locating
another server.</para>
<indexterm><primary>NIS</primary>
<secondary>client configuration</secondary>
</indexterm>
<para>To configure a &os; machine to be an
<acronym>NIS</acronym> client:</para>
<procedure>
<step>
<para>Edit <filename>/etc/rc.conf</filename> and add the
following lines in order to set the
<acronym>NIS</acronym> domain name and start
&man.ypbind.8; during network startup:</para>
<programlisting>nisdomainname="test-domain"
nis_client_enable="YES"</programlisting>
</step>
<step>
<para>To import all possible password entries from the
<acronym>NIS</acronym> server, use
<command>vipw</command> to remove all user accounts
except one from <filename>/etc/master.passwd</filename>.
When removing the accounts, keep in mind that at least one
local account should remain and this account should be a
member of <systemitem
class="groupname">wheel</systemitem>. If there is a
problem with <acronym>NIS</acronym>, this local account
can be used to log in remotely, become the superuser, and
fix the problem. Before saving the edits, add the
following line to the end of the file:</para>
<programlisting>+:::::::::</programlisting>
<para>This line configures the client to provide anyone with
a valid account in the <acronym>NIS</acronym> server's
password maps an account on the client. There are many
ways to configure the <acronym>NIS</acronym> client by
modifying this line. One method is described in <xref
linkend="network-netgroups"/>. For more detailed
reading, refer to the book
<literal>Managing NFS and NIS</literal>, published by
O'Reilly Media.</para>
</step>
<step>
<para>To import all possible group entries from the
<acronym>NIS</acronym> server, add this line to
<filename>/etc/group</filename>:</para>
<programlisting>+:*::</programlisting>
</step>
</procedure>
<para>To start the <acronym>NIS</acronym> client immediately,
execute the following commands as the superuser:</para>
<screen>&prompt.root; <userinput>/etc/netstart</userinput>
&prompt.root; <userinput>service ypbind start</userinput></screen>
<para>After completing these steps, running
<command>ypcat passwd</command> on the client should show
the server's <filename>passwd</filename> map.</para>
</sect2>
<sect2>
<title><acronym>NIS</acronym> Security</title>
<para>Since <acronym>RPC</acronym> is a broadcast-based service,
any system running <application>ypbind</application> within
the same domain can retrieve the contents of the
<acronym>NIS</acronym> maps. To prevent unauthorized
transactions, &man.ypserv.8; supports a feature called
<quote>securenets</quote> which can be used to restrict access
to a given set of hosts. By default, this information is
stored in <filename>/var/yp/securenets</filename>, unless
&man.ypserv.8; is started with <option>-p</option> and an
alternate path. This file contains entries that consist of a
network specification and a network mask separated by white
space. Lines starting with <literal>#</literal> are
considered to be comments. A sample
<filename>securenets</filename> might look like this:</para>
<programlisting># allow connections from local host -- mandatory
127.0.0.1 255.255.255.255
# allow connections from any host
# on the 192.168.128.0 network
192.168.128.0 255.255.255.0
# allow connections from any host
# between 10.0.0.0 to 10.0.15.255
# this includes the machines in the testlab
10.0.0.0 255.255.240.0</programlisting>
<para>If &man.ypserv.8; receives a request from an address that
matches one of these rules, it will process the request
normally. If the address fails to match a rule, the request
will be ignored and a warning message will be logged. If the
<filename>securenets</filename> does not exist,
<command>ypserv</command> will allow connections from any
host.</para>
<para><xref linkend="tcpwrappers"/> is an alternate mechanism
for providing access control instead of
<filename>securenets</filename>. While either access control
mechanism adds some security, they are both vulnerable to
<quote><acronym>IP</acronym> spoofing</quote> attacks. All
<acronym>NIS</acronym>-related traffic should be blocked at
the firewall.</para>
<para>Servers using <filename>securenets</filename>
may fail to serve legitimate <acronym>NIS</acronym> clients
with archaic TCP/IP implementations. Some of these
implementations set all host bits to zero when doing
broadcasts or fail to observe the subnet mask when
calculating the broadcast address. While some of these
problems can be fixed by changing the client configuration,
other problems may force the retirement of these client
systems or the abandonment of
<filename>securenets</filename>.</para>
<indexterm><primary>TCP Wrapper</primary></indexterm>
<para>The use of <application>TCP Wrapper</application>
increases the latency of the <acronym>NIS</acronym> server.
The additional delay may be long enough to cause timeouts in
client programs, especially in busy networks with slow
<acronym>NIS</acronym> servers. If one or more clients suffer
from latency, convert those clients into
<acronym>NIS</acronym> slave servers and force them to bind to
themselves.</para>
<sect3>
<title>Barring Some Users</title>
<para>In this example, the <systemitem>basie</systemitem>
system is a faculty workstation within the
<acronym>NIS</acronym> domain. The
<filename>passwd</filename> map on the master
<acronym>NIS</acronym> server contains accounts for both
faculty and students. This section demonstrates how to
allow faculty logins on this system while refusing student
logins.</para>
<para>To prevent specified users from logging on to a system,
even if they are present in the <acronym>NIS</acronym>
database, use <command>vipw</command> to add
<literal>-<replaceable>username</replaceable></literal> with
the correct number of colons towards the end of
<filename>/etc/master.passwd</filename> on the client,
where <replaceable>username</replaceable> is the username of
a user to bar from logging in. The line with the blocked
user must be before the <literal>+</literal> line that
allows <acronym>NIS</acronym> users. In this example,
<systemitem class="username">bill</systemitem> is barred
from logging on to <systemitem>basie</systemitem>:</para>
<screen>basie&prompt.root; <userinput>cat /etc/master.passwd</userinput>
root:[password]:0:0::0:0:The super-user:/root:/bin/csh
toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh
daemon:*:1:1::0:0:Owner of many system processes:/root:/sbin/nologin
operator:*:2:5::0:0:System &amp;:/:/sbin/nologin
bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/sbin/nologin
tty:*:4:65533::0:0:Tty Sandbox:/:/sbin/nologin
kmem:*:5:65533::0:0:KMem Sandbox:/:/sbin/nologin
games:*:7:13::0:0:Games pseudo-user:/usr/games:/sbin/nologin
news:*:8:8::0:0:News Subsystem:/:/sbin/nologin
man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/sbin/nologin
bind:*:53:53::0:0:Bind Sandbox:/:/sbin/nologin
uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico
xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/sbin/nologin
pop:*:68:6::0:0:Post Office Owner:/nonexistent:/sbin/nologin
nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin
-bill:::::::::
+:::::::::
basie&prompt.root;</screen>
</sect3>
</sect2>
<sect2 xml:id="network-netgroups">
<!--
<sect2info>
<authorgroup>
<author>
<firstname>Udo</firstname>
<surname>Erdelhoff</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect2info>
-->
<title>Using Netgroups</title>
<indexterm><primary>netgroups</primary></indexterm>
<para>Barring specified users from logging on to individual
systems becomes unscaleable on larger networks and quickly
loses the main benefit of <acronym>NIS</acronym>:
<emphasis>centralized</emphasis> administration.</para>
<para>Netgroups were developed to handle large, complex networks
with hundreds of users and machines. Their use is comparable
to &unix; groups, where the main difference is the lack of a
numeric ID and the ability to define a netgroup by including
both user accounts and other netgroups.</para>
<para>To expand on the example used in this chapter, the
<acronym>NIS</acronym> domain will be extended to add the
users and systems shown in Tables 28.2 and 28.3:</para>
<table frame="none" pgwide="1">
<title>Additional Users</title>
<tgroup cols="2">
<thead>
<row>
<entry>User Name(s)</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><systemitem class="username">alpha</systemitem>,
<systemitem class="username">beta</systemitem></entry>
<entry>IT department employees</entry>
</row>
<row>
<entry><systemitem
class="username">charlie</systemitem>, <systemitem
class="username">delta</systemitem></entry>
<entry>IT department apprentices</entry>
</row>
<row>
<entry><systemitem class="username">echo</systemitem>,
<systemitem class="username">foxtrott</systemitem>,
<systemitem class="username">golf</systemitem>,
...</entry>
<entry>employees</entry>
</row>
<row>
<entry><systemitem class="username">able</systemitem>,
<systemitem class="username">baker</systemitem>,
...</entry>
<entry>interns</entry>
</row>
</tbody>
</tgroup>
</table>
<table frame="none" pgwide="1">
<title>Additional Systems</title>
<tgroup cols="2">
<thead>
<row>
<entry>Machine Name(s)</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<!-- Names taken from "Good Omens" by Neil Gaiman and Terry
Pratchett. Many thanks for a brilliant book. -->
<entry><systemitem>war</systemitem>,
<systemitem>death</systemitem>,
<systemitem>famine</systemitem>,
<systemitem>pollution</systemitem></entry>
<entry>Only IT employees are allowed to log onto these
servers.</entry>
</row>
<row>
<!-- gluttony was omitted because it was too fat -->
<entry><systemitem>pride</systemitem>,
<systemitem>greed</systemitem>,
<systemitem>envy</systemitem>,
<systemitem>wrath</systemitem>,
<systemitem>lust</systemitem>,
<systemitem>sloth</systemitem></entry>
<entry>All members of the IT department are allowed to
login onto these servers.</entry>
</row>
<row>
<entry><systemitem>one</systemitem>,
<systemitem>two</systemitem>,
<systemitem>three</systemitem>,
<systemitem>four</systemitem>,
...</entry>
<entry>Ordinary workstations used by
employees.</entry>
</row>
<row>
<entry><systemitem>trashcan</systemitem></entry>
<entry>A very old machine without any critical data.
Even interns are allowed to use this system.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>When using netgroups to configure this scenario, each user
is assigned to one or more netgroups and logins are then
allowed or forbidden for all members of the netgroup. When
adding a new machine, login restrictions must be defined for
all netgroups. When a new user is added, the account must be
added to one or more netgroups. If the
<acronym>NIS</acronym> setup is planned carefully, only one
central configuration file needs modification to grant or deny
access to machines.</para>
<para>The first step is the initialization of the
<acronym>NIS</acronym> <literal>netgroup</literal> map. In
&os;, this map is not created by default. On the
<acronym>NIS</acronym> master server, use an editor to create
a map named <filename>/var/yp/netgroup</filename>.</para>
<para>This example creates four netgroups to represent IT
employees, IT apprentices, employees, and interns:</para>
<programlisting>IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
USERS (,echo,test-domain) (,foxtrott,test-domain) \
(,golf,test-domain)
INTERNS (,able,test-domain) (,baker,test-domain)</programlisting>
<para>Each entry configures a netgroup. The first column in an
entry is the name of the netgroup. Each set of brackets
represents either a group of one or more users or the name of
another netgroup. When specifying a user, the three
comma-delimited fields inside each group represent:</para>
<orderedlist>
<listitem>
<para>The name of the host(s) where the other fields
representing the user are valid. If a hostname is not
specified, the entry is valid on all hosts.</para>
</listitem>
<listitem>
<para>The name of the account that belongs to this
netgroup.</para>
</listitem>
<listitem>
<para>The <acronym>NIS</acronym> domain for the account.
Accounts may be imported from other <acronym>NIS</acronym>
domains into a netgroup.</para>
</listitem>
</orderedlist>
<para>If a group contains multiple users, separate each user
with whitespace. Additionally, each field may contain
wildcards. See &man.netgroup.5; for details.</para>
<indexterm><primary>netgroups</primary></indexterm>
<para>Netgroup names longer than 8 characters should not be
used. The names are case sensitive and using capital letters
for netgroup names is an easy way to distinguish between user,
machine and netgroup names.</para>
<para>Some non-&os; <acronym>NIS</acronym> clients cannot
handle netgroups containing more than 15 entries. This
limit may be circumvented by creating several sub-netgroups
with 15 users or fewer and a real netgroup consisting of the
sub-netgroups, as seen in this example:</para>
<programlisting>BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...]
BIGGRP2 (,joe16,domain) (,joe17,domain) [...]
BIGGRP3 (,joe31,domain) (,joe32,domain)
BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3</programlisting>
<para>Repeat this process if more than 225 (15 times 15) users
exist within a single netgroup.</para>
<para>To activate and distribute the new
<acronym>NIS</acronym> map:</para>
<screen>ellington&prompt.root; <userinput>cd /var/yp</userinput>
ellington&prompt.root; <userinput>make</userinput></screen>
<para>This will generate the three <acronym>NIS</acronym> maps
<filename>netgroup</filename>,
<filename>netgroup.byhost</filename> and
<filename>netgroup.byuser</filename>. Use the map key option
of &man.ypcat.1; to check if the new <acronym>NIS</acronym>
maps are available:</para>
<screen>ellington&prompt.user; <userinput>ypcat -k netgroup</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byhost</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byuser</userinput></screen>
<para>The output of the first command should resemble the
contents of <filename>/var/yp/netgroup</filename>. The second
command only produces output if host-specific netgroups were
created. The third command is used to get the list of
netgroups for a user.</para>
<para>To configure a client, use &man.vipw.8; to specify the
name of the netgroup. For example, on the server named
<systemitem>war</systemitem>, replace this line:</para>
<programlisting>+:::::::::</programlisting>
<para>with</para>
<programlisting>+@IT_EMP:::::::::</programlisting>
<para>This specifies that only the users defined in the netgroup
<literal>IT_EMP</literal> will be imported into this system's
password database and only those users are allowed to login to
this system.</para>
<para>This configuration also applies to the
<literal>~</literal> function of the shell and all routines
which convert between user names and numerical user IDs. In
other words,
<command>cd ~<replaceable>user</replaceable></command> will
not work, <command>ls -l</command> will show the numerical ID
instead of the username, and <command>find . -user joe
-print</command> will fail with the message
<errorname>No such user</errorname>. To fix this, import all
user entries without allowing them to login into the servers.
This can be achieved by adding an extra line:</para>
<programlisting>+:::::::::/sbin/nologin</programlisting>
<para>This line configures the client to import all entries but
to replace the shell in those entries with
<filename>/sbin/nologin</filename>.</para>
<!-- Been there, done that, got the scars to prove it - ue -->
<para>Make sure that extra line is placed
<emphasis>after</emphasis>
<literal>+@IT_EMP:::::::::</literal>. Otherwise, all user
accounts imported from <acronym>NIS</acronym> will have
<filename>/sbin/nologin</filename> as their login
shell and no one will be able to login to the system.</para>
<para>To configure the less important servers, replace the old
<literal>+:::::::::</literal> on the servers with these
lines:</para>
<programlisting>+@IT_EMP:::::::::
+@IT_APP:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>The corresponding lines for the workstations
would be:</para>
<programlisting>+@IT_EMP:::::::::
+@USERS:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>NIS supports the creation of netgroups from other
netgroups which can be useful if the policy regarding user
access changes. One possibility is the creation of role-based
netgroups. For example, one might create a netgroup called
<literal>BIGSRV</literal> to define the login restrictions for
the important servers, another netgroup called
<literal>SMALLSRV</literal> for the less important servers,
and a third netgroup called <literal>USERBOX</literal> for the
workstations. Each of these netgroups contains the netgroups
that are allowed to login onto these machines. The new
entries for the <acronym>NIS</acronym>
<literal>netgroup</literal> map would look like this:</para>
<programlisting>BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERS</programlisting>
<para>This method of defining login restrictions works
reasonably well when it is possible to define groups of
machines with identical restrictions. Unfortunately, this is
the exception and not the rule. Most of the time, the ability
to define login restrictions on a per-machine basis is
required.</para>
<para>Machine-specific netgroup definitions are another
possibility to deal with the policy changes. In this
scenario, the <filename>/etc/master.passwd</filename> of each
system contains two lines starting with <quote>+</quote>.
The first line adds a netgroup with the accounts allowed to
login onto this machine and the second line adds all other
accounts with <filename>/sbin/nologin</filename> as shell. It
is recommended to use the <quote>ALL-CAPS</quote> version of
the hostname as the name of the netgroup:</para>
<programlisting>+@<replaceable>BOXNAME</replaceable>:::::::::
+:::::::::/sbin/nologin</programlisting>
<para>Once this task is completed on all the machines, there is
no longer a need to modify the local versions of
<filename>/etc/master.passwd</filename> ever again. All
further changes can be handled by modifying the
<acronym>NIS</acronym> map. Here is an example of a possible
<literal>netgroup</literal> map for this scenario:</para>
<programlisting># Define groups of users first
IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
DEPT1 (,echo,test-domain) (,foxtrott,test-domain)
DEPT2 (,golf,test-domain) (,hotel,test-domain)
DEPT3 (,india,test-domain) (,juliet,test-domain)
ITINTERN (,kilo,test-domain) (,lima,test-domain)
D_INTERNS (,able,test-domain) (,baker,test-domain)
#
# Now, define some groups based on roles
USERS DEPT1 DEPT2 DEPT3
BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERS
#
# And a groups for a special tasks
# Allow echo and golf to access our anti-virus-machine
SECURITY IT_EMP (,echo,test-domain) (,golf,test-domain)
#
# machine-based netgroups
# Our main servers
WAR BIGSRV
FAMINE BIGSRV
# User india needs access to this server
POLLUTION BIGSRV (,india,test-domain)
#
# This one is really important and needs more access restrictions
DEATH IT_EMP
#
# The anti-virus-machine mentioned above
ONE SECURITY
#
# Restrict a machine to a single user
TWO (,hotel,test-domain)
# [...more groups to follow]</programlisting>
<para>It may not always be advisable
to use machine-based netgroups. When deploying a couple of
dozen or hundreds of systems,
role-based netgroups instead of machine-based netgroups may be
used to keep the size of the <acronym>NIS</acronym> map within
reasonable limits.</para>
</sect2>
<sect2>
<title>Password Formats</title>
<indexterm>
<primary>NIS</primary>
<secondary>password formats</secondary>
</indexterm>
<para><acronym>NIS</acronym> requires that all hosts within an
<acronym>NIS</acronym> domain use the same format for
encrypting passwords. If users have trouble authenticating on
an <acronym>NIS</acronym> client, it may be due to a differing
password format. In a heterogeneous network, the format must
be supported by all operating systems, where
<acronym>DES</acronym> is the lowest common standard.</para>
<para>To check which format a server or client is using, look
at this section of
<filename>/etc/login.conf</filename>:</para>
<programlisting>default:\
:passwd_format=des:\
:copyright=/etc/COPYRIGHT:\
[Further entries elided]</programlisting>
<para>In this example, the system is using the
<acronym>DES</acronym> format. Other possible values are
<literal>blf</literal> for Blowfish and <literal>md5</literal>
for MD5 encrypted passwords.</para>
<para>If the format on a host needs to be edited to match the
one being used in the <acronym>NIS</acronym> domain, the
login capability database must be rebuilt after saving the
change:</para>
<screen>&prompt.root; <userinput>cap_mkdb /etc/login.conf</userinput></screen>
<note>
<para>The format of passwords for existing user accounts will
not be updated until each user changes their password
<emphasis>after</emphasis> the login capability database is
rebuilt.</para>
</note>
</sect2>
</sect1>
<sect1 xml:id="network-ldap">
<info>
<title>Lightweight Directory Access Protocol
(<acronym>LDAP</acronym>)</title>
<authorgroup>
<author>
<personname>
<firstname>Rocky</firstname>
<surname>Hotas</surname>
</personname>
<contrib>Updated by </contrib>
</author>
</authorgroup>
<authorgroup>
<author>
<personname>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
</personname>
<contrib>Originally contributed by </contrib>
</author>
</authorgroup>
</info>
<indexterm><primary>LDAP</primary></indexterm>
<para>The Lightweight Directory Access Protocol
(<acronym>LDAP</acronym>) is an application layer protocol used
to access, modify, and authenticate objects using a distributed
directory information service. Think of it as a phone or record
book which stores several levels of hierarchical, homogeneous
information. It is used in Active Directory and
<application>OpenLDAP</application> networks and allows users to
access to several levels of internal information utilizing a
single account. For example, email authentication, pulling
employee contact information, and internal website
authentication might all make use of a single user account in
the <acronym>LDAP</acronym> server's record base.</para>
<para>This section provides a quick start guide for configuring an
<acronym>LDAP</acronym> server on a &os; system. It assumes
that the administrator already has a design plan which includes
the type of information to store, what that information will be
used for, which users should have access to that information,
and how to secure this information from unauthorized
access.</para>
<sect2>
<title><acronym>LDAP</acronym> Terminology and Structure</title>
<para><acronym>LDAP</acronym> uses several terms which should be
understood before starting the configuration. All directory
entries consist of a group of
<firstterm>attributes</firstterm>. Each of these attribute
sets contains a unique identifier known as a
<firstterm>Distinguished Name</firstterm>
(<acronym>DN</acronym>) which is normally built from several
other attributes such as the common or
<firstterm>Relative Distinguished Name</firstterm>
(<acronym>RDN</acronym>). Similar to how directories have
absolute and relative paths, consider a <acronym>DN</acronym>
as an absolute path and the <acronym>RDN</acronym> as the
relative path.</para>
<para>An example <acronym>LDAP</acronym> entry looks like the
following. This example searches for the entry for the
specified user account (<literal>uid</literal>),
organizational unit (<literal>ou</literal>), and organization
(<literal>o</literal>):</para>
<screen>&prompt.user; <userinput>ldapsearch -xb "uid=<replaceable>trhodes</replaceable>,ou=<replaceable>users</replaceable>,o=<replaceable>example.com</replaceable>"</userinput>
# extended LDIF
#
# LDAPv3
# base &lt;uid=trhodes,ou=users,o=example.com&gt; with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# trhodes, users, example.com
dn: uid=trhodes,ou=users,o=example.com
mail: trhodes@example.com
cn: Tom Rhodes
uid: trhodes
telephoneNumber: (123) 456-7890
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1</screen>
<para>This example entry shows the values for the
<literal>dn</literal>, <literal>mail</literal>,
<literal>cn</literal>, <literal>uid</literal>, and
<literal>telephoneNumber</literal> attributes. The
<acronym>cn</acronym> attribute is the
<acronym>RDN</acronym>.</para>
<para>More information about <acronym>LDAP</acronym> and its
terminology can be found at <uri
xlink:href="http://www.openldap.org/doc/admin24/intro.html">http://www.openldap.org/doc/admin24/intro.html</uri>.</para>
</sect2>
<sect2 xml:id="ldap-config">
<title>Configuring an <acronym>LDAP</acronym> Server</title>
<indexterm><primary>LDAP Server</primary></indexterm>
<para>&os; does not provide a built-in <acronym>LDAP</acronym>
server. Begin the configuration by installing <package
role="port">net/openldap-server</package> package or
port:
<screen>&prompt.root; <userinput>pkg install openldap-server</userinput></screen>
There is a large set of default options enabled in
the <link
xlink:href="&url.articles.linux-users;/software.html">
package</link>. To review them:
<command>pkg info openldap-server</command>. If they are not
sufficient (for example if SQL support is needed), please
consider recompiling the port using the appropriate <link
xlink:href="&url.books.handbook;/ports-using.html">
framework</link>.</para>
<para>The installation creates the directory
<filename>/var/db/openldap-data</filename> to hold the data.
The directory to store the certificates must be
created:</para>
<screen>&prompt.root; <userinput>mkdir /usr/local/etc/openldap/private</userinput></screen>
<tip>
<para>Each host in a secure <acronym>LDAP</acronym> network
must exhibit a trusted certificate. A self signed
certificate must be obtained first: it is trusted either
because it has been bought, or because it has been created
by the system administrator. This certificate is called
<firstterm>root certificate</firstterm> or
<firstterm>Certificate Authority</firstterm>. It cannot
represent a host. It is used to sign the other
certificates: this way, they are trusted.</para>
</tip>
<para>The following commands must be executed from
<filename>/usr/local/etc/openldap/private</filename>. This
is important, as the file permissions need to be restrictive
and users should not have access to these files. To create
the Certificate Authority with &man.openssl.1;, start
with:</para>
<screen>&prompt.root; <userinput>openssl req -days <replaceable>365</replaceable> -nodes -new -x509 -keyout ca.key -out ../ca.crt</userinput></screen>
<para>The entries for the prompts may be arbitrary,
<emphasis>except</emphasis> for the
<literal>Common Name</literal>: it is the hostname, by a
non-mandatory convention, for a host certificate.
But the root certificate does not represent a host and it
<emphasis>must</emphasis> have a different <literal>Common
Name</literal>: here, <literal>CAdomain.example</literal>
will be used.</para>
<para>The next task is to create the <acronym>LDAP</acronym>
server certificate. Input this command and follow the prompts
again:</para>
<screen>&prompt.root; <userinput>openssl req -days <replaceable>365</replaceable> -nodes -new -keyout server.key -out server.csr</userinput></screen>
<para>Use the server hostname <systemitem
class="systemname">domain.example</systemitem> as
<literal>Common Name</literal>.
This is a <firstterm>Certificate Signing Request</firstterm>.
It must be signed with the Certificate Authority to be used as
a valid certificate:</para>
<screen>&prompt.root; <userinput>openssl x509 -req -days <replaceable>365</replaceable> -in server.csr -out ../server.crt -CA ../ca.crt -CAkey ca.key -CAcreateserial</userinput></screen>
<para>The client certificate must be now created and signed.
If it is the <emphasis>same</emphasis> machine as the server,
the <emphasis>same</emphasis> <literal>Common Name</literal>
must be used:</para>
<screen>&prompt.root; <userinput>openssl req -days <replaceable>365</replaceable> -nodes -new -keyout client.key -out client.csr</userinput>
&prompt.root; <userinput>openssl x509 -req -days <replaceable>365</replaceable> -in client.csr -out ../client.crt -CA ../ca.crt -CAkey ca.key</userinput></screen>
<para>When finished, be sure that eight new files have been
created: the certificates <filename>ca.crt</filename>,
<filename>server.crt</filename> and
<filename>client.crt</filename> in
<filename>/usr/local/etc/openldap</filename> and
<filename>ca.key</filename>,
<filename>client.csr</filename>,
<filename>client.key</filename>,
<filename>server.csr</filename>,
<filename>server.key</filename> in
<filename>/usr/local/etc/openldap/private</filename>. Further
information about this procedure can be found in
&man.openssl.1;, <link
xlink:href="https://www.freebsd.org/cgi/man.cgi?query=req&amp;manpath=FreeBSD+11.0-RELEASE+and+Ports">req(1)</link>
and in the <link
xlink:href="http://www.openldap.org/doc/admin24/tls.html">
OpenLDAP 2.4 Administrator's Guide</link>.</para>
<para>The daemon running the OpenLDAP server is called
<filename>slapd</filename> and it must be configured.
Such a configuration can be performed in two ways: through a
<filename>slapd.conf</filename> configuration file, or
through a database file <filename>slapd.ldif</filename>.
The former way is deprecated by OpenLDAP:</para>
<tip>
<para>The use of <filename>slapd.ldif</filename> is
strongly recommended.</para>
</tip>
<para>The structure of this file is not trivial. A
configuration example can be found <link xlink:href=
"http://www.openldap.org/doc/admin24/slapdconf2.html">
here</link>, in paragraph 5.3. The directory
<filename>/usr/local/etc/openldap</filename> contains a file
named <filename>slapd.ldif.sample</filename> in order to
ease the configuration.
A full example of the <filename>slapd.ldif</filename> will
be provided below, with some comments. The file is composed
by several parts: each of them is uniquely identified
through a <literal>dn:</literal> (Distinguished Name). The
first one is the <emphasis>global configuration</emphasis>
entry. Be sure that no blank lines are between the
<literal>dn:</literal> statement and the desired end of the
section, otherwise an error will be generated. In the global
section, options regarding the execution of <filename>
slapd</filename> and security can be specified. The
statements are generally the same as in <filename>
slapd.conf</filename>, but preceded by "<literal>
olc</literal>". The beginning of the <filename>
slapd.ldif</filename> configuration file is reported here:
in this section, the certificate file, its key, and the
Certificate Authority file should be specificed, if a secure
connection for communcations is required. In this example,
TLS will be used to implement a secure channel. All the
following options (and more) are documented in <link
xlink:href="https://www.freebsd.org/cgi/man.cgi?query=slapd-config&amp;manpath=FreeBSD+11.0-RELEASE+and+Ports">
slapd-config(5)</link>, which is recommended to be consulted
during configuration. The following file is intended to work
with the suggested TLS configuration.</para>
<programlisting>#
# See slapd-config(5) for details on configuration options.
# This file should NOT be world readable.
#
dn: cn=config
objectClass: olcGlobal
cn: config
#
#
# Define global ACLs to disable default read access.
#
olcArgsFile: /var/run/openldap/slapd.args
olcPidFile: /var/run/openldap/slapd.pid
olcTLSCertificateFile: /usr/local/etc/openldap/server.crt <co xml:id="server-certificate"/>
olcTLSCertificateKeyFile: /usr/local/etc/openldap/private/server.key <co xml:id="server-key"/>
olcTLSCACertificateFile: /usr/local/etc/openldap/ca.crt <co xml:id="ca"/>
#olcTLSCipherSuite: HIGH:MEDIUM:+SSLv3 <co xml:id="cipher-suite"/>
olcTLSProtocolMin: 3.1 <co xml:id="protocol-min"/>
olcTLSVerifyClient: never <co xml:id="verify-client"/></programlisting>
<calloutlist>
<callout arearefs="server-certificate">
<para>Specifies the location of the server certificate
for TLS operations.</para>
</callout>
<callout arearefs="server-key">
<para>Specifies the location of the server key.</para>
</callout>
<callout arearefs="ca">
<para>Specifies the location of the Certificate
Authority.</para>
</callout>
<callout arearefs="cipher-suite">
<para>An option <literal>olcTLSCipherSuite</literal> can
be specified, but here is commented; it was suggested
to have the value <literal>HIGH:MEDIUM:+SSLv3</literal>.
It should be noted in fact that <literal>SSLv3</literal>
has been deprecated by IETF and that the syntax
<literal>HIGH:MEDIUM</literal> is related to <filename>
openssl</filename>; when clients with different
Operating Systems try to connect to this server, they
may not be able to parse this value. In order to
connect to an <acronym>LDAP</acronym> server using TLS,
each client machine must run a <literal>TLS
client</literal>. Linux machines, for example, use
<filename>gnutls</filename> as <literal>TLS
client</literal> instead of <filename>
openssl</filename>. An error is generated if the
option
<literal>olcTLSCipherSuite: HIGH:MEDIUM:+SSLv3</literal>
is used with the shown syntax.
Otherwise <emphasis>all the clients</emphasis> will not
run FreeBSD, it is recommended to omit such a line, and
let the client OS choose the security cipher: this way,
the server configuration can be done and acceptable,
regardless of the <literal>TLS client</literal>s that
will connect.
The security cipher will be chosen according to the
available ciphers in the client machine, hopefully being
the most secure at the present time: it is not advisable
that the server force it and this is another benefit
when omitting the <literal>olcTLSCipherSuite</literal>.
The security of the client ciphers is demanded to the
package maintainers of the TLS clients.</para>
</callout>
<callout arearefs="protocol-min">
<para>The <acronym>LDAP</acronym> server Administrator can
anyway specify a minimum security level required by the
server. Unlike for the previous one, the use of this
option is recommended:
<literal>olcTLSProtocolMin</literal>.</para>
</callout>
<callout arearefs="verify-client">
<para>Server must always be verified, while clients can be
verified or not: with <literal>
olcTLSVerifyClient</literal>, in this example the
clients are not verified.</para>
</callout>
</calloutlist>
<para>The second part is about the backend modules and can be
configured as follows:</para>
<programlisting>#
# Load dynamic backend modules:
#
dn: cn=module,cn=config
objectClass: olcModuleList
cn: module
olcModulepath: /usr/local/libexec/openldap
olcModuleload: back_mdb.la
#olcModuleload: back_bdb.la
#olcModuleload: back_hdb.la
#olcModuleload: back_ldap.la
#olcModuleload: back_passwd.la
#olcModuleload: back_shell.la</programlisting>
<para>The third part is devoted to load the needed <literal>
ldif</literal> schemas to be used by the databases: they
are essential.</para>
<programlisting>dn: cn=schema,cn=config
objectClass: olcSchemaConfig
cn: schema
include: file:///usr/local/etc/openldap/schema/core.ldif
include: file:///usr/local/etc/openldap/schema/cosine.ldif
include: file:///usr/local/etc/openldap/schema/inetorgperson.ldif
include: file:///usr/local/etc/openldap/schema/nis.ldif</programlisting>
<para>Then, the frontend configuration follows:</para>
<programlisting># Frontend settings
#
dn: olcDatabase={-1}frontend,cn=config
objectClass: olcDatabaseConfig
objectClass: olcFrontendConfig
olcDatabase: {-1}frontend
olcAccess: to * by * read
#
# Sample global access control policy:
# Root DSE: allow anyone to read it
# Subschema (sub)entry DSE: allow anyone to read it
# Other DSEs:
# Allow self write access
# Allow authenticated users read access
# Allow anonymous users to authenticate
#
#olcAccess: to dn.base="" by * read
#olcAccess: to dn.base="cn=Subschema" by * read
#olcAccess: to *
# by self write
# by users read
# by anonymous auth
#
# if no access controls are present, the default policy
# allows anyone and everyone to read anything but restricts
# updates to rootdn. (e.g., "access to * by * read")
#
# rootdn can always read and write EVERYTHING!
#
olcPasswordHash: {SSHA}
# {SSHA} is already the default for olcPasswordHash</programlisting>
<para>The following section describes the configuration
backend: this will be the <emphasis>only way</emphasis> to
access the global configuration for the system
administrator, once this procedure is completed. Thus, it
is <emphasis>extremely important</emphasis> that all the
needed options are specified here. In particular, a root
password must be chosen: together with the default
administrator username <literal>cn=config</literal>, it will
let the server administrator to later edit the configuration
as the super-user. Note that, without the specification of
a <literal>olcRootPW</literal> here, after this file is
imported as a configuration file for <filename>
slapd</filename>, no one will be able to modify this
global configuration. This is highly undesirable.
If anyway something is wrong with the actual configuration,
later will be shown a way to delete (and hopefully replace)
it.
A password can be generated using <filename>
slappasswd</filename> in a shell and its entire output must
be used as a value for <literal>olcRootPW</literal>.</para>
<programlisting>dn: olcDatabase={0}config,cn=config
objectClass: olcDatabaseConfig
olcDatabase: {0}config
olcAccess: to * by * none
olcRootPW: {SSHA}iae+lrQZILpiUdf16Z9KmDmSwT77Dj4U</programlisting>
<para>The last section showed here is about the database
backend, used for the <emphasis>actual contents</emphasis>
of the <acronym>LDAP</acronym> directory. This database can
be used to add new groups and users as regards the domain
<literal>domain.example</literal>. Here, the database type
<literal>mdb</literal> is used and another super-user is
specified: it will be only able to modify this database and
not the previous sections of <filename>
slapd.ldif</filename>. Here, a username <literal>
olcRootDN</literal> can be specified, being related to the
domain. A password can be generated as before.</para>
<programlisting>#######################################################################
# LMDB database definitions
#######################################################################
#
dn: olcDatabase=mdb,cn=config
objectClass: olcDatabaseConfig
objectClass: olcMdbConfig
olcDatabase: mdb
olcDbMaxSize: 1073741824
olcSuffix: dc=domain,dc=example
olcRootDN: cn=mdbadmin,dc=domain,dc=example
# Cleartext passwords, especially for the rootdn, should
# be avoided. See slappasswd(8) and slapd-config(5) for details.
# Use of strong authentication encouraged.
olcRootPW: {SSHA}X2wHvIWDk6G76CQyCMS1vDCvtICWgn0+
# The database directory MUST exist prior to running slapd AND
# should only be accessible by the slapd and slap tools.
# Mode 700 recommended.
olcDbDirectory: /var/db/openldap-data
# Indices to maintain
olcDbIndex: objectClass eq</programlisting>
<para>In <link xlink:href=
"http://www.openldap.org/devel/gitweb.cgi?p=openldap.git;a=tree;f=tests/data/regressions/its8444;h=8a5e808e63b0de3d2bdaf2cf34fecca8577ca7fd;hb=HEAD">
this repository</link>, four examples of <filename>
slapd.ldif</filename> files are available (they are used
as a 4-way multi master <acronym>LDAP</acronym> server). At
the bottom of <link
xlink:href="http://www.openldap.org/doc/admin24/slapdconf2.html">
this page</link>, section 5.4, also a way to convert an
existing <filename>slapd.conf</filename> into a valid
<filename>slapd.ldif</filename> is presented. Please note
that this may introduce some unuseful options.</para>
<para>Once the <filename>slapd.ldif</filename> configuration
is completed, this file must be imported in an empty
directory. It is recommended to create it with the
following name and location:</para>
<screen>&prompt.root; <userinput>mkdir /usr/local/etc/openldap/slapd.d/</userinput></screen>
<para>The commands suggested at points 9 and 10 in the <link
xlink:href="http://www.openldap.org/doc/admin24/quickstart.html">
OpenLDAP Quick Start guide</link> (which can anyway be
considered as a reference for all the other operations) are
currently wrong: instead, it is advisable to use</para>
<screen>&prompt.root; <userinput>/usr/local/sbin/slapadd -n0 -F /usr/local/etc/openldap/slapd.d/ -l /usr/local/etc/openldap/slapd.ldif</userinput></screen>
<para>This will import the configuration database. To start
the slapd daemon,</para>
<screen>&prompt.root; <userinput>/usr/local/libexec/slapd -F /usr/local/etc/openldap/slapd.d/</userinput></screen>
<para>Option <literal>-d</literal> can be used for debugging,
as specified in <link xlink:href=
"https://www.freebsd.org/cgi/man.cgi?query=slapd&amp;sektion=8&amp;manpath=FreeBSD+11.0-RELEASE+and+Ports">
slapd(8)</link>. To verify that the server is running and
working,</para>
<screen>&prompt.root; <userinput>ldapsearch -x -b '' -s base '(objectclass=*)' namingContexts</userinput>
# extended LDIF
#
# LDAPv3
# base &lt;&gt; with scope baseObject
# filter: (objectclass=*)
# requesting: namingContexts
#
#
dn:
namingContexts: dc=domain,dc=example
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1</screen>
<para>The server will not still be recognized by any client as
trusted, anyway.
The certificates were created in non-standard directories
from the point of view of <filename>openssl</filename>. In
order for <filename>openssl</filename> to work, the
directories where the certificates are stored must contain
symbolic links (whose names are composed by a hash) to the
certificates. Even if some <filename>openssl</filename>
commands are already available in a FreeBSD base system, it
is necessary now to explicitly install the package:</para>
<screen>&prompt.root; <userinput>pkg install openssl</userinput></screen>
<para>This will provide the <link xlink:href=
"https://www.freebsd.org/cgi/man.cgi?query=c_rehash&amp;manpath=FreeBSD+11.0-RELEASE+and+Ports">c_rehash(1)</link>
tool. Now run</para>
<screen>&prompt.root; <userinput>c_rehash .</userinput></screen>
<para>from the directory where the CA is stored (in this
example, <filename>/usr/local/etc/openldap</filename>,
which contains the file <filename>ca.crt</filename>). This
utility must create a symlink for each
<filename>.pem</filename>, <filename>.crt</filename>,
<filename>.crl</filename> or <filename>.cer</filename> file
in the directory. Only this way <filename>
server.crt</filename> can be recognized as a valid, trusted
and acceptable certificate. After having verified that
symlinks have been created, in order to verify if the server
certificate is trusted (and this is the operation each
<acronym>LDAP</acronym> client does before accessing the
server), run (from the <filename>server.crt</filename>
directory):</para>
<screen>&prompt.root; <userinput>openssl verify -verbose -CApath . server.crt</userinput></screen>
<para>If <filename>slapd</filename> was running, it must now
be restarted before using the server.
Please, carefully read the comments included in
<filename>/usr/local/etc/rc.d/slapd</filename>, to make a
correct configuration to run <filename>slapd</filename> at
boot.
An additional option is needed if the
<literal>cn=config</literal> style (that is: the file
<filename>slapd.ldif</filename>) is used for configuration.
You could put in <filename>/etc/rc.conf</filename> the
following lines:</para>
<programlisting>lapd_enable="YES"
slapd_flags='-h "ldapi://%2fvar%2frun%2fopenldap%2fldapi/
ldap://0.0.0.0/"'
slapd_sockets="/var/run/openldap/ldapi"
slapd_cn_config="YES"</programlisting>
<para><filename>slapd</filename> does not provide debugging at
boot, but <filename>dmesg -a</filename>, <filename>
/var/log/messages</filename> and (in particular)
<filename>/var/log/debug.log</filename> can be checked.</para>
<para>The <acronym>LDAP</acronym> users database is still
empty. An example, which adds a group called
<literal>team</literal> and a user called
<literal>john</literal> to the
<systemitem class="systemname">domain.example</systemitem>
database is here provided. Create a file <filename>
domain.ldif</filename> with the following contents:</para>
<screen>&prompt.root; <userinput>cat domain.ldif</userinput>
dn: dc=domain,dc=example
objectClass: dcObject
objectClass: organization
o: domain.example
dc: domain
dn: ou=groups,dc=domain,dc=example
objectClass: top
objectClass: organizationalunit
ou: groups
dn: ou=users,dc=domain,dc=example
objectClass: top
objectClass: organizationalunit
ou: users
dn: cn=team,ou=groups,dc=domain,dc=example
objectClass: top
objectClass: posixGroup
cn: team
gidNumber: 10001
dn: uid=john,ou=users,dc=domain,dc=example
objectClass: top
objectClass: account
objectClass: posixAccount
objectClass: shadowAccount
cn: John McUser
uid: john
uidNumber: 10001
gidNumber: 10001
homeDirectory: /home/john/
loginShell: /usr/bin/bash
userPassword: secret</screen>
<para>Instead of being <literal>secret</literal>, the password
in the last line of <filename>domain.ldif</filename> for
<literal>john</literal> can be generated with
<filename>slappasswd</filename>. Be careful about the
default shell path:
if it does not exist in the system where the user tries to log
in, an error can be generated and the user could not be able
to actually log in. A symlink can be created, or a different
shell can be used to avoid this. For the structure of the
<literal>ldif</literal> files and the <acronym>LDAP</acronym>
directory, see the OpenLDAP documentation. Such data can be
added to the database using the <literal>mdb</literal>
administrator:</para>
<screen>&prompt.root; <userinput>ldapadd -W -D "cn=mdbadmin,dc=domain,dc=example" -f domain.ldif</userinput></screen>
<para>If instead a global option is to be modified, a
<emphasis>different user</emphasis> must be considered: as
anticipated, it is the <emphasis>global</emphasis>
super-user. Let us assume that the option
<literal>olcTLSCipherSuite: HIGH:MEDIUM:SSLv3</literal> was
specified before and now it must be deleted. The
instructions for the modification can be stored in the file
<filename>global_mod</filename>.
It must not contain the previous value of the option to be
deleted in the last line: this means that
<literal>olcTLSCipherSuite: HIGH:MEDIUM:SSLv3</literal> must
not be included as last line.</para>
<screen>&prompt.root; <userinput>cat global_mod</userinput>
dn: cn=config
changetype: modify
delete: olcTLSCipherSuite</screen>
<para>The modifications can be applied with</para>
<screen>&prompt.root; <userinput>ldapmodify -f global_mod -x -D "cn=config" -W</userinput></screen>
<para><literal>cn=config</literal> is the
<literal>dn</literal> (Distinguished Name) of the entry
(section) of the database to be modified.
Use <literal>ldapmodify</literal> to delete a single line
of the database; <literal>ldapdelete</literal> is used to
delete an entire entry (section) instead.
Each database section has its own administrator and it must
be specified while applying a modification.
The global super-user, whose name is by default
<literal>cn=config</literal>, should have a password set by
<literal>olcRootPW</literal> in the
<literal>dn: olcDatabase={0}config,cn=config</literal>
section. It is the one who must used here. If something
goes wrong, or if this root administrator cannot access the
configuration backend, it is possible to completeley delete
the current configuration. It can be done by removing the
directory that was previously created:</para>
<screen>&prompt.root; <userinput>rm -rf /usr/local/etc/openldap/slapd.d/</userinput></screen>
<para><filename>slapd.ldif</filename> can then be edited and
imported again. Please note that this procedure
is not to be considered as ordinary, nor normal:
it will not have side effects, but it should be followed
<emphasis>only</emphasis> when no other solution is
suitable.</para>
<para>This is the configuration of the server only. The
client, which can be the server itself, and/or another
machine, relies upon other configuration files: a dedicated
guide must be followed for them.</para>
</sect2>
</sect1>
<sect1 xml:id="network-dhcp">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Greg</firstname>
<surname>Sutter</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect1info>
-->
<title>Dynamic Host Configuration Protocol
(<acronym>DHCP</acronym>)</title>
<indexterm>
<primary>Dynamic Host Configuration Protocol</primary>
<see><acronym>DHCP</acronym></see>
</indexterm>
<indexterm>
<primary>Internet Systems Consortium (ISC)</primary>
</indexterm>
<para>The Dynamic Host Configuration Protocol
(<acronym>DHCP</acronym>) allows a system to connect to a
network in order to be assigned the necessary addressing
information for communication on that network. &os; includes
the OpenBSD version of <command>dhclient</command> which is used
by the client to obtain the addressing information. &os; does
not install a <acronym>DHCP</acronym> server, but several
servers are available in the &os; Ports Collection. The
<acronym>DHCP</acronym> protocol is fully described in <link
xlink:href="http://www.freesoft.org/CIE/RFC/2131/">RFC
2131</link>.
Informational resources are also available at <link
xlink:href="http://www.isc.org/downloads/dhcp/">isc.org/downloads/dhcp/</link>.</para>
<para>This section describes how to use the built-in
<acronym>DHCP</acronym> client. It then describes how to
install and configure a <acronym>DHCP</acronym> server.</para>
<note>
<para>In &os;, the &man.bpf.4; device is needed by both the
<acronym>DHCP</acronym> server and <acronym>DHCP</acronym>
client. This device is included in the
<filename>GENERIC</filename> kernel that is installed with
&os;. Users who prefer to create a custom kernel need to keep
this device if <acronym>DHCP</acronym> is used.</para>
<para>It should be noted that <filename>bpf</filename> also
allows privileged users to run network packet sniffers on
that system.</para>
</note>
<sect2>
<title>Configuring a <acronym>DHCP</acronym> Client</title>
<para><acronym>DHCP</acronym> client support is included in the
&os; installer, making it easy to configure a newly installed
system to automatically receive its networking addressing
information from an existing <acronym>DHCP</acronym> server.
Refer to <xref linkend="bsdinstall-post"/> for examples of
network configuration.</para>
<indexterm><primary><acronym>UDP</acronym></primary></indexterm>
<para>When <command>dhclient</command> is executed on the client
machine, it begins broadcasting requests for configuration
information. By default, these requests use
<acronym>UDP</acronym> port 68. The server replies on
<acronym>UDP</acronym> port 67, giving the client an
<acronym>IP</acronym> address and other relevant network
information such as a subnet mask, default gateway, and
<acronym>DNS</acronym> server addresses. This information is
in the form of a <acronym>DHCP</acronym>
<quote>lease</quote> and is valid for a configurable time.
This allows stale <acronym>IP</acronym> addresses for clients
no longer connected to the network to automatically be reused.
<acronym>DHCP</acronym> clients can obtain a great deal of
information from the server. An exhaustive list may be found
in &man.dhcp-options.5;.</para>
<para>By default, when a &os; system boots, its
<acronym>DHCP</acronym> client runs in the background, or
<firstterm>asynchronously</firstterm>. Other startup scripts
continue to run while the <acronym>DHCP</acronym> process
completes, which speeds up system startup.</para>
<para>Background <acronym>DHCP</acronym> works well when the
<acronym>DHCP</acronym> server responds quickly to the
client's requests. However, <acronym>DHCP</acronym> may take
a long time to complete on some systems. If network services
attempt to run before <acronym>DHCP</acronym> has assigned the
network addressing information, they will fail. Using
<acronym>DHCP</acronym> in <firstterm>synchronous</firstterm>
mode prevents this problem as it pauses startup until the
<acronym>DHCP</acronym> configuration has completed.</para>
<para>This line in <filename>/etc/rc.conf</filename> is used to
configure background or asynchronous mode:</para>
<programlisting>ifconfig_<replaceable>fxp0</replaceable>="DHCP"</programlisting>
<para>This line may already exist if the system was configured
to use <acronym>DHCP</acronym> during installation. Replace
the <replaceable>fxp0</replaceable> shown in these examples
with the name of the interface to be dynamically configured,
as described in <xref linkend="config-network-setup"/>.</para>
<para>To instead configure the system to use synchronous mode,
and to pause during startup while <acronym>DHCP</acronym>
completes, use
<quote><literal>SYNCDHCP</literal></quote>:</para>
<programlisting>ifconfig_<replaceable>fxp0</replaceable>="SYNCDHCP"</programlisting>
<para>Additional client options are available. Search for
<literal>dhclient</literal> in &man.rc.conf.5; for
details.</para>
<indexterm>
<primary><acronym>DHCP</acronym></primary>
<secondary>configuration files</secondary>
</indexterm>
<para>The <acronym>DHCP</acronym> client uses the following
files:</para>
<itemizedlist>
<listitem>
<para><filename>/etc/dhclient.conf</filename></para>
<para>The configuration file used by
<command>dhclient</command>. Typically, this file
contains only comments as the defaults are suitable for
most clients. This configuration file is described in
&man.dhclient.conf.5;.</para>
</listitem>
<listitem>
<para><filename>/sbin/dhclient</filename></para>
<para>More information about the command itself can
be found in &man.dhclient.8;.</para>
</listitem>
<listitem>
<para><filename>/sbin/dhclient-script</filename></para>
<para>The
&os;-specific <acronym>DHCP</acronym> client configuration
script. It is described in &man.dhclient-script.8;, but
should not need any user modification to function
properly.</para>
</listitem>
<listitem>
<para><filename>/var/db/dhclient.leases.<replaceable>interface</replaceable></filename></para>
<para>The <acronym>DHCP</acronym> client keeps a database of
valid leases in this file, which is written as a log and
is described in &man.dhclient.leases.5;.</para>
</listitem>
</itemizedlist>
</sect2>
<sect2 xml:id="network-dhcp-server">
<title>Installing and Configuring a <acronym>DHCP</acronym>
Server</title>
<para>This section demonstrates how to configure a &os; system
to act as a <acronym>DHCP</acronym> server using the Internet
Systems Consortium (<acronym>ISC</acronym>) implementation of
the <acronym>DHCP</acronym> server. This implementation and
its documentation can be installed using the
<package>net/isc-dhcp43-server</package> package or
port.</para>
<indexterm>
<primary><acronym>DHCP</acronym></primary>
<secondary>server</secondary>
</indexterm>
<indexterm>
<primary><acronym>DHCP</acronym></primary>
<secondary>installation</secondary>
</indexterm>
<para>The installation of
<package>net/isc-dhcp43-server</package> installs a sample
configuration file. Copy
<filename>/usr/local/etc/dhcpd.conf.example</filename> to
<filename>/usr/local/etc/dhcpd.conf</filename> and make any
edits to this new file.</para>
<indexterm>
<primary><acronym>DHCP</acronym></primary>
<secondary>dhcpd.conf</secondary>
</indexterm>
<para>The configuration file is comprised of declarations for
subnets and hosts which define the information that is
provided to <acronym>DHCP</acronym> clients. For example,
these lines configure the following:</para>
<programlisting>option domain-name "example.org";<co xml:id="domain-name"/>
option domain-name-servers ns1.example.org;<co xml:id="domain-name-servers"/>
option subnet-mask 255.255.255.0;<co xml:id="subnet-mask"/>
default-lease-time 600;<co xml:id="default-lease-time"/>
max-lease-time 72400;<co xml:id="max-lease-time"/>
ddns-update-style none;<co xml:id="ddns-update-style"/>
subnet 10.254.239.0 netmask 255.255.255.224 {
range 10.254.239.10 10.254.239.20;<co xml:id="range"/>
option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;<co xml:id="routers"/>
}
host fantasia {
hardware ethernet 08:00:07:26:c0:a5;<co xml:id="hardware"/>
fixed-address fantasia.fugue.com;<co xml:id="fixed-address"/>
}</programlisting>
<calloutlist>
<callout arearefs="domain-name">
<para>This option specifies the default search domain that
will be provided to clients. Refer to
&man.resolv.conf.5; for more information.</para>
</callout>
<callout arearefs="domain-name-servers">
<para>This option specifies a comma separated list of
<acronym>DNS</acronym> servers that the client should use.
They can be listed by their Fully Qualified Domain Names
(<acronym>FQDN</acronym>), as seen in the example, or by
their <acronym>IP</acronym> addresses.</para>
</callout>
<callout arearefs="subnet-mask">
<para>The subnet mask that will be provided to
clients.</para>
</callout>
<callout arearefs="default-lease-time">
<para>The default lease expiry time in seconds. A client
can be configured to override this value. </para>
</callout>
<callout arearefs="max-lease-time">
<para>The maximum allowed length of time, in seconds, for a
lease. Should a client request a longer lease, a lease
will still be issued, but it will only be valid for
<literal>max-lease-time</literal>.</para>
</callout>
<callout arearefs="ddns-update-style">
<para>The default of <option>none</option> disables dynamic
DNS updates. Changing this to <option>interim</option>
configures the <acronym>DHCP</acronym> server to update a
<acronym>DNS</acronym> server whenever it hands out a
lease so that the <acronym>DNS</acronym> server knows
which <acronym>IP</acronym> addresses are associated with
which computers in the network. Do not change the default
setting unless the <acronym>DNS</acronym> server has been
configured to support dynamic
<acronym>DNS</acronym>.</para>
</callout>
<callout arearefs="range">
<para>This line creates a pool of available
<acronym>IP</acronym> addresses which are reserved for
allocation to <acronym>DHCP</acronym> clients. The range
of addresses must be valid for the network or subnet
specified in the previous line.</para>
</callout>
<callout arearefs="routers">
<para>Declares the default gateway that is valid for the
network or subnet specified before the opening
<literal>{</literal> bracket.</para>
</callout>
<callout arearefs="hardware">
<para>Specifies the hardware <acronym>MAC</acronym> address
of a client so that the <acronym>DHCP</acronym> server can
recognize the client when it makes a request.</para>
</callout>
<callout arearefs="fixed-address">
<para>Specifies that this host should always be given the
same <acronym>IP</acronym> address. Using the hostname is
correct, since the <acronym>DHCP</acronym> server will
resolve the hostname before returning the lease
information.</para>
</callout>
</calloutlist>
<para>This configuration file supports many more options. Refer
to dhcpd.conf(5), installed with the server, for details and
examples.</para>
<para>Once the configuration of <filename>dhcpd.conf</filename>
is complete, enable the <acronym>DHCP</acronym> server in
<filename>/etc/rc.conf</filename>:</para>
<programlisting>dhcpd_enable="YES"
dhcpd_ifaces="dc0"</programlisting>
<para>Replace the <literal>dc0</literal> with the interface (or
interfaces, separated by whitespace) that the
<acronym>DHCP</acronym> server should listen on for
<acronym>DHCP</acronym> client requests.</para>
<para>Start the server by issuing the following command:</para>
<screen>&prompt.root; <userinput>service isc-dhcpd start</userinput></screen>
<para>Any future changes to the configuration of the server will
require the <application>dhcpd</application> service to be
stopped and then started using &man.service.8;.</para>
<para>The <acronym>DHCP</acronym> server uses the following
files. Note that the manual pages are installed with the
server software.</para>
<indexterm>
<primary><acronym>DHCP</acronym></primary>
<secondary>configuration files</secondary>
</indexterm>
<itemizedlist>
<listitem>
<para><filename>/usr/local/sbin/dhcpd</filename></para>
<para>More information about the
<application>dhcpd</application> server can be found in
dhcpd(8).</para>
</listitem>
<listitem>
<para><filename>/usr/local/etc/dhcpd.conf</filename></para>
<para>The server configuration file needs to contain all the
information that should be provided to clients, along with
information regarding the operation of the server. This
configuration file is described in dhcpd.conf(5).</para>
</listitem>
<listitem>
<para><filename>/var/db/dhcpd.leases</filename></para>
<para>The <acronym>DHCP</acronym> server keeps a database of
leases it has issued in this file, which is written as a
log. Refer to dhcpd.leases(5), which gives a slightly
longer description.</para>
</listitem>
<listitem>
<para><filename>/usr/local/sbin/dhcrelay</filename></para>
<para>This daemon is used in advanced environments where one
<acronym>DHCP</acronym> server forwards a request from a
client to another <acronym>DHCP</acronym> server on a
separate network. If this functionality is required,
install the <package>net/isc-dhcp43-relay</package>
package or port. The installation includes dhcrelay(8)
which provides more detail.</para>
</listitem>
</itemizedlist>
</sect2>
</sect1>
<sect1 xml:id="network-dns">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Chern</firstname>
<surname>Lee</surname>
<contrib>Contributed by </contrib>
</author>
<author>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
</author>
<author>
<firstname>Daniel</firstname>
<surname>Gerzo</surname>
</author>
</authorgroup>
</sect1info>
-->
<title>Domain Name System (<acronym>DNS</acronym>)</title>
<indexterm><primary>DNS</primary></indexterm>
<para>Domain Name System (<acronym>DNS</acronym>) is the protocol
through which domain names are mapped to <acronym>IP</acronym>
addresses, and vice versa. <acronym>DNS</acronym> is
coordinated across the Internet through a somewhat complex
system of authoritative root, Top Level Domain
(<acronym>TLD</acronym>), and other smaller-scale name servers,
which host and cache individual domain information. It is not
necessary to run a name server to perform
<acronym>DNS</acronym> lookups on a system.</para>
<indexterm><primary>BIND</primary></indexterm>
<para>In &os; 10, the Berkeley Internet Name Domain
(<acronym>BIND</acronym>) has been removed from the base system
and replaced with Unbound. Unbound as configured in the &os;
Base is a local caching resolver. <acronym>BIND</acronym> is
still available from The Ports Collection as <package
role="port">dns/bind99</package> or <package
role="port">dns/bind98</package>. In &os; 9 and lower,
<acronym>BIND</acronym> is included in &os; Base. The &os;
version provides enhanced security features, a new file system
layout, and automated &man.chroot.8; configuration.
<acronym>BIND</acronym> is maintained by the <link
xlink:href="https://www.isc.org/">Internet Systems
Consortium</link>.</para>
<indexterm><primary>resolver</primary></indexterm>
<indexterm><primary>reverse
<acronym>DNS</acronym></primary></indexterm>
<indexterm><primary>root zone</primary></indexterm>
<para>The following table describes some of the terms associated
with <acronym>DNS</acronym>:</para>
<table frame="none" pgwide="1">
<title><acronym>DNS</acronym> Terminology</title>
<tgroup cols="2">
<colspec colwidth="1*"/>
<colspec colwidth="3*"/>
<thead>
<row>
<entry>Term</entry>
<entry>Definition</entry>
</row>
</thead>
<tbody>
<row>
<entry>Forward <acronym>DNS</acronym></entry>
<entry>Mapping of hostnames to <acronym>IP</acronym>
addresses.</entry>
</row>
<row>
<entry>Origin</entry>
<entry>Refers to the domain covered in a particular zone
file.</entry>
</row>
<row>
<entry><application>named</application>, BIND</entry>
<entry>Common names for the BIND name server package
within &os;.</entry>
</row>
<row>
<entry>Resolver</entry>
<entry>A system process through which a machine queries
a name server for zone information.</entry>
</row>
<row>
<entry>Reverse <acronym>DNS</acronym></entry>
<entry>Mapping of <acronym>IP</acronym> addresses to
hostnames.</entry>
</row>
<row>
<entry>Root zone</entry>
<entry>The beginning of the Internet zone hierarchy. All
zones fall under the root zone, similar to how all files
in a file system fall under the root directory.</entry>
</row>
<row>
<entry>Zone</entry>
<entry>An individual domain, subdomain, or portion of the
<acronym>DNS</acronym> administered by the same
authority.</entry>
</row>
</tbody>
</tgroup>
</table>
<indexterm>
<primary>zones</primary>
<secondary>examples</secondary>
</indexterm>
<para>Examples of zones:</para>
<itemizedlist>
<listitem>
<para><systemitem>.</systemitem> is how the root zone is
usually referred to in documentation.</para>
</listitem>
<listitem>
<para><systemitem>org.</systemitem> is a Top Level Domain
(<acronym>TLD</acronym>) under the root zone.</para>
</listitem>
<listitem>
<para><systemitem
class="fqdomainname">example.org.</systemitem> is a zone
under the <systemitem>org.</systemitem>
<acronym>TLD</acronym>.</para>
</listitem>
<listitem>
<para><systemitem>1.168.192.in-addr.arpa</systemitem> is a
zone referencing all <acronym>IP</acronym> addresses which
fall under the <systemitem
class="ipaddress">192.168.1.*</systemitem>
<acronym>IP</acronym> address space.</para>
</listitem>
</itemizedlist>
<para>As one can see, the more specific part of a hostname
appears to its left. For example, <systemitem
class="fqdomainname">example.org.</systemitem> is more
specific than <systemitem>org.</systemitem>, as
<systemitem>org.</systemitem> is more specific than the root
zone. The layout of each part of a hostname is much like a file
system: the <filename>/dev</filename> directory falls within the
root, and so on.</para>
<sect2>
<title>Reasons to Run a Name Server</title>
<para>Name servers generally come in two forms: authoritative
name servers, and caching (also known as resolving) name
servers.</para>
<para>An authoritative name server is needed when:</para>
<itemizedlist>
<listitem>
<para>One wants to serve <acronym>DNS</acronym> information
to the world, replying authoritatively to queries.</para>
</listitem>
<listitem>
<para>A domain, such as <systemitem
class="fqdomainname">example.org</systemitem>, is
registered and <acronym>IP</acronym> addresses need to be
assigned to hostnames under it.</para>
</listitem>
<listitem>
<para>An <acronym>IP</acronym> address block requires
reverse <acronym>DNS</acronym> entries
(<acronym>IP</acronym> to hostname).</para>
</listitem>
<listitem>
<para>A backup or second name server, called a slave, will
reply to queries.</para>
</listitem>
</itemizedlist>
<para>A caching name server is needed when:</para>
<itemizedlist>
<listitem>
<para>A local <acronym>DNS</acronym> server may cache and
respond more quickly than querying an outside name
server.</para>
</listitem>
</itemizedlist>
<para>When one queries for <systemitem
class="fqdomainname">www.FreeBSD.org</systemitem>, the
resolver usually queries the uplink <acronym>ISP</acronym>'s
name server, and retrieves the reply. With a local, caching
<acronym>DNS</acronym> server, the query only has to be made
once to the outside world by the caching
<acronym>DNS</acronym> server. Additional queries will not
have to go outside the local network, since the information is
cached locally.</para>
</sect2>
<sect2>
<title><acronym>DNS</acronym> Server Configuration in &os; 10.0
and Later</title>
<para>In &os; 10.0, <application>BIND</application> has been
replaced with <application>Unbound</application>.
<application>Unbound</application> is a validating caching
resolver only. If an authoritative server is needed, many are
available from the Ports Collection.</para>
<para><application>Unbound</application> is provided in the &os;
base system. By default, it will provide
<acronym>DNS</acronym> resolution to the local machine only.
While the base system package can be configured to provide
resolution services beyond the local machine, it is
recommended that such requirements be addressed by installing
<application>Unbound</application> from the &os; Ports
Collection.</para>
<para>To enable <application>Unbound</application>, add the
following to <filename>/etc/rc.conf</filename>:</para>
<programlisting>local_unbound_enable="YES"</programlisting>
<para>Any existing nameservers in
<filename>/etc/resolv.conf</filename> will be configured as
forwarders in the new <application>Unbound</application>
configuration.</para>
<note>
<para>If any of the listed nameservers do not support
<acronym>DNSSEC</acronym>, local <acronym>DNS</acronym>
resolution will fail. Be sure to test each nameserver and
remove any that fail the test. The following command will
show the trust tree or a failure for a nameserver running on
<systemitem
class="ipaddress">192.168.1.1</systemitem>:</para>
</note>
<screen>&prompt.user; <userinput>drill -S FreeBSD.org @<replaceable>192.168.1.1</replaceable></userinput></screen>
<para>Once each nameserver is confirmed to support
<acronym>DNSSEC</acronym>, start
<application>Unbound</application>:</para>
<screen>&prompt.root; <userinput>service local_unbound onestart</userinput></screen>
<para>This will take care of updating
<filename>/etc/resolv.conf</filename> so that queries for
<acronym>DNSSEC</acronym> secured domains will now work. For
example, run the following to validate the FreeBSD.org
<acronym>DNSSEC</acronym> trust tree:</para>
<screen>&prompt.user; <userinput>drill -S FreeBSD.org</userinput>
;; Number of trusted keys: 1
;; Chasing: freebsd.org. A
DNSSEC Trust tree:
freebsd.org. (A)
|---freebsd.org. (DNSKEY keytag: 36786 alg: 8 flags: 256)
|---freebsd.org. (DNSKEY keytag: 32659 alg: 8 flags: 257)
|---freebsd.org. (DS keytag: 32659 digest type: 2)
|---org. (DNSKEY keytag: 49587 alg: 7 flags: 256)
|---org. (DNSKEY keytag: 9795 alg: 7 flags: 257)
|---org. (DNSKEY keytag: 21366 alg: 7 flags: 257)
|---org. (DS keytag: 21366 digest type: 1)
| |---. (DNSKEY keytag: 40926 alg: 8 flags: 256)
| |---. (DNSKEY keytag: 19036 alg: 8 flags: 257)
|---org. (DS keytag: 21366 digest type: 2)
|---. (DNSKEY keytag: 40926 alg: 8 flags: 256)
|---. (DNSKEY keytag: 19036 alg: 8 flags: 257)
;; Chase successful</screen>
</sect2>
<sect2>
<title>DNS Server Configuration in &os;
9.<replaceable>X</replaceable></title>
<para>In &os;, the BIND daemon is called
<application>named</application>.</para>
<informaltable frame="none" pgwide="1">
<tgroup cols="2">
<thead>
<row>
<entry>File</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>&man.named.8;</entry>
<entry>The BIND daemon.</entry>
</row>
<row>
<entry>&man.rndc.8;</entry>
<entry>Name server control utility.</entry>
</row>
<row>
<entry><filename>/etc/namedb</filename></entry>
<entry>Directory where BIND zone information
resides.</entry>
</row>
<row>
<entry><filename>/etc/namedb/named.conf</filename></entry>
<entry>Configuration file of the daemon.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>Depending on how a given zone is configured on the server,
the files related to that zone can be found in the
<filename>master</filename>,
<filename>slave</filename>, or
<filename>dynamic</filename> subdirectories
of the <filename>/etc/namedb</filename>
directory. These files contain the <acronym>DNS</acronym>
information that will be given out by the name server in
response to queries.</para>
<sect3>
<title>Starting BIND</title>
<indexterm>
<primary>BIND</primary>
<secondary>starting</secondary>
</indexterm>
<para>Since BIND is installed by default, configuring it is
relatively simple.</para>
<para>The default <application>named</application>
configuration is that of a basic resolving name server,
running in a &man.chroot.8; environment, and restricted to
listening on the local IPv4 loopback address (127.0.0.1).
To start the server one time with this configuration, use
the following command:</para>
<screen>&prompt.root; <userinput>service named onestart</userinput></screen>
<para>To ensure the <application>named</application> daemon is
started at boot each time, put the following line into the
<filename>/etc/rc.conf</filename>:</para>
<programlisting>named_enable="YES"</programlisting>
<para>There are many configuration options for
<filename>/etc/namedb/named.conf</filename> that are beyond
the scope of this document. Other startup options for
<application>named</application> on &os; can be found in the
<literal>named_<replaceable>*</replaceable></literal> flags
in <filename>/etc/defaults/rc.conf</filename> and in
&man.rc.conf.5;. The <xref linkend="configtuning-rcd"/>
section is also a good read.</para>
</sect3>
<sect3>
<title>Configuration Files</title>
<indexterm>
<primary>BIND</primary>
<secondary>configuration files</secondary>
</indexterm>
<para>Configuration files for <application>named</application>
currently reside in <filename>/etc/namedb</filename>
directory and will need modification before use unless all
that is needed is a simple resolver. This is where most of
the configuration will be performed.</para>
<sect4>
<title><filename>/etc/namedb/named.conf</filename></title>
<programlisting>// <phrase its:translate="no">&dollar;FreeBSD&dollar;</phrase>
//
// Refer to the named.conf(5) and named(8) man pages, and the documentation
// in /usr/share/doc/bind9 for more details.
//
// If you are going to set up an authoritative server, make sure you
// understand the hairy details of how DNS works. Even with
// simple mistakes, you can break connectivity for affected parties,
// or cause huge amounts of useless Internet traffic.
options {
// All file and path names are relative to the chroot directory,
// if any, and should be fully qualified.
directory "/etc/namedb/working";
pid-file "/var/run/named/pid";
dump-file "/var/dump/named_dump.db";
statistics-file "/var/stats/named.stats";
// If named is being used only as a local resolver, this is a safe default.
// For named to be accessible to the network, comment this option, specify
// the proper IP address, or delete this option.
listen-on { 127.0.0.1; };
// If you have IPv6 enabled on this system, uncomment this option for
// use as a local resolver. To give access to the network, specify
// an IPv6 address, or the keyword "any".
// listen-on-v6 { ::1; };
// These zones are already covered by the empty zones listed below.
// If you remove the related empty zones below, comment these lines out.
disable-empty-zone "255.255.255.255.IN-ADDR.ARPA";
disable-empty-zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
disable-empty-zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
// If you have a DNS server around at your upstream provider, enter
// its IP address here, and enable the line below. This will make you
// benefit from its cache, thus reduce overall DNS traffic in the Internet.
/*
forwarders {
127.0.0.1;
};
*/
// If the 'forwarders' clause is not empty the default is to 'forward first'
// which will fall back to sending a query from your local server if the name
// servers in 'forwarders' do not have the answer. Alternatively you can
// force your name server to never initiate queries of its own by enabling the
// following line:
// forward only;
// If you wish to have forwarding configured automatically based on
// the entries in /etc/resolv.conf, uncomment the following line and
// set named_auto_forward=yes in /etc/rc.conf. You can also enable
// named_auto_forward_only (the effect of which is described above).
// include "/etc/namedb/auto_forward.conf";</programlisting>
<para>Just as the comment says, to benefit from an uplink's
cache, <literal>forwarders</literal> can be enabled here.
Under normal circumstances, a name server will recursively
query the Internet looking at certain name servers until
it finds the answer it is looking for. Having this
enabled will have it query the uplink's name server (or
name server provided) first, taking advantage of its
cache. If the uplink name server in question is a heavily
trafficked, fast name server, enabling this may be
worthwhile.</para>
<warning>
<para><systemitem class="ipaddress">127.0.0.1</systemitem>
will <emphasis>not</emphasis> work here. Change this
<acronym>IP</acronym> address to a name server at the
uplink.</para>
</warning>
<programlisting> /*
Modern versions of BIND use a random <acronym>UDP</acronym> port for each outgoing
query by default in order to dramatically reduce the possibility
of cache poisoning. All users are strongly encouraged to utilize
this feature, and to configure their firewalls to accommodate it.
AS A LAST RESORT in order to get around a restrictive firewall
policy you can try enabling the option below. Use of this option
will significantly reduce your ability to withstand cache poisoning
attacks, and should be avoided if at all possible.
Replace NNNNN in the example with a number between 49160 and 65530.
*/
// query-source address * port NNNNN;
};
// If you enable a local name server, do not forget to enter 127.0.0.1
// first in your /etc/resolv.conf so this server will be queried.
// Also, make sure to enable it in /etc/rc.conf.
// The traditional root hints mechanism. Use this, OR the slave zones below.
zone "." { type hint; file "/etc/namedb/named.root"; };
/* Slaving the following zones from the root name servers has some
significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
3. Greater resilience to any potential root server failure/DDoS
On the other hand, this method requires more monitoring than the
hints file to be sure that an unexpected failure mode has not
incapacitated your server. Name servers that are serving a lot
of clients will benefit more from this approach than individual
hosts. Use with caution.
To use this mechanism, uncomment the entries below, and comment
the hint zone above.
As documented at http://dns.icann.org/services/axfr/ these zones:
"." (the root), ARPA, IN-ADDR.ARPA, IP6.ARPA, and ROOT-SERVERS.NET
are available for AXFR from these servers on IPv4 and IPv6:
xfr.lax.dns.icann.org, xfr.cjr.dns.icann.org
*/
/*
zone "." {
type slave;
file "/etc/namedb/slave/root.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
zone "arpa" {
type slave;
file "/etc/namedb/slave/arpa.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
*/
/* Serving the following zones locally will prevent any queries
for these zones leaving your network and going to the root
name servers. This has two significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
*/
// RFCs 1912 and 5735 (and BCP 32 for localhost)
zone "localhost" { type master; file "/etc/namedb/master/localhost-forward.db"; };
zone "127.in-addr.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
zone "255.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// RFC 1912-style zone for IPv6 localhost address
zone "0.ip6.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
// "This" Network (RFCs 1912 and 5735)
zone "0.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Private Use Networks (RFCs 1918 and 5735)
zone "10.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "16.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "17.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "18.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "20.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "21.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "22.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "23.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "24.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "25.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "26.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "27.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "28.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "29.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "30.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "31.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "168.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Link-local/APIPA (RFCs 3927 and 5735)
zone "254.169.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IETF protocol assignments (RFCs 5735 and 5736)
zone "0.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// TEST-NET-[1-3] for Documentation (RFCs 5735 and 5737)
zone "2.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "100.51.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "113.0.203.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Range for Documentation (RFC 3849)
zone "8.b.d.0.1.0.0.2.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Domain Names for Documentation and Testing (BCP 32)
zone "test" { type master; file "/etc/namedb/master/empty.db"; };
zone "example" { type master; file "/etc/namedb/master/empty.db"; };
zone "invalid" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.com" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.net" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.org" { type master; file "/etc/namedb/master/empty.db"; };
// Router Benchmark Testing (RFCs 2544 and 5735)
zone "18.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IANA Reserved - Old Class E Space (RFC 5735)
zone "240.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "241.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "242.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "243.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "244.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "245.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "246.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "247.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "248.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "249.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "250.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "251.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "252.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "253.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "254.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Unassigned Addresses (RFC 4291)
zone "1.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "c.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 ULA (RFC 4193)
zone "c.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Link Local (RFC 4291)
zone "8.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Deprecated Site-Local Addresses (RFC 3879)
zone "c.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "f.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IP6.INT is Deprecated (RFC 4159)
zone "ip6.int" { type master; file "/etc/namedb/master/empty.db"; };
// NB: Do not use the IP addresses below, they are faked, and only
// serve demonstration/documentation purposes!
//
// Example slave zone config entries. It can be convenient to become
// a slave at least for the zone your own domain is in. Ask
// your network administrator for the IP address of the responsible
// master name server.
//
// Do not forget to include the reverse lookup zone!
// This is named after the first bytes of the IP address, in reverse
// order, with ".IN-ADDR.ARPA" appended, or ".IP6.ARPA" for IPv6.
//
// Before starting to set up a master zone, make sure you fully
// understand how DNS and BIND work. There are sometimes
// non-obvious pitfalls. Setting up a slave zone is usually simpler.
//
// NB: Do not blindly enable the examples below. :-) Use actual names
// and addresses instead.
/* An example dynamic zone
key "exampleorgkey" {
algorithm hmac-md5;
secret "sf87HJqjkqh8ac87a02lla==";
};
zone "example.org" {
type master;
allow-update {
key "exampleorgkey";
};
file "/etc/namedb/dynamic/example.org";
};
*/
/* Example of a slave reverse zone
zone "1.168.192.in-addr.arpa" {
type slave;
file "/etc/namedb/slave/1.168.192.in-addr.arpa";
masters {
192.168.1.1;
};
};
*/</programlisting>
<para>In <filename>named.conf</filename>, these are examples
of slave entries for a forward and reverse zone.</para>
<para>For each new zone served, a new zone entry must be
added to <filename>named.conf</filename>.</para>
<para>For example, the simplest zone entry for
<systemitem class="fqdomainname">example.org</systemitem>
can look like:</para>
<programlisting>zone "example.org" {
type master;
file "master/example.org";
};</programlisting>
<para>The zone is a master, as indicated by the
<option>type</option> statement, holding its zone
information in
<filename>/etc/namedb/master/example.org</filename>
indicated by the <option>file</option> statement.</para>
<programlisting>zone "example.org" {
type slave;
file "slave/example.org";
};</programlisting>
<para>In the slave case, the zone information is transferred
from the master name server for the particular zone, and
saved in the file specified. If and when the master
server dies or is unreachable, the slave name server will
have the transferred zone information and will be able to
serve it.</para>
</sect4>
<sect4>
<title>Zone Files</title>
<indexterm>
<primary>BIND</primary>
<secondary>zone files</secondary>
</indexterm>
<para>An example master zone file for
<systemitem class="fqdomainname">example.org</systemitem>
(existing within
<filename>/etc/namedb/master/example.org</filename>) is as
follows:</para>
<programlisting>&dollar;TTL 3600 ; 1 hour default TTL
example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ; Negative Response TTL
)
; DNS Servers
IN NS ns1.example.org.
IN NS ns2.example.org.
; MX Records
IN MX 10 mx.example.org.
IN MX 20 mail.example.org.
IN A 192.168.1.1
; Machine Names
localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5
; Aliases
www IN CNAME example.org.</programlisting>
<para>Note that every hostname ending in a <quote>.</quote>
is an exact hostname, whereas everything without a
trailing <quote>.</quote> is relative to the origin. For
example, <literal>ns1</literal> is translated into
<literal>ns1.<replaceable>example.org.</replaceable></literal></para>
<para>The format of a zone file follows:</para>
<programlisting>recordname IN recordtype value</programlisting>
<indexterm>
<primary><acronym>DNS</acronym></primary>
<secondary>records</secondary>
</indexterm>
<para>The most commonly used <acronym>DNS</acronym>
records:</para>
<variablelist>
<varlistentry>
<term>SOA</term>
<listitem>
<para>start of zone authority</para>
</listitem>
</varlistentry>
<varlistentry>
<term>NS</term>
<listitem>
<para>an authoritative name server</para>
</listitem>
</varlistentry>
<varlistentry>
<term>A</term>
<listitem>
<para>a host address</para>
</listitem>
</varlistentry>
<varlistentry>
<term>CNAME</term>
<listitem>
<para>the canonical name for an alias</para>
</listitem>
</varlistentry>
<varlistentry>
<term>MX</term>
<listitem>
<para>mail exchanger</para>
</listitem>
</varlistentry>
<varlistentry>
<term>PTR</term>
<listitem>
<para>a domain name pointer (used in reverse
<acronym>DNS</acronym>)</para>
</listitem>
</varlistentry>
</variablelist>
<programlisting>example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh after 3 hours
3600 ; Retry after 1 hour
604800 ; Expire after 1 week
300 ) ; Negative Response TTL</programlisting>
<variablelist>
<varlistentry>
<term><systemitem
class="fqdomainname">example.org.</systemitem></term>
<listitem>
<para>the domain name, also the origin for this
zone file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><systemitem
class="fqdomainname">ns1.example.org.</systemitem></term>
<listitem>
<para>the primary/authoritative name server for this
zone.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>admin.example.org.</literal></term>
<listitem>
<para>the responsible person for this zone,
email address with <quote>@</quote>
replaced. (<email>admin@example.org</email> becomes
<literal>admin.example.org</literal>)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>2006051501</literal></term>
<listitem>
<para>the serial number of the file. This must be
incremented each time the zone file is modified.
Nowadays, many admins prefer a
<literal>yyyymmddrr</literal> format for the serial
number. <literal>2006051501</literal> would mean
last modified 05/15/2006, the latter
<literal>01</literal> being the first time the zone
file has been modified this day. The serial number
is important as it alerts slave name servers for a
zone when it is updated.</para>
</listitem>
</varlistentry>
</variablelist>
<programlisting> IN NS ns1.example.org.</programlisting>
<para>This is an NS entry. Every name server that is going
to reply authoritatively for the zone must have one of
these entries.</para>
<programlisting>localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5</programlisting>
<para>The A record indicates machine names. As seen above,
<systemitem
class="fqdomainname">ns1.example.org</systemitem> would
resolve to <systemitem
class="ipaddress">192.168.1.2</systemitem>.</para>
<programlisting> IN A 192.168.1.1</programlisting>
<para>This line assigns <acronym>IP</acronym> address
<systemitem class="ipaddress">192.168.1.1</systemitem> to
the current origin, in this case <systemitem
class="fqdomainname">example.org</systemitem>.</para>
<programlisting>www IN CNAME @</programlisting>
<para>The canonical name record is usually used for giving
aliases to a machine. In the example,
<systemitem>www</systemitem> is aliased to the
<quote>master</quote> machine whose name happens to be the
same as the domain name
<systemitem class="fqdomainname">example.org</systemitem>
(<systemitem class="ipaddress">192.168.1.1</systemitem>).
CNAMEs can never be used together with another kind of
record for the same hostname.</para>
<indexterm>
<primary>MX record</primary>
</indexterm>
<programlisting> IN MX 10 mail.example.org.</programlisting>
<para>The MX record indicates which mail servers are
responsible for handling incoming mail for the zone.
<systemitem
class="fqdomainname">mail.example.org</systemitem> is
the hostname of a mail server, and 10 is the priority of
that mail server.</para>
<para>One can have several mail servers, with priorities of
10, 20 and so on. A mail server attempting to deliver to
<systemitem class="fqdomainname">example.org</systemitem>
would first try the highest priority MX (the record with
the lowest priority number), then the second highest, etc,
until the mail can be properly delivered.</para>
<para>For in-addr.arpa zone files (reverse
<acronym>DNS</acronym>), the same format is used, except
with PTR entries instead of A or CNAME.</para>
<programlisting>$TTL 3600
1.168.192.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ) ; Negative Response TTL
IN NS ns1.example.org.
IN NS ns2.example.org.
1 IN PTR example.org.
2 IN PTR ns1.example.org.
3 IN PTR ns2.example.org.
4 IN PTR mx.example.org.
5 IN PTR mail.example.org.</programlisting>
<para>This file gives the proper <acronym>IP</acronym>
address to hostname mappings for the above fictitious
domain.</para>
<para>It is worth noting that all names on the right side
of a PTR record need to be fully qualified (i.e., end in
a <quote>.</quote>).</para>
</sect4>
</sect3>
<sect3>
<title>Caching Name Server</title>
<indexterm>
<primary>BIND</primary>
<secondary>caching name server</secondary>
</indexterm>
<para>A caching name server is a name server whose primary
role is to resolve recursive queries. It simply asks
queries of its own, and remembers the answers for later
use.</para>
</sect3>
<sect3>
<title><acronym role="Domain Name Security
Extensions">DNSSEC</acronym></title>
<indexterm>
<primary>BIND</primary>
<secondary><acronym>DNS</acronym> security
extensions</secondary>
</indexterm>
<para>Domain Name System Security Extensions, or <acronym
role="Domain Name Security Extensions">DNSSEC</acronym>
for short, is a suite of specifications to protect resolving
name servers from forged <acronym>DNS</acronym> data, such
as spoofed <acronym>DNS</acronym> records. By using digital
signatures, a resolver can verify the integrity of the
record. Note that <acronym role="Domain Name Security
Extensions">DNSSEC</acronym> only provides integrity via
digitally signing the Resource Records (<acronym
role="Resource Record">RR</acronym>s). It provides
neither confidentiality nor protection against false
end-user assumptions. This means that it cannot protect
against people going to
<systemitem class="fqdomainname">example.net</systemitem>
instead of
<systemitem class="fqdomainname">example.com</systemitem>.
The only thing <acronym>DNSSEC</acronym> does is
authenticate that the data has not been compromised in
transit. The security of <acronym>DNS</acronym> is an
important step in securing the Internet in general. For
more in-depth details of how <acronym>DNSSEC</acronym>
works, the relevant <acronym>RFC</acronym>s are a good place
to start. See the list in
<xref linkend="dns-read"/>.</para>
<para>The following sections will demonstrate how to enable
<acronym>DNSSEC</acronym> for an authoritative
<acronym>DNS</acronym> server and a recursive (or caching)
<acronym>DNS</acronym> server running
<acronym>BIND</acronym> 9. While all versions of
<acronym>BIND</acronym> 9 support <acronym>DNSSEC</acronym>,
it is necessary to have at least version 9.6.2 in order to
be able to use the signed root zone when validating
<acronym>DNS</acronym> queries. This is because earlier
versions lack the required algorithms to enable validation
using the root zone key. It is strongly recommended to use
the latest version of <acronym>BIND</acronym> 9.7 or later
to take advantage of automatic key updating for the root
key, as well as other features to automatically keep zones
signed and signatures up to date. Where configurations
differ between 9.6.2 and 9.7 and later, differences will be
pointed out.</para>
<sect4>
<title>Recursive <acronym>DNS</acronym> Server
Configuration</title>
<para>Enabling <acronym>DNSSEC</acronym> validation of
queries performed by a recursive <acronym>DNS</acronym>
server requires a few changes to
<filename>named.conf</filename>. Before making these
changes the root zone key, or trust anchor, must be
acquired. Currently the root zone key is not available in
a file format <acronym>BIND</acronym> understands, so it
has to be manually converted into the proper format. The
key itself can be obtained by querying the root zone for
it using <application>dig</application>. By
running</para>
<screen>&prompt.user; <userinput>dig +multi +noall +answer DNSKEY . &gt; root.dnskey</userinput></screen>
<para>the key will end up in
<filename>root.dnskey</filename>. The contents should
look something like this:</para>
<programlisting>. 93910 IN DNSKEY 257 3 8 (
AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQ
bSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh
/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWA
JQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXp
oY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3
LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGO
Yl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGc
LmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=
) ; key id = 19036
. 93910 IN DNSKEY 256 3 8 (
AwEAAcaGQEA+OJmOzfzVfoYN249JId7gx+OZMbxy69Hf
UyuGBbRN0+HuTOpBxxBCkNOL+EJB9qJxt+0FEY6ZUVjE
g58sRr4ZQ6Iu6b1xTBKgc193zUARk4mmQ/PPGxn7Cn5V
EGJ/1h6dNaiXuRHwR+7oWh7DnzkIJChcTqlFrXDW3tjt
) ; key id = 34525</programlisting>
<para>Do not be alarmed if the obtained keys differ from
this example. They might have changed since these
instructions were last updated. This output actually
contains two keys. The first key in the listing, with the
value 257 after the DNSKEY record type, is the one needed.
This value indicates that this is a Secure Entry Point
(<acronym role="Secure Entry Point">SEP</acronym>),
commonly known as a Key Signing Key
(<acronym role="Key Signing Key">KSK</acronym>). The
second key, with value 256, is a subordinate key, commonly
called a Zone Signing Key
(<acronym role="Zone Signing Key">ZSK</acronym>). More on
the different key types later in
<xref linkend="dns-dnssec-auth"/>.</para>
<para>Now the key must be verified and formatted so that
<acronym>BIND</acronym> can use it. To verify the key,
generate a <acronym role="Delegation Signer">DS</acronym>
<acronym role="Resource Record">RR</acronym> set. Create
a file containing these
<acronym role="Resource Record">RR</acronym>s with</para>
<screen>&prompt.user; <userinput>dnssec-dsfromkey -f root.dnskey . &gt; root.ds</userinput></screen>
<para>These records use SHA-1 and SHA-256 respectively, and
should look similar to the following example, where the
longer is using SHA-256.</para>
<programlisting>. IN DS 19036 8 1
B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E
. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5</programlisting>
<para>The SHA-256 <acronym>RR</acronym> can now be compared
to the digest in <link
xlink:href="https://data.iana.org/root-anchors/root-anchors.xml">https://data.iana.org/root-anchors/root-anchors.xml</link>.
To be absolutely sure that the key has not been tampered
with the data in the <acronym>XML</acronym> file should be
verified using a proper <acronym>PGP</acronym> signature.</para>
<para>Next, the key must be formatted properly. This
differs a little between <acronym>BIND</acronym> versions
9.6.2 and 9.7 and later. In version 9.7 support was added
to automatically track changes to the key and update it as
necessary. This is done using
<literal>managed-keys</literal> as seen in the example
below. When using the older version, the key is added
using a <literal>trusted-keys</literal> statement and
updates must be done manually. For
<acronym>BIND</acronym> 9.6.2 the format should look
like:</para>
<programlisting>trusted-keys {
"." 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};</programlisting>
<para>For 9.7 the format will instead be:</para>
<programlisting>managed-keys {
"." initial-key 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};</programlisting>
<para>The root key can now be added to
<filename>named.conf</filename> either directly or by
including a file containing the key. After these steps,
configure <acronym>BIND</acronym> to do
<acronym>DNSSEC</acronym> validation on queries by editing
<filename>named.conf</filename> and adding the following
to the <literal>options</literal> directive:</para>
<programlisting>dnssec-enable yes;
dnssec-validation yes;</programlisting>
<para>To verify that it is actually working use
<application>dig</application> to make a query for a
signed zone using the resolver just configured. A
successful reply will contain the <literal>AD</literal>
flag to indicate the data was authenticated. Running a
query such as</para>
<screen>&prompt.user; <userinput>dig @<replaceable>resolver</replaceable> +dnssec se ds </userinput></screen>
<para>should return the <acronym>DS</acronym>
<acronym>RR</acronym> for the <literal>.se</literal> zone.
In the <literal>flags:</literal> section the
<literal>AD</literal> flag should be set, as seen
in:</para>
<programlisting>...
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
...</programlisting>
<para>The resolver is now capable of authenticating
<acronym>DNS</acronym> queries.</para>
</sect4>
<sect4 xml:id="dns-dnssec-auth">
<title>Authoritative <acronym>DNS</acronym> Server
Configuration</title>
<para>In order to get an authoritative name server to serve
a <acronym>DNSSEC</acronym> signed zone a little more work
is required. A zone is signed using cryptographic keys
which must be generated. It is possible to use only one
key for this. The preferred method however is to have a
strong well-protected Key Signing Key
(<acronym role="Key Signing Key">KSK</acronym>) that is
not rotated very often and a Zone Signing Key
(<acronym role="Zone Signing Key">ZSK</acronym>) that is
rotated more frequently. Information on recommended
operational practices can be found in <link
xlink:href="http://tools.ietf.org/rfc/rfc4641.txt"><acronym>RFC</acronym>
4641: <acronym>DNSSEC</acronym> Operational
Practices</link>. Practices regarding the root zone can
be found in <link
xlink:href="http://www.root-dnssec.org/wp-content/uploads/2010/06/icann-dps-00.txt"><acronym>DNSSEC</acronym>
Practice Statement for the Root Zone
<acronym>KSK</acronym> operator</link> and <link
xlink:href="http://www.root-dnssec.org/wp-content/uploads/2010/06/vrsn-dps-00.txt"><acronym>DNSSEC</acronym>
Practice Statement for the Root Zone
<acronym>ZSK</acronym> operator</link>. The
<acronym role="Key Signing Key">KSK</acronym> is used to
build a chain of authority to the data in need of
validation and as such is also called a Secure Entry Point
(<acronym role="Secure Entry Point">SEP</acronym>) key. A
message digest of this key, called a Delegation Signer
(<acronym role="Delegation Signer">DS</acronym>) record,
must be published in the parent zone to establish the
trust chain. How this is accomplished depends on the
parent zone owner. The
<acronym role="Zone Signing Key">ZSK</acronym> is used to
sign the zone, and only needs to be published
there.</para>
<para>To enable <acronym>DNSSEC</acronym> for the
<systemitem class="fqdomainname">example.com</systemitem>
zone depicted in previous examples, the first step is to
use <application>dnssec-keygen</application> to generate
the <acronym>KSK</acronym> and <acronym>ZSK</acronym> key
pair. This key pair can utilize different cryptographic
algorithms. It is recommended to use RSA/SHA256 for the
keys and 2048 bits key length should be enough. To
generate the <acronym>KSK</acronym> for
<systemitem class="fqdomainname">example.com</systemitem>,
run</para>
<screen>&prompt.user; <userinput>dnssec-keygen -f KSK -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
<para>and to generate the <acronym>ZSK</acronym>, run</para>
<screen>&prompt.user; <userinput>dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
<para><application>dnssec-keygen</application> outputs two
files, the public and the private keys in files named
similar to
<filename>Kexample.com.+005+nnnnn.key</filename> (public)
and <filename>Kexample.com.+005+nnnnn.private</filename>
(private). The <literal>nnnnn</literal> part of the file
name is a five digit key ID. Keep track of which key ID
belongs to which key. This is especially important when
having more than one key in a zone. It is also possible
to rename the keys. For each <acronym>KSK</acronym> file
do:</para>
<screen>&prompt.user; <userinput>mv Kexample.com.+005+nnnnn.key Kexample.com.+005+nnnnn.KSK.key</userinput>
&prompt.user; <userinput>mv Kexample.com.+005+nnnnn.private Kexample.com.+005+nnnnn.KSK.private</userinput></screen>
<para>For the <acronym>ZSK</acronym> files, substitute
<literal>KSK</literal> for <literal>ZSK</literal> as
necessary. The files can now be included in the zone
file, using the <literal>$include</literal> statement. It
should look something like this:</para>
<programlisting>$include Kexample.com.+005+nnnnn.KSK.key ; KSK
$include Kexample.com.+005+nnnnn.ZSK.key ; ZSK</programlisting>
<para>Finally, sign the zone and tell
<acronym>BIND</acronym> to use the signed zone file. To
sign a zone <application>dnssec-signzone</application> is
used. The command to sign the zone
<systemitem class="fqdomainname">example.com</systemitem>,
located in <filename>example.com.db</filename> would look
similar to</para>
<screen>&prompt.user; <userinput>dnssec-signzone -o example.com -k Kexample.com.+005+nnnnn.KSK example.com.db Kexample.com.+005+nnnnn.ZSK.key</userinput></screen>
<para>The key supplied to the <option>-k</option> argument
is the <acronym>KSK</acronym> and the other key file is
the <acronym>ZSK</acronym> that should be used in the
signing. It is possible to supply more than one
<acronym>KSK</acronym> and <acronym>ZSK</acronym>, which
will result in the zone being signed with all supplied
keys. This can be needed to supply zone data signed using
more than one algorithm. The output of
<application>dnssec-signzone</application> is a zone file
with all <acronym>RR</acronym>s signed. This output will
end up in a file with the extension
<literal>.signed</literal>, such as
<filename>example.com.db.signed</filename>. The
<acronym role="Delegation Signer">DS</acronym> records
will also be written to a separate file
<filename>dsset-example.com</filename>. To use this
signed zone just modify the zone directive in
<filename>named.conf</filename> to use
<filename>example.com.db.signed</filename>. By default,
the signatures are only valid 30 days, meaning that the
zone needs to be resigned in about 15 days to be sure
that resolvers are not caching records with stale
signatures. It is possible to make a script and a cron
job to do this. See relevant manuals for details.</para>
<para>Be sure to keep private keys confidential, as with all
cryptographic keys. When changing a key it is best to
include the new key into the zone, while still signing
with the old one, and then move over to using the new key
to sign. After these steps are done the old key can be
removed from the zone. Failure to do this might render
the <acronym>DNS</acronym> data unavailable for a time,
until the new key has propagated through the
<acronym>DNS</acronym> hierarchy. For more information on
key rollovers and other <acronym>DNSSEC</acronym>
operational issues, see <link
xlink:href="http://www.ietf.org/rfc/rfc4641.txt"><acronym>RFC</acronym>
4641: <acronym>DNSSEC</acronym> Operational
practices</link>.</para>
</sect4>
<sect4>
<title>Automation Using <acronym>BIND</acronym> 9.7 or
Later</title>
<para>Beginning with <acronym>BIND</acronym> version 9.7 a
new feature called <emphasis>Smart Signing</emphasis> was
introduced. This feature aims to make the key management
and signing process simpler by automating parts of the
task. By putting the keys into a directory called a
<emphasis>key repository</emphasis>, and using the new
option <literal>auto-dnssec</literal>, it is possible to
create a dynamic zone which will be resigned as needed.
To update this zone use
<application>nsupdate</application> with the new option
<option>-l</option>. <application>rndc</application> has
also grown the ability to sign zones with keys in the key
repository, using the option <option>sign</option>. To
tell <acronym>BIND</acronym> to use this automatic signing
and zone updating for <systemitem
class="fqdomainname">example.com</systemitem>, add the
following to <filename>named.conf</filename>:</para>
<programlisting>zone example.com {
type master;
key-directory "/etc/named/keys";
update-policy local;
auto-dnssec maintain;
file "/etc/named/dynamic/example.com.zone";
};</programlisting>
<para>After making these changes, generate keys for the zone
as explained in <xref linkend="dns-dnssec-auth"/>, put
those keys in the key repository given as the argument to
the <literal>key-directory</literal> in the zone
configuration and the zone will be signed automatically.
Updates to a zone configured this way must be done using
<application>nsupdate</application>, which will take care
of re-signing the zone with the new data added. For
further details, see <xref linkend="dns-read"/> and the
<acronym>BIND</acronym> documentation.</para>
</sect4>
</sect3>
<sect3>
<title>Security</title>
<para>Although BIND is the most common implementation of
<acronym>DNS</acronym>, there is always the issue of
security. Possible and exploitable security holes are
sometimes found.</para>
<para>While &os; automatically drops
<application>named</application> into a &man.chroot.8;
environment; there are several other security mechanisms in
place which could help to lure off possible
<acronym>DNS</acronym> service attacks.</para>
<para>It is always good idea to read
<link xlink:href="http://www.cert.org/">CERT</link>'s
security advisories and to subscribe to the
&a.security-notifications; to stay up to date with the
current Internet and &os; security issues.</para>
<tip>
<para>If a problem arises, keeping sources up to date and
having a fresh build of <application>named</application>
may help.</para>
</tip>
</sect3>
<sect3 xml:id="dns-read">
<title>Further Reading</title>
<para>BIND/<application>named</application> manual pages:
&man.rndc.8; &man.named.8; &man.named.conf.5;
&man.nsupdate.1; &man.dnssec-signzone.8;
&man.dnssec-keygen.8;</para>
<itemizedlist>
<listitem>
<para><link
xlink:href="https://www.isc.org/software/bind">Official
ISC BIND Page</link></para>
</listitem>
<listitem>
<para><link
xlink:href="https://www.isc.org/software/guild">Official
ISC BIND Forum</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://www.oreilly.com/catalog/dns5/">O'Reilly
<acronym>DNS</acronym> and BIND 5th
Edition</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://www.root-dnssec.org/documentation/">Root
<acronym>DNSSEC</acronym></link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://data.iana.org/root-anchors/draft-icann-dnssec-trust-anchor.html"><acronym>DNSSEC</acronym>
Trust Anchor Publication for the Root
Zone</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc1034">RFC1034
- Domain Names - Concepts and Facilities</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc1035">RFC1035
- Domain Names - Implementation and
Specification</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc4033">RFC4033
- <acronym>DNS</acronym> Security Introduction and
Requirements</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc4034">RFC4034
- Resource Records for the <acronym>DNS</acronym>
Security Extensions</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc4035">RFC4035
- Protocol Modifications for the
<acronym>DNS</acronym> Security
Extensions</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc4641">RFC4641
- DNSSEC Operational Practices</link></para>
</listitem>
<listitem>
<para><link
xlink:href="http://tools.ietf.org/html/rfc5011">RFC
5011 - Automated Updates of <acronym>DNS</acronym>
Security (<acronym>DNSSEC</acronym>
Trust Anchors</link></para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
</sect1>
<sect1 xml:id="network-apache">
<info>
<title>Apache HTTP Server</title>
<authorgroup>
<author>
<personname>
<firstname>Murray</firstname>
<surname>Stokely</surname>
</personname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</info>
<indexterm><primary>web servers</primary>
<secondary>setting up</secondary></indexterm>
<indexterm><primary>Apache</primary></indexterm>
<para>The open source
<application>Apache HTTP Server</application> is the most widely
used web server. &os; does not install this web server by
default, but it can be installed from the
<package>www/apache24</package> package or port.</para>
<para>This section summarizes how to configure and start version
2.<replaceable>x</replaceable> of the <application>Apache HTTP
Server</application> on &os;. For more detailed information
about <application>Apache</application>&nbsp;2.X and its
configuration directives, refer to <link
xlink:href="http://httpd.apache.org/">httpd.apache.org</link>.</para>
<sect2>
<title>Configuring and Starting Apache</title>
<indexterm><primary>Apache</primary>
<secondary>configuration file</secondary></indexterm>
<para>In &os;, the main <application>Apache HTTP
Server</application> configuration file is installed as
<filename>/usr/local/etc/apache2<replaceable>x</replaceable>/httpd.conf</filename>,
where <replaceable>x</replaceable> represents the version
number. This <acronym>ASCII</acronym> text file begins
comment lines with a <literal>#</literal>. The most
frequently modified directives are:</para>
<variablelist>
<varlistentry>
<term><literal>ServerRoot "/usr/local"</literal></term>
<listitem>
<para>Specifies the default directory hierarchy for the
<application>Apache</application> installation.
Binaries are stored in the <filename>bin</filename> and
<filename>sbin</filename> subdirectories of the server
root and configuration files are stored in the <filename
>etc/apache2<replaceable>x</replaceable></filename>
subdirectory.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ServerAdmin you@example.com</literal></term>
<listitem>
<para>Change this to the email address to receive problems
with the server. This address also appears on some
server-generated pages, such as error documents.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ServerName
www.example.com:80</literal></term>
<listitem>
<para>Allows an administrator to set a hostname which is
sent back to clients for the server. For example,
<systemitem>www</systemitem> can be used instead of the
actual hostname. If the system does not have a
registered <acronym>DNS</acronym> name, enter its
<acronym>IP</acronym> address instead. If the server
will listen on an alternate report, change
<literal>80</literal> to the alternate port
number.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DocumentRoot
"/usr/local/www/apache2<replaceable>x</replaceable>/data"</literal></term>
<listitem>
<para>The directory where documents will be served from.
By default, all requests are taken from this directory,
but symbolic links and aliases may be used to point to
other locations.</para>
</listitem>
</varlistentry>
</variablelist>
<para>It is always a good idea to make a backup copy of the
default <application>Apache</application> configuration file
before making changes. When the configuration of
<application>Apache</application> is complete, save the file
and verify the configuration using
<command>apachectl</command>. Running <command>apachectl
configtest</command> should return <literal>Syntax
OK</literal>.</para>
<indexterm><primary>Apache</primary>
<secondary>starting or stopping</secondary></indexterm>
<para>To launch <application>Apache</application> at system
startup, add the following line to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>apache<replaceable>24</replaceable>_enable="YES"</programlisting>
<para>If <application>Apache</application> should be started
with non-default options, the following line may be added to
<filename>/etc/rc.conf</filename> to specify the needed
flags:</para>
<programlisting>apache<replaceable>24</replaceable>_flags=""</programlisting>
<para>If <application>apachectl</application> does not report
configuration errors, start <command>httpd</command>
now:</para>
<screen>&prompt.root; <userinput>service apache<replaceable>24</replaceable> start</userinput></screen>
<para>The <command>httpd</command> service can be tested by
entering
<literal>http://<replaceable>localhost</replaceable></literal>
in a web browser, replacing
<replaceable>localhost</replaceable> with the fully-qualified
domain name of the machine running <command>httpd</command>.
The default web page that is displayed is
<filename>/usr/local/www/apache<replaceable>24</replaceable>/data/index.html</filename>.</para>
<para>The <application>Apache</application> configuration can be
tested for errors after making subsequent configuration
changes while <command>httpd</command> is running using the
following command:</para>
<screen>&prompt.root; <userinput>service apache<replaceable>24</replaceable> configtest</userinput></screen>
<note>
<para>It is important to note that
<literal>configtest</literal> is not an &man.rc.8; standard,
and should not be expected to work for all startup
scripts.</para>
</note>
</sect2>
<sect2>
<title>Virtual Hosting</title>
<para>Virtual hosting allows multiple websites to run on one
<application>Apache</application> server. The virtual hosts
can be <firstterm>IP-based</firstterm> or
<firstterm>name-based</firstterm>.
<acronym>IP</acronym>-based virtual hosting uses a different
<acronym>IP</acronym> address for each website. Name-based
virtual hosting uses the clients HTTP/1.1 headers to figure
out the hostname, which allows the websites to share the same
<acronym>IP</acronym> address.</para>
<para>To setup <application>Apache</application> to use
name-based virtual hosting, add a
<literal>VirtualHost</literal> block for each website. For
example, for the webserver named <systemitem
class="fqdomainname">www.domain.tld</systemitem> with a
virtual domain of <systemitem
class="fqdomainname">www.someotherdomain.tld</systemitem>,
add the following entries to
<filename>httpd.conf</filename>:</para>
<programlisting>&lt;VirtualHost *&gt;
ServerName <replaceable>www.domain.tld</replaceable>
DocumentRoot <replaceable>/www/domain.tld</replaceable>
&lt;/VirtualHost&gt;
&lt;VirtualHost *&gt;
ServerName <replaceable>www.someotherdomain.tld</replaceable>
DocumentRoot <replaceable>/www/someotherdomain.tld</replaceable>
&lt;/VirtualHost&gt;</programlisting>
<para>For each virtual host, replace the values for
<literal>ServerName</literal> and
<literal>DocumentRoot</literal> with the values to be
used.</para>
<para>For more information about setting up virtual hosts,
consult the official <application>Apache</application>
documentation at: <uri
xlink:href="http://httpd.apache.org/docs/vhosts/">http://httpd.apache.org/docs/vhosts/</uri>.</para>
</sect2>
<sect2>
<title>Apache Modules</title>
<indexterm><primary>Apache</primary>
<secondary>modules</secondary></indexterm>
<para><application>Apache</application> uses modules to augment
the functionality provided by the basic server. Refer to <uri
xlink:href="http://httpd.apache.org/docs/current/mod/">http://httpd.apache.org/docs/current/mod/</uri>
for a complete listing of and the configuration details for
the available modules.</para>
<para>In &os;, some modules can be compiled with the
<package>www/apache24</package> port. Type <command>make
config</command> within
<filename>/usr/ports/www/apache24</filename> to see which
modules are available and which are enabled by default. If
the module is not compiled with the port, the &os; Ports
Collection provides an easy way to install many modules. This
section describes three of the most commonly used
modules.</para>
<sect3>
<title><filename>mod_ssl</filename></title>
<indexterm>
<primary>web servers</primary>
<secondary>secure</secondary>
</indexterm>
<indexterm><primary>SSL</primary></indexterm>
<indexterm><primary>cryptography</primary></indexterm>
<para>The <filename>mod_ssl</filename> module uses the
<application>OpenSSL</application> library to provide strong
cryptography via the Secure Sockets Layer
(<acronym>SSLv3</acronym>) and Transport Layer Security
(<acronym>TLSv1</acronym>) protocols. This module provides
everything necessary to request a signed certificate from a
trusted certificate signing authority to run a secure web
server on &os;.</para>
<para>In &os;, <filename>mod_ssl</filename> module is enabled
by default in both the package and the port. The available
configuration directives are explained at <uri
xlink:href="http://httpd.apache.org/docs/current/mod/mod_ssl.html">http://httpd.apache.org/docs/current/mod/mod_ssl.html</uri>.</para>
</sect3>
<sect3>
<title><filename>mod_perl</filename></title>
<indexterm>
<primary>mod_perl</primary>
<secondary>Perl</secondary>
</indexterm>
<para>The
<filename>mod_perl</filename> module makes it possible to
write <application>Apache</application> modules in
<application>Perl</application>. In addition, the
persistent interpreter embedded in the server avoids the
overhead of starting an external interpreter and the penalty
of <application>Perl</application> start-up time.</para>
<para>The <filename>mod_perl</filename> can be installed using
the <package>www/mod_perl2</package> package or port.
Documentation for using this module can be found at <uri
xlink:href="http://perl.apache.org/docs/2.0/index.html">http://perl.apache.org/docs/2.0/index.html</uri>.</para>
</sect3>
<sect3>
<info>
<title><filename>mod_php</filename></title>
<authorgroup>
<author>
<personname>
<firstname>Tom</firstname>
<surname>Rhodes</surname>
</personname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</info>
<indexterm>
<primary>mod_php</primary>
<secondary>PHP</secondary>
</indexterm>
<para><firstterm>PHP: Hypertext Preprocessor</firstterm>
(<acronym>PHP</acronym>) is a general-purpose scripting
language that is especially suited for web development.
Capable of being embedded into <acronym>HTML</acronym>, its
syntax draws upon <application>C</application>, &java;, and
<application>Perl</application> with the intention of
allowing web developers to write dynamically generated
webpages quickly.</para>
<para>To gain support for <acronym>PHP</acronym>5 for the
<application>Apache</application> web server, install the
<package>www/mod_php56</package> package or port. This will
install and configure the modules required to support
dynamic <acronym>PHP</acronym> applications. The
installation will automatically add this line to
<filename>/usr/local/etc/apache2<replaceable>4</replaceable>/httpd.conf</filename>:</para>
<programlisting>LoadModule php5_module libexec/apache24/libphp5.so</programlisting>
<!--
I do not think this is still needed
AddModule mod_php5.c
&lt;IfModule mod_php5.c&gt;
DirectoryIndex index.php index.html
&lt;/IfModule&gt;
&lt;IfModule mod_php5.c&gt;
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
&lt;/IfModule&gt;</programlisting>
-->
<para>Then, perform a graceful restart to load the
<acronym>PHP</acronym> module:</para>
<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>
<para>The <acronym>PHP</acronym> support provided by
<package>www/mod_php56</package> is limited. Additional
support can be installed using the
<package>lang/php56-extensions</package> port which provides
a menu driven interface to the available
<acronym>PHP</acronym> extensions.</para>
<para>Alternatively, individual extensions can be installed
using the appropriate port. For instance, to add
<acronym>PHP</acronym> support for the
<application>MySQL</application> database server, install
<package>databases/php56-mysql</package>.</para>
<para>After installing an extension, the
<application>Apache</application> server must be reloaded to
pick up the new configuration changes:</para>
<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>
</sect3>
</sect2>
<sect2>
<title>Dynamic Websites</title>
<indexterm>
<primary>web servers</primary>
<secondary>dynamic</secondary>
</indexterm>
<para>In addition to <application>mod_perl</application> and
<application>mod_php</application>, other languages are
available for creating dynamic web content. These include
<application>Django</application> and
<application>Ruby on Rails</application>.</para>
<sect3>
<title>Django</title>
<indexterm><primary>Python</primary></indexterm>
<indexterm><primary>Django</primary></indexterm>
<para><application>Django</application> is a BSD-licensed
framework designed to allow developers to write high
performance, elegant web applications quickly. It provides
an object-relational mapper so that data types are developed
as <application>Python</application> objects. A rich
dynamic database-access <acronym>API</acronym> is provided
for those objects without the developer ever having to write
<acronym>SQL</acronym>. It also provides an extensible
template system so that the logic of the application is
separated from the <acronym>HTML</acronym>
presentation.</para>
<para>Django depends on <filename>mod_python</filename>, and
an <acronym>SQL</acronym> database engine. In &os;, the
<package>www/py-django</package> port automatically installs
<filename>mod_python</filename> and supports the
<application>PostgreSQL</application>,
<application>MySQL</application>, or
<application>SQLite</application> databases, with the
default being <application>SQLite</application>. To change
the database engine, type <command>make config</command>
within <filename>/usr/ports/www/py-django</filename>, then
install the port.</para>
<para>Once <application>Django</application> is installed, the
application will need a project directory along with the
<application>Apache</application> configuration in order to
use the embedded <application>Python</application>
interpreter. This interpreter is used to call the
application for specific <acronym>URL</acronym>s on the
site.</para>
<para>To configure <application>Apache</application> to pass
requests for certain <acronym>URL</acronym>s to the web
application, add the following to
<filename>httpd.conf</filename>, specifying the full path to
the project directory:</para>
<programlisting>&lt;Location "/"&gt;
SetHandler python-program
PythonPath "['<replaceable>/dir/to/the/django/packages/</replaceable>'] + sys.path"
PythonHandler django.core.handlers.modpython
SetEnv DJANGO_SETTINGS_MODULE mysite.settings
PythonAutoReload On
PythonDebug On
&lt;/Location&gt;</programlisting>
<para>Refer to <uri
xlink:href="https://docs.djangoproject.com">https://docs.djangoproject.com</uri>
for more information on how to use
<application>Django</application>.</para>
</sect3>
<sect3>
<title>Ruby on Rails</title>
<indexterm><primary>Ruby on Rails</primary></indexterm>
<para><application>Ruby on Rails</application> is another open
source web framework that provides a full development stack.
It is optimized to make web developers more productive and
capable of writing powerful applications quickly. On &os;,
it can be installed using the
<package>www/rubygem-rails</package> package or port.</para>
<para>Refer to <uri
xlink:href="http://guides.rubyonrails.org">http://guides.rubyonrails.org</uri>
for more information on how to use <application>Ruby on
Rails</application>.</para>
</sect3>
</sect2>
</sect1>
<sect1 xml:id="network-ftp">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
-->
<title>File Transfer Protocol (<acronym>FTP</acronym>)</title>
<indexterm><primary><acronym>FTP</acronym>
servers</primary></indexterm>
<para>The File Transfer Protocol (<acronym>FTP</acronym>) provides
users with a simple way to transfer files to and from an
<acronym>FTP</acronym> server. &os; includes
<acronym>FTP</acronym> server software,
<application>ftpd</application>, in the base system.</para>
<para>&os; provides several configuration files for controlling
access to the <acronym>FTP</acronym> server. This section
summarizes these files. Refer to &man.ftpd.8; for more details
about the built-in <acronym>FTP</acronym> server.</para>
<sect2>
<title>Configuration</title>
<para>The most important configuration step is deciding which
accounts will be allowed access to the <acronym>FTP</acronym>
server. A &os; system has a number of system accounts which
should not be allowed <acronym>FTP</acronym> access. The list
of users disallowed any <acronym>FTP</acronym> access can be
found in <filename>/etc/ftpusers</filename>. By default, it
includes system accounts. Additional users that should not be
allowed access to <acronym>FTP</acronym> can be added.</para>
<para>In some cases it may be desirable to restrict the access
of some users without preventing them completely from using
<acronym>FTP</acronym>. This can be accomplished be creating
<filename>/etc/ftpchroot</filename> as described in
&man.ftpchroot.5;. This file lists users and groups subject
to <acronym>FTP</acronym> access restrictions.</para>
<indexterm>
<primary><acronym>FTP</acronym></primary>
<secondary>anonymous</secondary>
</indexterm>
<para>To enable anonymous <acronym>FTP</acronym> access to the
server, create a user named <systemitem
class="username">ftp</systemitem> on the &os; system. Users
will then be able to log on to the
<acronym>FTP</acronym> server with a username of
<systemitem class="username">ftp</systemitem> or <systemitem
class="username">anonymous</systemitem>. When prompted for
the password, any input will be accepted, but by convention,
an email address should be used as the password. The
<acronym>FTP</acronym> server will call &man.chroot.2; when an
anonymous user logs in, to restrict access to only the home
directory of the <systemitem
class="username">ftp</systemitem> user.</para>
<para>There are two text files that can be created to specify
welcome messages to be displayed to <acronym>FTP</acronym>
clients. The contents of
<filename>/etc/ftpwelcome</filename> will be displayed to
users before they reach the login prompt. After a successful
login, the contents of
<filename>/etc/ftpmotd</filename> will be displayed. Note
that the path to this file is relative to the login
environment, so the contents of
<filename>~ftp/etc/ftpmotd</filename> would be displayed for
anonymous users.</para>
<para>Once the <acronym>FTP</acronym> server has been
configured, set the appropriate variable in
<filename>/etc/rc.conf</filename> to start the service during
boot:</para>
<programlisting>ftpd_enable="YES"</programlisting>
<para>To start the service now:</para>
<screen>&prompt.root; <userinput>service ftpd start</userinput></screen>
<para>Test the connection to the <acronym>FTP</acronym> server
by typing:</para>
<screen>&prompt.user; <userinput>ftp localhost</userinput></screen>
<indexterm><primary>syslog</primary></indexterm>
<indexterm><primary>log files</primary>
<secondary><acronym>FTP</acronym></secondary></indexterm>
<para>The <application>ftpd</application> daemon uses
&man.syslog.3; to log messages. By default, the system log
daemon will write messages related to <acronym>FTP</acronym>
in <filename>/var/log/xferlog</filename>. The location of
the <acronym>FTP</acronym> log can be modified by changing the
following line in
<filename>/etc/syslog.conf</filename>:</para>
<programlisting>ftp.info /var/log/xferlog</programlisting>
<indexterm>
<primary><acronym>FTP</acronym></primary>
<secondary>anonymous</secondary>
</indexterm>
<note>
<para>Be aware of the potential problems involved with running
an anonymous <acronym>FTP</acronym> server. In particular,
think twice about allowing anonymous users to upload files.
It may turn out that the <acronym>FTP</acronym> site becomes
a forum for the trade of unlicensed commercial software or
worse. If anonymous <acronym>FTP</acronym> uploads are
required, then verify the permissions so that these files
cannot be read by other anonymous users until they have
been reviewed by an administrator.</para>
</note>
</sect2>
</sect1>
<sect1 xml:id="network-samba">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Murray</firstname>
<surname>Stokely</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
-->
<title>File and Print Services for &microsoft.windows; Clients
(Samba)</title>
<indexterm><primary>Samba server</primary></indexterm>
<indexterm><primary>Microsoft Windows</primary></indexterm>
<indexterm>
<primary>file server</primary>
<secondary>Windows clients</secondary>
</indexterm>
<indexterm>
<primary>print server</primary>
<secondary>Windows clients</secondary>
</indexterm>
<para><application>Samba</application> is a popular open source
software package that provides file and print services using the
<acronym>SMB/CIFS</acronym> protocol. This protocol is built
into &microsoft.windows; systems. It can be added to
non-&microsoft.windows; systems by installing the
<application>Samba</application> client libraries. The protocol
allows clients to access shared data and printers. These shares
can be mapped as a local disk drive and shared printers can be
used as if they were local printers.</para>
<para>On &os;, the <application>Samba</application> client
libraries can be installed using the
<package>net/samba-smbclient</package> port or package. The
client provides the ability for a &os; system to access
<acronym>SMB/CIFS</acronym> shares in a &microsoft.windows;
network.</para>
<para>A &os; system can also be configured to act as a
<application>Samba</application> server by installing the
<package>net/samba46</package> port or package. This allows the
administrator to create <acronym>SMB</acronym>/<acronym>CIFS</acronym>
shares on
the &os; system which can be accessed by clients running
&microsoft.windows; or the <application>Samba</application>
client libraries.</para>
<sect2>
<title>Server Configuration</title>
<para><application>Samba</application> is configured in
<filename>/usr/local/etc/smb4.conf</filename>. This file must
be created before <application>Samba</application>
can be used.</para>
<para>A simple <filename>smb4.conf</filename> to share
directories and printers with &windows; clients in a
workgroup is shown here. For more complex setups
involving LDAP or Active Directory, it is easier to use
&man.samba-tool.8; to create the initial
<filename>smb4.conf</filename>.</para>
<programlisting>[global]
workgroup = WORKGROUP
server string = Samba Server Version %v
netbios name = ExampleMachine
wins support = Yes
security = user
passdb backend = tdbsam
# Example: share /usr/src accessible only to 'developer' user
[src]
path = /usr/src
valid users = developer
writable = yes
browsable = yes
read only = no
guest ok = no
public = no
create mask = 0666
directory mask = 0755</programlisting>
<sect3>
<title>Global Settings</title>
<para>Settings that describe the network are added in
<filename>/usr/local/etc/smb4.conf</filename>:</para>
<variablelist>
<varlistentry>
<term><literal>workgroup</literal></term>
<listitem>
<para>The name of the workgroup to be served.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>netbios name</literal></term>
<listitem>
<para>The NetBIOS name by which a
<application>Samba</application> server is known. By
default, it is the same as the first component of the
host's <acronym>DNS</acronym> name.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>server string</literal></term>
<listitem>
<para>The string that will be displayed in the output of
<command>net view</command> and some other
networking tools that seek to display descriptive text
about the server.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>wins support</literal></term>
<listitem>
<para>Whether <application>Samba</application> will
act as a <acronym>WINS</acronym> server. Do not
enable support for <acronym>WINS</acronym> on more than
one server on the network.</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3>
<title>Security Settings</title>
<para>The most important settings in
<filename>/usr/local/etc/smb4.conf</filename> are the
security model and the backend password format. These
directives control the options:</para>
<variablelist>
<varlistentry>
<term><literal>security</literal></term>
<listitem>
<para>The most common settings are
<literal>security = share</literal> and
<literal>security = user</literal>. If the clients
use usernames that are the same as their usernames on
the &os; machine, user level security should be
used. This is the default security policy and it
requires clients to first log on before they can
access shared resources.</para>
<para>In share level security, clients do not need to
log onto the server with a valid username and password
before attempting to connect to a shared resource.
This was the default security model for older versions
of <application>Samba</application>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>passdb backend</literal></term>
<listitem>
<indexterm><primary>NIS+</primary></indexterm>
<indexterm><primary>LDAP</primary></indexterm>
<indexterm><primary>SQL database</primary></indexterm>
<para><application>Samba</application> has several
different backend authentication models. Clients may
be authenticated with LDAP, NIS+, an SQL database,
or a modified password file. The recommended
authentication method, <literal>tdbsam</literal>,
is ideal for simple networks and is covered here.
For larger or more complex networks,
<literal>ldapsam</literal> is recommended.
<literal>smbpasswd</literal>
was the former default and is now obsolete.</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3>
<title><application>Samba</application> Users</title>
<para>&os; user accounts must be mapped to the
<literal>SambaSAMAccount</literal> database for
&windows; clients to access the share.
Map existing &os; user accounts using
&man.pdbedit.8;:</para>
<screen>&prompt.root; <userinput>pdbedit -a <replaceable>username</replaceable></userinput></screen>
<para>This section has only mentioned the most commonly used
settings. Refer to the <link
xlink:href="http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/">Official
Samba HOWTO</link> for additional information about the
available configuration options.</para>
</sect3>
</sect2>
<sect2>
<title>Starting <application>Samba</application></title>
<para>To enable <application>Samba</application> at boot time,
add the following line to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>samba_enable="YES"</programlisting>
<para>To enable Samba4, use:</para>
<programlisting>samba_server_enable="YES"</programlisting>
<para>To start <application>Samba</application> now:</para>
<screen>&prompt.root; <userinput>service samba start</userinput>
Starting SAMBA: removing stale tdbs :
Starting nmbd.
Starting smbd.</screen>
<para><application>Samba</application> consists of three
separate daemons. Both the <application>nmbd</application>
and <application>smbd</application> daemons are started by
<varname>samba_enable</varname>. If winbind name resolution
is also required, set:</para>
<programlisting>winbindd_enable="YES"</programlisting>
<para><application>Samba</application> can be stopped at any
time by typing:</para>
<screen>&prompt.root; <userinput>service samba stop</userinput></screen>
<para><application>Samba</application> is a complex software
suite with functionality that allows broad integration with
&microsoft.windows; networks. For more information about
functionality beyond the basic configuration described here,
refer to <uri
xlink:href="http://www.samba.org">http://www.samba.org</uri>.</para>
</sect2>
</sect1>
<sect1 xml:id="network-ntp">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Hukins</surname>
<contrib>Contributed by </contrib>
</author>
</authorgroup>
</sect1info>
-->
<title>Clock Synchronization with NTP</title>
<indexterm><primary>NTP</primary>
<secondary>ntpd</secondary>
</indexterm>
<para>Over time, a computer's clock is prone to drift. This is
problematic as many network services require the computers on a
network to share the same accurate time. Accurate time is also
needed to ensure that file timestamps stay consistent. The
Network Time Protocol (<acronym>NTP</acronym>) is one way to
provide clock accuracy in a network.</para>
<para>&os; includes &man.ntpd.8; which can be configured to query
other <acronym>NTP</acronym> servers in order to synchronize the
clock on that machine or to provide time services to other
computers in the network. The servers which are queried can be
local to the network or provided by an <acronym>ISP</acronym>.
In addition, an <link
xlink:href="http://support.ntp.org/bin/view/Servers/WebHome">online
list of publicly accessible <acronym>NTP</acronym>
servers</link> is available. When choosing a public
<acronym>NTP</acronym> server, select one that is geographically
close and review its usage policy.</para>
<para>Choosing several <acronym>NTP</acronym> servers is
recommended in case one of the servers becomes unreachable or
its clock proves unreliable. As <application>ntpd</application>
receives responses, it favors reliable servers over the less
reliable ones.</para>
<para>This section describes how to configure
<application>ntpd</application> on &os;. Further documentation
can be found in <filename>/usr/share/doc/ntp/</filename> in HTML
format.</para>
<sect2>
<title><acronym>NTP</acronym> Configuration</title>
<indexterm><primary>NTP</primary>
<secondary>ntp.conf</secondary>
</indexterm>
<para>On &os;, the built-in <application>ntpd</application> can
be used to synchronize a system's clock. To enable
<application>ntpd</application> at boot time, add
<literal>ntpd_enable="YES"</literal> to
<filename>/etc/rc.conf</filename>. Additional variables can
be specified in <filename>/etc/rc.conf</filename>. Refer to
&man.rc.conf.5; and &man.ntpd.8; for
details.</para>
<para>This application reads <filename>/etc/ntp.conf</filename>
to determine which <acronym>NTP</acronym> servers to query.
Here is a simple example of an
<filename>/etc/ntp.conf</filename>:</para>
<example>
<title> Sample <filename>/etc/ntp.conf</filename></title>
<programlisting>server ntplocal.example.com prefer
server timeserver.example.org
server ntp2a.example.net
driftfile /var/db/ntp.drift</programlisting>
</example>
<para>The format of this file is described in &man.ntp.conf.5;.
The <literal>server</literal> option specifies which servers
to query, with one server listed on each line. If a server
entry includes <literal>prefer</literal>, that server is
preferred over other servers. A response from a preferred
server will be discarded if it differs significantly from
other servers' responses; otherwise it will be used. The
<literal>prefer</literal> argument should only be used for
<acronym>NTP</acronym> servers that are known to be highly
accurate, such as those with special time monitoring
hardware.</para>
<para>The <literal>driftfile</literal> entry specifies which
file is used to store the system clock's frequency offset.
<application>ntpd</application> uses this to automatically
compensate for the clock's natural drift, allowing it to
maintain a reasonably correct setting even if it is cut off
from all external time sources for a period of time. This
file also stores information about previous responses
from <acronym>NTP</acronym> servers. Since this file contains
internal information for <acronym>NTP</acronym>, it should not
be modified.</para>
<para>By default, an <acronym>NTP</acronym> server is accessible
to any network host. The <literal>restrict</literal> option
in <filename>/etc/ntp.conf</filename> can be used to control
which systems can access the server. For example, to deny all
machines from accessing the <acronym>NTP</acronym> server, add
the following line to
<filename>/etc/ntp.conf</filename>:</para>
<programlisting>restrict default ignore</programlisting>
<note>
<para>This will also prevent access from other
<acronym>NTP</acronym> servers. If there is a need to
synchronize with an external <acronym>NTP</acronym> server,
allow only that specific server. Refer to &man.ntp.conf.5;
for more information.</para>
</note>
<para>To allow machines within the network to synchronize their
clocks with the server, but ensure they are not allowed to
configure the server or be used as peers to synchronize
against, instead use:</para>
<programlisting>restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap</programlisting>
<para>where <systemitem
class="ipaddress">192.168.1.0</systemitem> is the local
network address and <systemitem
class="netmask">255.255.255.0</systemitem> is the network's
subnet mask.</para>
<para>Multiple <literal>restrict</literal> entries are
supported. For more details, refer to the <literal>Access
Control Support</literal> subsection of
&man.ntp.conf.5;.</para>
<para>Once <literal>ntpd_enable="YES"</literal> has been added
to <filename>/etc/rc.conf</filename>,
<application>ntpd</application> can be started now without
rebooting the system by typing:</para>
<screen>&prompt.root; <userinput>service ntpd start</userinput></screen>
</sect2>
<sect2>
<title>Using <acronym>NTP</acronym> with a
<acronym>PPP</acronym> Connection</title>
<para><application>ntpd</application> does not need a permanent
connection to the Internet to function properly. However, if
a <acronym>PPP</acronym> connection is configured to dial out
on demand, <acronym>NTP</acronym> traffic should be prevented
from triggering a dial out or keeping the connection alive.
This can be configured with <literal>filter</literal>
directives in <filename>/etc/ppp/ppp.conf</filename>. For
example:</para>
<programlisting> set filter dial 0 deny udp src eq 123
# Prevent NTP traffic from initiating dial out
set filter dial 1 permit 0 0
set filter alive 0 deny udp src eq 123
# Prevent incoming NTP traffic from keeping the connection open
set filter alive 1 deny udp dst eq 123
# Prevent outgoing NTP traffic from keeping the connection open
set filter alive 2 permit 0/0 0/0</programlisting>
<para>For more details, refer to the
<literal>PACKET FILTERING</literal> section in &man.ppp.8; and
the examples in
<filename>/usr/share/examples/ppp/</filename>.</para>
<note>
<para>Some Internet access providers block low-numbered ports,
preventing NTP from functioning since replies never reach
the machine.</para>
</note>
</sect2>
</sect1>
<sect1 xml:id="network-iscsi">
<!--
<sect1info>
<authorgroup>
<author>
<firstname>Edward Tomasz</firstname>
<surname>Napierala</surname>
</author>
</authorgroup>
</sect1info>
-->
<title><acronym>iSCSI</acronym> Initiator and Target
Configuration</title>
<para><acronym>iSCSI</acronym> is a way to share storage over a
network. Unlike <acronym>NFS</acronym>, which works at the file
system level, <acronym>iSCSI</acronym> works at the block device
level.</para>
<para>In <acronym>iSCSI</acronym> terminology, the system that
shares the storage is known as the <emphasis>target</emphasis>.
The storage can be a physical disk, or an area representing
multiple disks or a portion of a physical disk. For example, if
the disk(s) are formatted with <acronym>ZFS</acronym>, a zvol
can be created to use as the <acronym>iSCSI</acronym>
storage.</para>
<para>The clients which access the <acronym>iSCSI</acronym>
storage are called <emphasis>initiators</emphasis>. To
initiators, the storage available through
<acronym>iSCSI</acronym> appears as a raw, unformatted disk
known as a <acronym>LUN</acronym>. Device nodes for the disk
appear in <filename>/dev/</filename> and the device must be
separately formatted and mounted.</para>
<para>Beginning with 10.0-RELEASE, &os; provides a native,
kernel-based <acronym>iSCSI</acronym> target and initiator.
This section describes how to configure a &os; system as a
target or an initiator.</para>
<sect2 xml:id="network-iscsi-target">
<title>Configuring an <acronym>iSCSI</acronym> Target</title>
<note>
<para>The native <acronym>iSCSI</acronym> target is supported
starting with &os; 10.0-RELEASE. To use
<acronym>iSCSI</acronym> in older versions of &os;, install
a userspace target from the Ports Collection, such as
<package>net/istgt</package>. This chapter only describes
the native target.</para>
</note>
<para>To configure an <acronym>iSCSI</acronym> target, create
the <filename>/etc/ctl.conf</filename> configuration file, add
a line to <filename>/etc/rc.conf</filename> to make sure the
&man.ctld.8; daemon is automatically started at boot, and then
start the daemon.</para>
<para>The following is an example of a simple
<filename>/etc/ctl.conf</filename> configuration file. Refer
to &man.ctl.conf.5; for a more complete description of this
file's available options.</para>
<programlisting>portal-group pg0 {
discovery-auth-group no-authentication
listen 0.0.0.0
listen [::]
}
target iqn.2012-06.com.example:target0 {
auth-group no-authentication
portal-group pg0
lun 0 {
path /data/target0-0
size 4G
}
}</programlisting>
<para>The first entry defines the <literal>pg0</literal> portal
group. Portal groups define which network addresses the
&man.ctld.8; daemon will listen on. The
<literal>discovery-auth-group no-authentication</literal>
entry indicates that any initiator is allowed to perform
<acronym>iSCSI</acronym> target discovery without
authentication. Lines three and four configure &man.ctld.8;
to listen on all <acronym>IPv4</acronym>
(<literal>listen 0.0.0.0</literal>) and
<acronym>IPv6</acronym> (<literal>listen [::]</literal>)
addresses on the default port of 3260.</para>
<para>It is not necessary to define a portal group as there is a
built-in portal group called <literal>default</literal>. In
this case, the difference between <literal>default</literal>
and <literal>pg0</literal> is that with
<literal>default</literal>, target discovery is always denied,
while with <literal>pg0</literal>, it is always
allowed.</para>
<para>The second entry defines a single target. Target has two
possible meanings: a machine serving <acronym>iSCSI</acronym>
or a named group of <acronym>LUNs</acronym>. This example
uses the latter meaning, where
<literal>iqn.2012-06.com.example:target0</literal> is the
target name. This target name is suitable for testing
purposes. For actual use, change
<literal>com.example</literal> to the real domain name,
reversed. The <literal>2012-06</literal> represents the year
and month of acquiring control of that domain name, and
<literal>target0</literal> can be any value. Any number of
targets can be defined in this configuration file.</para>
<para>The <literal>auth-group no-authentication</literal> line
allows all initiators to connect to the specified target and
<literal>portal-group pg0</literal> makes the target reachable
through the <literal>pg0</literal> portal group.</para>
<para>The next section defines the <acronym>LUN</acronym>. To
the initiator, each <acronym>LUN</acronym> will be visible as
a separate disk device. Multiple <acronym>LUNs</acronym> can
be defined for each target. Each <acronym>LUN</acronym> is
identified by a number, where <acronym>LUN</acronym> 0 is
mandatory. The <literal>path /data/target0-0</literal> line
defines the full path to a file or zvol backing the
<acronym>LUN</acronym>. That path must exist before starting
&man.ctld.8;. The second line is optional and specifies the
size of the <acronym>LUN</acronym>.</para>
<para>Next, to make sure the &man.ctld.8; daemon is started at
boot, add this line to
<filename>/etc/rc.conf</filename>:</para>
<programlisting>ctld_enable="YES"</programlisting>
<para>To start &man.ctld.8; now, run this command:</para>
<screen>&prompt.root; <userinput>service ctld start</userinput></screen>
<para>As the &man.ctld.8; daemon is started, it reads
<filename>/etc/ctl.conf</filename>. If this file is edited
after the daemon starts, use this command so that the changes
take effect immediately:</para>
<screen>&prompt.root; <userinput>service ctld reload</userinput></screen>
<sect3>
<title>Authentication</title>
<para>The previous example is inherently insecure as it uses
no authentication, granting anyone full access to all
targets. To require a username and password to access
targets, modify the configuration as follows:</para>
<programlisting>auth-group ag0 {
chap username1 secretsecret
chap username2 anothersecret
}
portal-group pg0 {
discovery-auth-group no-authentication
listen 0.0.0.0
listen [::]
}
target iqn.2012-06.com.example:target0 {
auth-group ag0
portal-group pg0
lun 0 {
path /data/target0-0
size 4G
}
}</programlisting>
<para>The <literal>auth-group</literal> section defines
username and password pairs. An initiator trying to connect
to <literal>iqn.2012-06.com.example:target0</literal> must
first specify a defined username and secret. However,
target discovery is still permitted without authentication.
To require target discovery authentication, set
<literal>discovery-auth-group</literal> to a defined
<literal>auth-group</literal> name instead of
<literal>no-authentication</literal>.</para>
<para>It is common to define a single exported target for
every initiator. As a shorthand for the syntax above, the
username and password can be specified directly in the
target entry:</para>
<programlisting>target iqn.2012-06.com.example:target0 {
portal-group pg0
chap username1 secretsecret
lun 0 {
path /data/target0-0
size 4G
}
}</programlisting>
</sect3>
</sect2>
<sect2 xml:id="network-iscsi-initiator">
<title>Configuring an <acronym>iSCSI</acronym> Initiator</title>
<note>
<para>The <acronym>iSCSI</acronym> initiator described in this
section is supported starting with &os; 10.0-RELEASE. To
use the <acronym>iSCSI</acronym> initiator available in
older versions, refer to &man.iscontrol.8;.</para>
</note>
<para>The <acronym>iSCSI</acronym> initiator requires that the
&man.iscsid.8; daemon is running. This daemon does not use a
configuration file. To start it automatically at boot, add
this line to <filename>/etc/rc.conf</filename>:</para>
<programlisting>iscsid_enable="YES"</programlisting>
<para>To start &man.iscsid.8; now, run this command:</para>
<screen>&prompt.root; <userinput>service iscsid start</userinput></screen>
<para>Connecting to a target can be done with or without an
<filename>/etc/iscsi.conf</filename> configuration file. This
section demonstrates both types of connections.</para>
<sect3>
<title>Connecting to a Target Without a Configuration
File</title>
<para>To connect an initiator to a single target, specify the
<acronym>IP</acronym> address of the portal and the name of
the target:</para>
<screen>&prompt.root; <userinput>iscsictl -A -p <replaceable>10.10.10.10</replaceable> -t <replaceable>iqn.2012-06.com.example:target0</replaceable></userinput></screen>
<para>To verify if the connection succeeded, run
<command>iscsictl</command> without any arguments. The
output should look similar to this:</para>
<programlisting>Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Connected: da0</programlisting>
<para>In this example, the <acronym>iSCSI</acronym> session
was successfully established, with
<filename>/dev/da0</filename> representing the attached
<acronym>LUN</acronym>. If the
<literal>iqn.2012-06.com.example:target0</literal> target
exports more than one <acronym>LUN</acronym>, multiple
device nodes will be shown in that section of the
output:</para>
<screen>Connected: da0 da1 da2.</screen>
<para>Any errors will be reported in the output, as well as
the system logs. For example, this message usually means
that the &man.iscsid.8; daemon is not running:</para>
<programlisting>Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Waiting for iscsid(8)</programlisting>
<para>The following message suggests a networking problem,
such as a wrong <acronym>IP</acronym> address or
port:</para>
<programlisting>Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.11 Connection refused</programlisting>
<para>This message means that the specified target name is
wrong:</para>
<programlisting>Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Not found</programlisting>
<para>This message means that the target requires
authentication:</para>
<programlisting>Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Authentication failed</programlisting>
<para>To specify a <acronym>CHAP</acronym> username and
secret, use this syntax:</para>
<screen>&prompt.root; <userinput>iscsictl -A -p <replaceable>10.10.10.10</replaceable> -t <replaceable>iqn.2012-06.com.example:target0</replaceable> -u <replaceable>user</replaceable> -s <replaceable>secretsecret</replaceable></userinput></screen>
</sect3>
<sect3>
<title>Connecting to a Target with a Configuration
File</title>
<para>To connect using a configuration file, create
<filename>/etc/iscsi.conf</filename> with contents like
this:</para>
<programlisting>t0 {
TargetAddress = 10.10.10.10
TargetName = iqn.2012-06.com.example:target0
AuthMethod = CHAP
chapIName = user
chapSecret = secretsecret
}</programlisting>
<para>The <literal>t0</literal> specifies a nickname for the
configuration file section. It will be used by the
initiator to specify which configuration to use. The other
lines specify the parameters to use during connection. The
<literal>TargetAddress</literal> and
<literal>TargetName</literal> are mandatory, whereas the
other options are optional. In this example, the
<acronym>CHAP</acronym> username and secret are
shown.</para>
<para>To connect to the defined target, specify the
nickname:</para>
<screen>&prompt.root; <userinput>iscsictl -An <replaceable>t0</replaceable></userinput></screen>
<para>Alternately, to connect to all targets defined in the
configuration file, use:</para>
<screen>&prompt.root; <userinput>iscsictl -Aa</userinput></screen>
<para>To make the initiator automatically connect to all
targets in <filename>/etc/iscsi.conf</filename>, add the
following to <filename>/etc/rc.conf</filename>:</para>
<programlisting>iscsictl_enable="YES"
iscsictl_flags="-Aa"</programlisting>
</sect3>
</sect2>
</sect1>
</chapter>

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