Index: head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml (revision 47505) +++ head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml (revision 47506) @@ -1,5788 +1,5788 @@ Network Servers Synopsis 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. By the end of this chapter, readers will know: How to manage the inetd daemon. How to set up the Network File System (NFS). How to set up the Network Information Server (NIS) for centralizing and sharing user accounts. How to set &os; up to act as an LDAP server or client How to set up automatic network settings using DHCP. How to set up a Domain Name Server (DNS). How to set up the Apache HTTP Server. How to set up a File Transfer Protocol (FTP) server. How to set up a file and print server for &windows; clients using Samba. How to synchronize the time and date, and set up a time server using the Network Time Protocol (NTP). How to set up iSCSI. This chapter assumes a basic knowledge of: /etc/rc scripts. Network terminology. Installation of additional third-party software (). The <application>inetd</application> Super-Server 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 inetd service needs to be started. When a connection is received for a service that is managed by inetd, it determines which program the connection is destined for, spawns a process for that program, and delegates the program a socket. Using inetd for services that are not heavily used can reduce system load, when compared to running each daemon individually in stand-alone mode. Primarily, inetd is used to spawn other daemons, but several trivial protocols are handled internally, such as chargen, auth, time, echo, discard, and daytime. This section covers the basics of configuring inetd. Configuration File Configuration of inetd is done by editing /etc/inetd.conf. Each line of this configuration file represents an application which can be started by inetd. By default, every line starts with a comment (#), meaning that inetd is not listening for any applications. To configure inetd to listen for an application's connections, remove the # at the beginning of the line for that application. After saving your edits, configure inetd to start at system boot by editing /etc/rc.conf: inetd_enable="YES" To start inetd now, so that it listens for the service you configured, type: &prompt.root; service inetd start Once inetd is started, it needs to be notified whenever a modification is made to /etc/inetd.conf: Reloading the <application>inetd</application> Configuration File &prompt.root; service inetd reload Typically, the default entry for an application does not need to be edited beyond removing the #. In some situations, it may be appropriate to edit the default entry. As an example, this is the default entry for &man.ftpd.8; over IPv4: ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l The seven columns in an entry are as follows: 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 where: service-name The service name of the daemon to start. It must correspond to a service listed in /etc/services. This determines which port inetd listens on for incoming connections to that service. When using a custom service, it must first be added to /etc/services. socket-type Either stream, dgram, raw, or seqpacket. Use stream for TCP connections and dgram for UDP services. protocol Use one of the following protocol names: Protocol Name Explanation tcp or tcp4 TCP IPv4 udp or udp4 UDP IPv4 tcp6 TCP IPv6 udp6 UDP IPv6 tcp46 Both TCP IPv4 and IPv6 udp46 Both UDP IPv4 and IPv6 {wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]] In this field, or must be specified. , and are optional. indicates whether or not the service is able to handle its own socket. socket types must use while daemons, which are usually multi-threaded, should use . usually hands off multiple sockets to a single daemon, while spawns a child daemon for each new socket. The maximum number of child daemons inetd may spawn is set by . For example, to limit ten instances of the daemon, place a /10 after . Specifying /0 allows an unlimited number of children. limits the number of connections from any particular IP 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 /10 would limit any particular IP address to ten connection attempts per minute. limits the number of child processes that can be started on behalf on any single IP address at any moment. These options can limit excessive resource consumption and help to prevent Denial of Service attacks. An example can be seen in the default settings for &man.fingerd.8;: finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -k -s user The username the daemon will run as. Daemons typically run as root, daemon, or nobody. server-program The full path to the daemon. If the daemon is a service provided by inetd internally, use . server-program-arguments Used to specify any command arguments to be passed to the daemon on invocation. If the daemon is an internal service, use . Command-Line Options Like most server daemons, inetd has a number of options that can be used to modify its behaviour. By default, inetd is started with -wW -C 60. These options enable TCP wrappers for all services, including internal services, and prevent any IP address from requesting any service more than 60 times per minute. To change the default options which are passed to inetd, add an entry for inetd_flags in /etc/rc.conf. If inetd is already running, restart it with service inetd restart. The available rate limiting options are: -c maximum 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 in /etc/inetd.conf. -C rate Specify the default maximum number of times a service can be invoked from a single IP address per minute. May be overridden on a per-service basis by using in /etc/inetd.conf. -R rate Specify the maximum number of times a service can be invoked in one minute, where the default is 256. A rate of 0 allows an unlimited number. -s maximum Specify the maximum number of times a service can be invoked from a single IP address at any one time, where the default is unlimited. May be overridden on a per-service basis by using in /etc/inetd.conf. Additional options are available. Refer to &man.inetd.8; for the full list of options. Security Considerations Many of the daemons which can be managed by inetd are not security-conscious. Some daemons, such as fingerd, 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. max-connections-per-ip-per-minute, max-child and max-child-per-ip can be used to limit such attacks. By default, TCP wrappers is enabled. Consult &man.hosts.access.5; for more information on placing TCP restrictions on various inetd invoked daemons. Network File System (NFS) Tom Rhodes Reorganized and enhanced by Bill Swingle Written by NFS &os; supports the Network File System (NFS), which allows a server to share directories and files with clients over a network. With NFS, users and programs can access files on remote systems as if they were stored locally. NFS has many practical uses. Some of the more common uses include: Data that would otherwise be duplicated on each client can be kept in a single location and accessed by clients on the network. Several clients may need access to the /usr/ports/distfiles directory. Sharing that directory allows for quick access to the source files without having to download them to each client. On large networks, it is often more convenient to configure a central NFS 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. Administration of NFS exports is simplified. For example, there is only one file system where security or backup policies must be set. 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. NFS 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. These daemons must be running on the server: NFS server file server UNIX clients rpcbind mountd nfsd Daemon Description nfsd The NFS daemon which services requests from NFS clients. mountd The NFS mount daemon which carries out requests received from nfsd. rpcbind This daemon allows NFS clients to discover which port the NFS server is using. Running &man.nfsiod.8; on the client can improve performance, but is not required. Configuring the Server NFS configuration The file systems which the NFS server will share are specified in /etc/exports. 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. NFS export examples The following /etc/exports 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. This example shows how to export /cdrom to three hosts named alpha, bravo, and charlie: /cdrom -ro alpha bravo charlie The -ro 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 DNS or in /etc/hosts. Refer to &man.hosts.5; if the network does not have a DNS server. The next example exports /home to three clients by IP address. This can be useful for networks without DNS or /etc/hosts entries. The -alldirs 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. /home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4 This next example exports /a so that two clients from different domains may access that file system. The allows root on the remote system to write data on the exported file system as root. If -maproot=root is not specified, the client's root user will be mapped to the server's nobody account and will be subject to the access limitations defined for nobody. /a -maproot=root host.example.com box.example.org A client can only be specified once per file system. For example, if /usr is a single file system, these entries would be invalid as both entries specify the same host: # Invalid when /usr is one file system /usr/src client /usr/ports client The correct format for this situation is to use one entry: /usr/src /usr/ports client The following is an example of a valid export list, where /usr and /exports are local file systems: # 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 To enable the processes required by the NFS server at boot time, add these options to /etc/rc.conf: rpcbind_enable="YES" nfs_server_enable="YES" mountd_flags="-r" The server can be started now by running this command: &prompt.root; service nfsd start Whenever the NFS server is started, mountd also starts automatically. However, mountd only reads /etc/exports when it is started. To make subsequent /etc/exports edits take effect immediately, force mountd to reread it: &prompt.root; service mountd reload Configuring the Client To enable NFS clients, set this option in each client's /etc/rc.conf: nfs_client_enable="YES" Then, run this command on each NFS client: &prompt.root; service nfsclient start The client now has everything it needs to mount a remote file system. In these examples, the server's name is server and the client's name is client. To mount /home on server to the /mnt mount point on client: NFS mounting &prompt.root; mount server:/home /mnt The files and directories in /home will now be available on client, in the /mnt directory. To mount a remote file system each time the client boots, add it to /etc/fstab: server:/home /mnt nfs rw 0 0 Refer to &man.fstab.5; for a description of all available options. Locking Some applications require file locking to operate correctly. To enable locking, add these lines to /etc/rc.conf on both the client and server: rpc_lockd_enable="YES" rpc_statd_enable="YES" Then start the applications: &prompt.root; service lockd start &prompt.root; service statd start If locking is not required on the server, the NFS client can be configured to lock locally by including when running mount. Refer to &man.mount.nfs.8; for further details. Automating Mounts with &man.amd.8; Wylie Stilwell Contributed by Chern Lee Rewritten by amd automatic mounter daemon The automatic mounter daemon, amd, 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 amd. This daemon provides an alternative to modifying /etc/fstab to list every client. It operates by attaching itself as an NFS server to the /host and /net directories. When a file is accessed within one of these directories, amd looks up the corresponding remote mount and automatically mounts it. /net is used to mount an exported file system from an IP address while /host is used to mount an export from a remote hostname. For instance, an attempt to access a file within /host/foobar/usr would tell amd to mount the /usr export on the host foobar. Mounting an Export with <application>amd</application> In this example, showmount -e shows the exported file systems that can be mounted from the NFS server, foobar: &prompt.user; showmount -e foobar Exports list on foobar: /usr 10.10.10.0 /a 10.10.10.0 &prompt.user; cd /host/foobar/usr The output from showmount shows /usr as an export. When changing directories to /host/foobar/usr, amd intercepts the request and attempts to resolve the hostname foobar. If successful, amd automatically mounts the desired export. To enable amd at boot time, add this line to /etc/rc.conf: amd_enable="YES" To start amd now: &prompt.root; service amd start Custom flags can be passed to amd from the amd_flags environment variable. By default, amd_flags is set to: amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map" The default options with which exports are mounted are defined in /etc/amd.map. Some of the more advanced features of amd are defined in /etc/amd.conf. Consult &man.amd.8; and &man.amd.conf.5; for more information. Automating Mounts with &man.autofs.5; The &man.autofs.5; automount facility is supported starting with &os; 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. autofs automounter subsystem 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. The &man.autofs.5; virtual filesystem is mounted on specified mountpoints by &man.automount.8;, usually invoked during boot. 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. The primary autofs configuration file is /etc/auto_master. It assigns individual maps to top-level mounts. For an explanation of auto_master and the map syntax, refer to &man.auto.master.5;. There is a special automounter map mounted on /net. 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 /net/foobar/usr would tell &man.automountd.8; to mount the /usr export from the host foobar. Mounting an Export with &man.autofs.5; In this example, showmount -e shows the exported file systems that can be mounted from the NFS server, foobar: &prompt.user; showmount -e foobar Exports list on foobar: /usr 10.10.10.0 /a 10.10.10.0 &prompt.user; cd /net/foobar/usr The output from showmount shows /usr as an export. When changing directories to /host/foobar/usr, &man.automountd.8; intercepts the request and attempts to resolve the hostname foobar. If successful, &man.automountd.8; automatically mounts the source export. To enable &man.autofs.5; at boot time, add this line to /etc/rc.conf: autofs_enable="YES" Then &man.autofs.5; can be started by running: &prompt.root; service automount start &prompt.root; service automountd start &prompt.root; service autounmountd start The &man.autofs.5; map format is the same as in other operating systems, it might be desirable to consult information from other operating systems, such as the Mac OS X document. Consult the &man.automount.8;, &man.automountd.8;, &man.autounmountd.8;, and &man.auto.master.5; manual pages for more information. Network Information System (<acronym>NIS</acronym>) NIS Solaris HP-UX AIX Linux NetBSD OpenBSD yellow pages NIS Network Information System (NIS) is designed to centralize administration of &unix;-like systems such as &solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, and &os;. NIS was originally known as Yellow Pages but the name was changed due to trademark issues. This is the reason why NIS commands begin with yp. NIS domains NIS is a Remote Procedure Call (RPC)-based client/server system that allows a group of machines within an NIS domain to share a common set of configuration files. This permits a system administrator to set up NIS client systems with only minimal configuration data and to add, remove, or modify configuration data from a single location. &os; uses version 2 of the NIS protocol. <acronym>NIS</acronym> Terms and Processes Table 28.1 summarizes the terms and important processes used by NIS: rpcbind portmap <acronym>NIS</acronym> Terminology Term Description NIS domain name NIS servers and clients share an NIS domain name. Typically, this name does not have anything to do with DNS. &man.rpcbind.8; This service enables RPC and must be running in order to run an NIS server or act as an NIS client. &man.ypbind.8; This service binds an NIS client to its NIS server. It will take the NIS domain name and use RPC to connect to the server. It is the core of client/server communication in an NIS environment. If this service is not running on a client machine, it will not be able to access the NIS server. &man.ypserv.8; This is the process for the NIS server. If this service stops running, the server will no longer be able to respond to NIS 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 ypbind process may need to be restarted on these clients. &man.rpc.yppasswdd.8; This process only runs on NIS master servers. This daemon allows NIS clients to change their NIS passwords. If this daemon is not running, users will have to login to the NIS master server and change their passwords there.
Machine Types NIS master server NIS slave server NIS client There are three types of hosts in an NIS environment: NIS master server This server acts as a central repository for host configuration information and maintains the authoritative copy of the files used by all of the NIS clients. The passwd, group, and other various files used by NIS clients are stored on the master server. While it is possible for one machine to be an NIS master server for more than one NIS domain, this type of configuration will not be covered in this chapter as it assumes a relatively small-scale NIS environment. NIS slave servers NIS slave servers maintain copies of the NIS master's data files in order to provide redundancy. Slave servers also help to balance the load of the master server as NIS clients always attach to the NIS server which responds first. NIS clients NIS clients authenticate against the NIS server during log on. Information in many files can be shared using NIS. The master.passwd, group, and hosts files are commonly shared via NIS. Whenever a process on a client needs information that would normally be found in these files locally, it makes a query to the NIS server that it is bound to instead. Planning Considerations This section describes a sample NIS environment which consists of 15 &os; machines with no centralized point of administration. Each machine has its own /etc/passwd and /etc/master.passwd. 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. The configuration of the lab will be as follows: Machine name IP address Machine role ellington 10.0.0.2 NIS master coltrane 10.0.0.3 NIS slave basie 10.0.0.4 Faculty workstation bird 10.0.0.5 Client machine cli[1-11] 10.0.0.[6-17] Other client machines If this is the first time an NIS 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. Choosing a <acronym>NIS</acronym> Domain Name NIS domain name When a client broadcasts its requests for info, it includes the name of the NIS 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 NIS domain name as the name for a group of hosts. Some organizations choose to use their Internet domain name for their NIS domain name. This is not recommended as it can cause confusion when trying to debug network problems. The NIS 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 acme-art NIS domain. This example will use the domain name test-domain. However, some non-&os; operating systems require the NIS 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 must be used as the NIS domain name. Physical Server Requirements There are several things to keep in mind when choosing a machine to use as a NIS server. Since NIS clients depend upon the availability of the server, choose a machine that is not rebooted frequently. The NIS server should ideally be a stand alone machine whose sole purpose is to be an NIS server. If the network is not heavily used, it is acceptable to put the NIS server on a machine running other services. However, if the NIS server becomes unavailable, it will adversely affect all NIS clients. Configuring the <acronym>NIS</acronym> Master Server The canonical copies of all NIS files are stored on the master server. The databases used to store the information are called NIS maps. In &os;, these maps are stored in /var/yp/[domainname] where [domainname] is the name of the NIS 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. NIS master and slave servers handle all NIS requests through &man.ypserv.8;. This daemon is responsible for receiving incoming requests from NIS 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. NIS server configuration Setting up a master NIS server can be relatively straight forward, depending on environmental needs. Since &os; provides built-in NIS support, it only needs to be enabled by adding the following lines to /etc/rc.conf: nisdomainname="test-domain" nis_server_enable="YES" nis_yppasswdd_enable="YES" This line sets the NIS domain name to test-domain. This automates the start up of the NIS server processes when the system boots. This enables the &man.rpc.yppasswdd.8; daemon so that users can change their NIS password from a client machine. Care must be taken in a multi-server domain where the server machines are also NIS 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. A server that is also a client can be forced to bind to a particular server by adding these additional lines to /etc/rc.conf: nis_client_enable="YES" # run client stuff as well nis_client_flags="-S NIS domain,server" After saving the edits, type /etc/netstart to restart the network and apply the values defined in /etc/rc.conf. Before initializing the NIS maps, start &man.ypserv.8;: &prompt.root; service ypserv start Initializing the <acronym>NIS</acronym> Maps NIS maps NIS maps are generated from the configuration files in /etc on the NIS master, with one exception: /etc/master.passwd. This is to prevent the propagation of passwords to all the servers in the NIS domain. Therefore, before the NIS maps are initialized, configure the primary password files: &prompt.root; cp /etc/master.passwd /var/yp/master.passwd &prompt.root; cd /var/yp &prompt.root; vi master.passwd 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 NIS clients, such as the root and any other administrative accounts. Ensure that the /var/yp/master.passwd is neither group or world readable by setting its permissions to 600. After completing this task, initialize the NIS maps. &os; includes the &man.ypinit.8; script to do this. When generating maps for the master server, include and specify the NIS domain name: ellington&prompt.root; ypinit -m test-domain 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] n 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 <control D>. master server : ellington next host to add: coltrane next host to add: ^D The current list of NIS servers looks like this: ellington coltrane Is this correct? [y/n: y] y [..output from map generation..] NIS Map update completed. ellington has been setup as an YP master server without any errors. This will create /var/yp/Makefile from /var/yp/Makefile.dist. By default, this file assumes that the environment has a single NIS server with only &os; clients. Since test-domain has a slave server, edit this line in /var/yp/Makefile so that it begins with a comment (#): NOPUSH = "True" Adding New Users Every time a new user is created, the user account must be added to the master NIS server and the NIS maps rebuilt. Until this occurs, the new user will not be able to login anywhere except on the NIS master. For example, to add the new user jsmith to the test-domain domain, run these commands on the master server: &prompt.root; pw useradd jsmith &prompt.root; cd /var/yp &prompt.root; make test-domain The user could also be added using adduser jsmith instead of pw useradd smith. Setting up a <acronym>NIS</acronym> Slave Server NIS slave server To set up an NIS slave server, log on to the slave server and edit /etc/rc.conf as for the master server. Do not generate any NIS maps, as these already exist on the master server. When running ypinit on the slave server, use (for slave) instead of (for master). This option requires the name of the NIS master in addition to the domain name, as seen in this example: coltrane&prompt.root; ypinit -s ellington test-domain 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] n 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. This will generate a directory on the slave server called /var/yp/test-domain which contains copies of the NIS master server's maps. Adding these /etc/crontab entries on each slave server will force the slaves to sync their maps with the maps on the master server: 20 * * * * root /usr/libexec/ypxfr passwd.byname 21 * * * * root /usr/libexec/ypxfr passwd.byuid 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. To finish the configuration, run /etc/netstart on the slave server in order to start the NIS services. Setting Up an <acronym>NIS</acronym> Client An NIS client binds to an NIS 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 NIS server in the same domain receives one of the broadcasts, it will respond to ypbind, 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 NIS requests to that server. The client will automatically ping 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, ypbind will mark the domain as unbound and begin broadcasting again in the hopes of locating another server. NIS client configuration To configure a &os; machine to be an NIS client: Edit /etc/rc.conf and add the following lines in order to set the NIS domain name and start &man.ypbind.8; during network startup: nisdomainname="test-domain" nis_client_enable="YES" To import all possible password entries from the NIS server, use vipw to remove all user accounts except one from /etc/master.passwd. When removing the accounts, keep in mind that at least one local account should remain and this account should be a member of wheel. If there is a problem with NIS, 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: +::::::::: This line configures the client to provide anyone with a valid account in the NIS server's password maps an account on the client. There are many ways to configure the NIS client by modifying this line. One method is described in . For more detailed reading, refer to the book Managing NFS and NIS, published by O'Reilly Media. To import all possible group entries from the NIS server, add this line to /etc/group: +:*:: To start the NIS client immediately, execute the following commands as the superuser: &prompt.root; /etc/netstart &prompt.root; service ypbind start After completing these steps, running ypcat passwd on the client should show the server's passwd map. <acronym>NIS</acronym> Security Since RPC is a broadcast-based service, any system running ypbind within the same domain can retrieve the contents of the NIS maps. To prevent unauthorized transactions, &man.ypserv.8; supports a feature called securenets which can be used to restrict access to a given set of hosts. By default, this information is stored in /var/yp/securenets, unless &man.ypserv.8; is started with 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 # are considered to be comments. A sample securenets might look like this: # 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 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 securenets does not exist, ypserv will allow connections from any host. is an alternate mechanism for providing access control instead of securenets. While either access control mechanism adds some security, they are both vulnerable to IP spoofing attacks. All NIS-related traffic should be blocked at the firewall. Servers using securenets may fail to serve legitimate NIS 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 securenets. TCP Wrapper The use of TCP Wrapper increases the latency of the NIS server. The additional delay may be long enough to cause timeouts in client programs, especially in busy networks with slow NIS servers. If one or more clients suffer from latency, convert those clients into NIS slave servers and force them to bind to themselves. Barring Some Users In this example, the basie system is a faculty workstation within the NIS domain. The passwd map on the master NIS server contains accounts for both faculty and students. This section demonstrates how to allow faculty logins on this system while refusing student logins. To prevent specified users from logging on to a system, even if they are present in the NIS database, use vipw to add -username with the correct number of colons towards the end of /etc/master.passwd on the client, where username is the username of a user to bar from logging in. The line with the blocked user must be before the + line that allows NIS users. In this example, bill is barred from logging on to basie: basie&prompt.root; cat /etc/master.passwd 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 &:/:/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; Using Netgroups netgroups Barring specified users from logging on to individual systems becomes unscaleable on larger networks and quickly loses the main benefit of NIS: centralized administration. 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. To expand on the example used in this chapter, the NIS domain will be extended to add the users and systems shown in Tables 28.2 and 28.3: Additional Users User Name(s) Description alpha, beta IT department employees charlie, delta IT department apprentices echo, foxtrott, golf, ... employees able, baker, ... interns
Additional Systems Machine Name(s) Description war, death, famine, pollution Only IT employees are allowed to log onto these servers. pride, greed, envy, wrath, lust, sloth All members of the IT department are allowed to login onto these servers. one, two, three, four, ... Ordinary workstations used by employees. trashcan A very old machine without any critical data. Even interns are allowed to use this system.
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 NIS setup is planned carefully, only one central configuration file needs modification to grant or deny access to machines. The first step is the initialization of the NIS netgroup map. In &os;, this map is not created by default. On the NIS master server, use an editor to create a map named /var/yp/netgroup. This example creates four netgroups to represent IT employees, IT apprentices, employees, and interns: 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) 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: 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. The name of the account that belongs to this netgroup. The NIS domain for the account. Accounts may be imported from other NIS domains into a netgroup. If a group contains multiple users, separate each user with whitespace. Additionally, each field may contain wildcards. See &man.netgroup.5; for details. netgroups 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. Some non-&os; NIS 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: BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...] BIGGRP2 (,joe16,domain) (,joe17,domain) [...] BIGGRP3 (,joe31,domain) (,joe32,domain) BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3 Repeat this process if more than 225 (15 times 15) users exist within a single netgroup. To activate and distribute the new NIS map: ellington&prompt.root; cd /var/yp ellington&prompt.root; make This will generate the three NIS maps netgroup, netgroup.byhost and netgroup.byuser. Use the map key option of &man.ypcat.1; to check if the new NIS maps are available: ellington&prompt.user; ypcat -k netgroup ellington&prompt.user; ypcat -k netgroup.byhost ellington&prompt.user; ypcat -k netgroup.byuser The output of the first command should resemble the contents of /var/yp/netgroup. 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. To configure a client, use &man.vipw.8; to specify the name of the netgroup. For example, on the server named war, replace this line: +::::::::: with +@IT_EMP::::::::: This specifies that only the users defined in the netgroup IT_EMP will be imported into this system's password database and only those users are allowed to login to this system. This configuration also applies to the ~ function of the shell and all routines which convert between user names and numerical user IDs. In other words, cd ~user will not work, ls -l will show the numerical ID instead of the username, and find . -user joe -print will fail with the message No such user. To fix this, import all user entries without allowing them to login into the servers. This can be achieved by adding an extra line: +:::::::::/sbin/nologin This line configures the client to import all entries but to replace the shell in those entries with /sbin/nologin. Make sure that extra line is placed after +@IT_EMP:::::::::. Otherwise, all user accounts imported from NIS will have /sbin/nologin as their login shell and no one will be able to login to the system. To configure the less important servers, replace the old +::::::::: on the servers with these lines: +@IT_EMP::::::::: +@IT_APP::::::::: +:::::::::/sbin/nologin The corresponding lines for the workstations would be: +@IT_EMP::::::::: +@USERS::::::::: +:::::::::/sbin/nologin 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 BIGSRV to define the login restrictions for the important servers, another netgroup called SMALLSRV for the less important servers, and a third netgroup called USERBOX for the workstations. Each of these netgroups contains the netgroups that are allowed to login onto these machines. The new entries for the NIS netgroup map would look like this: BIGSRV IT_EMP IT_APP SMALLSRV IT_EMP IT_APP ITINTERN USERBOX IT_EMP ITINTERN USERS 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. Machine-specific netgroup definitions are another possibility to deal with the policy changes. In this scenario, the /etc/master.passwd of each system contains two lines starting with +. The first line adds a netgroup with the accounts allowed to login onto this machine and the second line adds all other accounts with /sbin/nologin as shell. It is recommended to use the ALL-CAPS version of the hostname as the name of the netgroup: +@BOXNAME::::::::: +:::::::::/sbin/nologin Once this task is completed on all the machines, there is no longer a need to modify the local versions of /etc/master.passwd ever again. All further changes can be handled by modifying the NIS map. Here is an example of a possible netgroup map for this scenario: # 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] 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 NIS map within reasonable limits. Password Formats NIS password formats NIS requires that all hosts within an NIS domain use the same format for encrypting passwords. If users have trouble authenticating on an NIS client, it may be due to a differing password format. In a heterogeneous network, the format must be supported by all operating systems, where DES is the lowest common standard. To check which format a server or client is using, look at this section of /etc/login.conf: default:\ :passwd_format=des:\ :copyright=/etc/COPYRIGHT:\ [Further entries elided] In this example, the system is using the DES format. Other possible values are blf for Blowfish and md5 for MD5 encrypted passwords. If the format on a host needs to be edited to match the one being used in the NIS domain, the login capability database must be rebuilt after saving the change: &prompt.root; cap_mkdb /etc/login.conf The format of passwords for existing user accounts will not be updated until each user changes their password after the login capability database is rebuilt. Lightweight Directory Access Protocol (<acronym>LDAP</acronym>) Tom Rhodes Written by LDAP The Lightweight Directory Access Protocol (LDAP) 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 OpenLDAP 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 LDAP server's record base. This section provides a quick start guide for configuring an LDAP 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. <acronym>LDAP</acronym> Terminology and Structure LDAP uses several terms which should be understood before starting the configuration. All directory entries consist of a group of attributes. Each of these attribute sets contains a unique identifier known as a Distinguished Name (DN) which is normally built from several other attributes such as the common or Relative Distinguished Name (RDN). Similar to how directories have absolute and relative paths, consider a DN as an absolute path and the RDN as the relative path. An example LDAP entry looks like the following. This example searches for the entry for the specified user account (uid), organizational unit (ou), and organization (o): &prompt.user; ldapsearch -xb "uid=trhodes,ou=users,o=example.com" # extended LDIF # # LDAPv3 # base <uid=trhodes,ou=users,o=example.com> 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 This example entry shows the values for the dn, mail, cn, uid, and telephoneNumber attributes. The cn attribute is the RDN. More information about LDAP and its terminology can be found at http://www.openldap.org/doc/admin24/intro.html. Configuring an <acronym>LDAP</acronym> Server LDAP Server &os; does not provide a built-in LDAP server. Begin the configuration by installing the net/openldap24-server package or port. Since the port has many configurable options, it is recommended that the default options are reviewed to see if the package is sufficient, and to instead compile the port if any options should be changed. In most cases, the defaults are fine. However, if SQL support is needed, this option must be enabled and the port compiled using the instructions in . Next, create the directories to hold the data and to store the certificates: &prompt.root; mkdir /var/db/openldap-data &prompt.root; mkdir /usr/local/etc/openldap/private Copy over the database configuration file: &prompt.root; cp /usr/local/etc/openldap/DB_CONFIG.example /var/db/openldap-data/DB_CONFIG The next phase is to configure the certificate authority. The following commands must be executed from /usr/local/etc/openldap/private. 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, start with this command and follow the prompts: &prompt.root; openssl req -days 365 -nodes -new -x509 -keyout ca.key -out ../ca.crt The entries for the prompts may be generic except for the Common Name. This entry must be different than the system hostname. If this will be a self signed certificate, prefix the hostname with CA for certificate authority. The next task is to create a certificate signing request and a private key. Input this command and follow the prompts: &prompt.root; openssl req -days 365 -nodes -new -keyout server.key -out server.csr During the certificate generation process, be sure to correctly set the Common Name attribute. Once complete, sign the key: &prompt.root; openssl x509 -req -days 365 -in server.csr -out ../server.crt -CA ../ca.crt -CAkey ca.key -CAcreateserial The final part of the certificate generation process is to generate and sign the client certificates: &prompt.root; openssl req -days 365 -nodes -new -keyout client.key -out client.csr &prompt.root; openssl x509 -req -days 3650 -in client.csr -out ../client.crt -CA ../ca.crt -CAkey ca.key Remember to use the same Common Name attribute when prompted. When finished, ensure that a total of eight (8) new files have been generated through the proceeding commands. If so, the next step is to edit /usr/local/etc/openldap/slapd.conf and add the following options: TLSCipherSuite HIGH:MEDIUM:+SSLv3 TLSCertificateFile /usr/local/etc/openldap/server.crt TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key TLSCACertificateFile /usr/local/etc/openldap/ca.crt Then, edit /usr/local/etc/openldap/ldap.conf and add the following lines: TLS_CACERT /usr/local/etc/openldap/ca.crt TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3 While editing this file, uncomment the following entries and set them to the desired values: , , and . Set the to contain and . Then, add two entries pointing to the certificate authority. When finished, the entries should look similar to the following: BASE dc=example,dc=com URI ldap:// ldaps:// SIZELIMIT 12 TIMELIMIT 15 TLS_CACERT /usr/local/etc/openldap/ca.crt TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3 The default password for the server should then be changed: &prompt.root; slappasswd -h "{SHA}" >> /usr/local/etc/openldap/slapd.conf This command will prompt for the password and, if the process does not fail, a password hash will be added to the end of slapd.conf. Several hashing formats are supported. Refer to the manual page for slappasswd for more information. Next, edit /usr/local/etc/openldap/slapd.conf and add the following lines: password-hash {sha} allow bind_v2 The in this file must be updated to match the used in /usr/local/etc/openldap/ldap.conf and should also be set. A recommended value for is something like . Before saving this file, place the in front of the password output from slappasswd and delete the old . The end result should look similar to this: TLSCipherSuite HIGH:MEDIUM:+SSLv3 TLSCertificateFile /usr/local/etc/openldap/server.crt TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key TLSCACertificateFile /usr/local/etc/openldap/ca.crt rootpw {SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g= Finally, enable the OpenLDAP service in /etc/rc.conf and set the URI: slapd_enable="YES" slapd_flags="-4 -h ldaps:///" At this point the server can be started and tested: &prompt.root; service slapd start If everything is configured correctly, a search of the directory should show a successful connection with a single response as in this example: &prompt.root; ldapsearch -Z # extended LDIF # # LDAPv3 # base <dc=example,dc=com> (default) with scope subtree # filter: (objectclass=*) # requesting: ALL # # search result search: 3 result: 32 No such object # numResponses: 1 If the command fails and the configuration looks correct, stop the slapd service and restart it with debugging options: &prompt.root; service slapd stop &prompt.root; /usr/local/libexec/slapd -d -1 Once the service is responding, the directory can be populated using ldapadd. In this example, a file containing this list of users is first created. Each user should use the following format: dn: dc=example,dc=com objectclass: dcObject objectclass: organization o: Example dc: Example dn: cn=Manager,dc=example,dc=com objectclass: organizationalRole cn: Manager To import this file, specify the file name. The following command will prompt for the password specified earlier and the output should look something like this: &prompt.root; ldapadd -Z -D "cn=Manager,dc=example,dc=com" -W -f import.ldif Enter LDAP Password: adding new entry "dc=example,dc=com" adding new entry "cn=Manager,dc=example,dc=com" Verify the data was added by issuing a search on the server using ldapsearch: &prompt.user; ldapsearch -Z # extended LDIF # # LDAPv3 # base <dc=example,dc=com> (default) with scope subtree # filter: (objectclass=*) # requesting: ALL # # example.com dn: dc=example,dc=com objectClass: dcObject objectClass: organization o: Example dc: Example # Manager, example.com dn: cn=Manager,dc=example,dc=com objectClass: organizationalRole cn: Manager # search result search: 3 result: 0 Success # numResponses: 3 # numEntries: 2 At this point, the server should be configured and functioning properly. Dynamic Host Configuration Protocol (<acronym>DHCP</acronym>) Dynamic Host Configuration Protocol DHCP Internet Systems Consortium (ISC) The Dynamic Host Configuration Protocol (DHCP) 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 dhclient which is used by the client to obtain the addressing information. &os; does not install a DHCP server, but several servers are available in the &os; Ports Collection. The DHCP protocol is fully described in RFC 2131. Informational resources are also available at isc.org/downloads/dhcp/. This section describes how to use the built-in DHCP client. It then describes how to install and configure a DHCP server. In &os;, the &man.bpf.4; device is needed by both the DHCP server and DHCP client. This device is included in the GENERIC kernel that is installed with &os;. Users who prefer to create a custom kernel need to keep this device if DHCP is used. It should be noted that bpf also allows privileged users to run network packet sniffers on that system. Configuring a <acronym>DHCP</acronym> Client DHCP 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 DHCP server. Refer to for examples of network configuration. UDP When dhclient is executed on the client machine, it begins broadcasting requests for configuration information. By default, these requests use UDP port 68. The server replies on UDP port 67, giving the client an IP address and other relevant network information such as a subnet mask, default gateway, and DNS server addresses. This information is in the form of a DHCP lease and is valid for a configurable time. This allows stale IP addresses for clients no longer connected to the network to automatically be reused. DHCP clients can obtain a great deal of information from the server. An exhaustive list may be found in &man.dhcp-options.5;. By default, when a &os; system boots, its DHCP client runs in the background, or asynchronously. Other startup scripts continue to run while the DHCP process completes, which speeds up system startup. Background DHCP works well when the DHCP server responds quickly to the client's requests. However, DHCP may take a long time to complete on some systems. If network services attempt to run before DHCP has assigned the network addressing information, they will fail. Using DHCP in synchronous mode prevents this problem as it pauses startup until the DHCP configuration has completed. This line in /etc/rc.conf is used to configure background or asynchronous mode: ifconfig_fxp0="DHCP" This line may already exist if the system was configured to use DHCP during installation. Replace the fxp0 shown in these examples with the name of the interface to be dynamically configured, as described in . To instead configure the system to use synchronous mode, and to pause during startup while DHCP completes, use SYNCDHCP: ifconfig_fxp0="SYNCDHCP" Additional client options are available. Search for dhclient in &man.rc.conf.5; for details. DHCP configuration files The DHCP client uses the following files: /etc/dhclient.conf The configuration file used by dhclient. Typically, this file contains only comments as the defaults are suitable for most clients. This configuration file is described in &man.dhclient.conf.5;. /sbin/dhclient More information about the command itself can be found in &man.dhclient.8;. /sbin/dhclient-script The &os;-specific DHCP client configuration script. It is described in &man.dhclient-script.8;, but should not need any user modification to function properly. /var/db/dhclient.leases.interface The DHCP client keeps a database of valid leases in this file, which is written as a log and is described in &man.dhclient.leases.5;. Installing and Configuring a <acronym>DHCP</acronym> Server This section demonstrates how to configure a &os; system to act as a DHCP server using the Internet Systems Consortium (ISC) implementation of the DHCP server. This implementation and its documentation can be installed using the net/isc-dhcp42-server package or port. DHCP server DHCP installation The installation of net/isc-dhcp42-server installs a sample configuration file. Copy /usr/local/etc/dhcpd.conf.example to /usr/local/etc/dhcpd.conf and make any edits to this new file. DHCP dhcpd.conf The configuration file is comprised of declarations for subnets and hosts which define the information that is provided to DHCP clients. For example, these lines configure the following: option domain-name "example.org"; option domain-name-servers ns1.example.org; option subnet-mask 255.255.255.0; default-lease-time 600; max-lease-time 72400; ddns-update-style none; subnet 10.254.239.0 netmask 255.255.255.224 { range 10.254.239.10 10.254.239.20; option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org; } host fantasia { hardware ethernet 08:00:07:26:c0:a5; fixed-address fantasia.fugue.com; } This option specifies the default search domain that will be provided to clients. Refer to &man.resolv.conf.5; for more information. This option specifies a comma separated list of DNS servers that the client should use. They can be listed by their Fully Qualified Domain Names (FQDN), as seen in the example, or by their IP addresses. The subnet mask that will be provided to clients. The default lease expiry time in seconds. A client can be configured to override this value. 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 max-lease-time. The default of disables dynamic DNS updates. Changing this to configures the DHCP server to update a DNS server whenever it hands out a lease so that the DNS server knows which IP addresses are associated with which computers in the network. Do not change the default setting unless the DNS server has been configured to support dynamic DNS. This line creates a pool of available IP addresses which are reserved for allocation to DHCP clients. The range of addresses must be valid for the network or subnet specified in the previous line. Declares the default gateway that is valid for the network or subnet specified before the opening { bracket. Specifies the hardware MAC address of a client so that the DHCP server can recognize the client when it makes a request. Specifies that this host should always be given the same IP address. Using the hostname is correct, since the DHCP server will resolve the hostname before returning the lease information. This configuration file supports many more options. Refer to dhcpd.conf(5), installed with the server, for details and examples. Once the configuration of dhcpd.conf is complete, enable the DHCP server in /etc/rc.conf: dhcpd_enable="YES" dhcpd_ifaces="dc0" Replace the dc0 with the interface (or interfaces, separated by whitespace) that the DHCP server should listen on for DHCP client requests. Start the server by issuing the following command: &prompt.root; service isc-dhcpd start Any future changes to the configuration of the server will require the dhcpd service to be stopped and then started using &man.service.8;. The DHCP server uses the following files. Note that the manual pages are installed with the server software. DHCP configuration files /usr/local/sbin/dhcpd More information about the dhcpd server can be found in dhcpd(8). /usr/local/etc/dhcpd.conf 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). /var/db/dhcpd.leases The DHCP 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. /usr/local/sbin/dhcrelay This daemon is used in advanced environments where one DHCP server forwards a request from a client to another DHCP server on a separate network. If this functionality is required, install the net/isc-dhcp42-relay package or port. The installation includes dhcrelay(8) which provides more detail. Domain Name System (<acronym>DNS</acronym>) DNS Domain Name System (DNS) is the protocol through which domain names are mapped to IP addresses, and vice versa. DNS is coordinated across the Internet through a somewhat complex system of authoritative root, Top Level Domain (TLD), and other smaller-scale name servers, which host and cache individual domain information. It is not necessary to run a name server to perform DNS lookups on a system. BIND In &os; 10, the Berkeley Internet Name Domain (BIND) has been removed from the base system and replaced with Unbound. Unbound as configured in the &os; Base is a local caching resolver. BIND is still available from The Ports Collection as dns/bind99 or dns/bind98. In &os; 9 and lower, BIND is included in &os; Base. The &os; version provides enhanced security features, a new file system layout, and automated &man.chroot.8; configuration. BIND is maintained by the Internet Systems Consortium. resolver reverse DNS root zone The following table describes some of the terms associated with DNS: <acronym>DNS</acronym> Terminology Term Definition Forward DNS Mapping of hostnames to IP addresses. Origin Refers to the domain covered in a particular zone file. named, BIND Common names for the BIND name server package within &os;. Resolver A system process through which a machine queries a name server for zone information. Reverse DNS Mapping of IP addresses to hostnames. Root zone 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. Zone An individual domain, subdomain, or portion of the DNS administered by the same authority.
zones examples Examples of zones: . is how the root zone is usually referred to in documentation. org. is a Top Level Domain (TLD) under the root zone. example.org. is a zone under the org. TLD. 1.168.192.in-addr.arpa is a zone referencing all IP addresses which fall under the 192.168.1.* IP address space. As one can see, the more specific part of a hostname appears to its left. For example, example.org. is more specific than org., as org. is more specific than the root zone. The layout of each part of a hostname is much like a file system: the /dev directory falls within the root, and so on. Reasons to Run a Name Server Name servers generally come in two forms: authoritative name servers, and caching (also known as resolving) name servers. An authoritative name server is needed when: One wants to serve DNS information to the world, replying authoritatively to queries. A domain, such as example.org, is registered and IP addresses need to be assigned to hostnames under it. An IP address block requires reverse DNS entries (IP to hostname). A backup or second name server, called a slave, will reply to queries. A caching name server is needed when: A local DNS server may cache and respond more quickly than querying an outside name server. When one queries for www.FreeBSD.org, the resolver usually queries the uplink ISP's name server, and retrieves the reply. With a local, caching DNS server, the query only has to be made once to the outside world by the caching DNS server. Additional queries will not have to go outside the local network, since the information is cached locally. <acronym>DNS</acronym> Server Configuration in &os; 10.0 and Later In &os; 10.0, BIND has been replaced with Unbound. Unbound is a validating caching resolver only. If an authoritative server is needed, many are available from the Ports Collection. Unbound is provided in the &os; base system. By default, it will provide DNS 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 Unbound from the &os; Ports Collection. To enable Unbound, add the following to /etc/rc.conf: local_unbound_enable="YES" Any existing nameservers in /etc/resolv.conf will be configured as forwarders in the new Unbound configuration. If any of the listed nameservers do not support DNSSEC, local DNS 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 192.168.1.1: &prompt.user; drill -S FreeBSD.org @192.168.1.1 Once each nameserver is confirmed to support DNSSEC, start Unbound: &prompt.root; service local_unbound onestart This will take care of updating /etc/resolv.conf so that queries for DNSSEC secured domains will now work. For example, run the following to validate the FreeBSD.org DNSSEC trust tree: &prompt.user; drill -S FreeBSD.org ;; 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 DNS Server Configuration in &os; - 9.<replaceable>X</replaceable> and Earlier + 9.X In &os;, the BIND daemon is called named. File Description &man.named.8; The BIND daemon. &man.rndc.8; Name server control utility. /etc/namedb Directory where BIND zone information resides. /etc/namedb/named.conf Configuration file of the daemon. Depending on how a given zone is configured on the server, the files related to that zone can be found in the master, slave, or dynamic subdirectories of the /etc/namedb directory. These files contain the DNS information that will be given out by the name server in response to queries. Starting BIND BIND starting Since BIND is installed by default, configuring it is relatively simple. The default named 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: &prompt.root; service named onestart To ensure the named daemon is started at boot each time, put the following line into the /etc/rc.conf: named_enable="YES" There are many configuration options for /etc/namedb/named.conf that are beyond the scope of this document. Other startup options for named on &os; can be found in the named_* flags in /etc/defaults/rc.conf and in &man.rc.conf.5;. The section is also a good read. Configuration Files BIND configuration files Configuration files for named currently reside in /etc/namedb 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. <filename>/etc/namedb/named.conf</filename> // $FreeBSD$ // // 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've got 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"; Just as the comment says, to benefit from an uplink's cache, forwarders 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. 127.0.0.1 will not work here. Change this IP address to a name server at the uplink. /* Modern versions of BIND use a random UDP 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, don't 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: Don't 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; }; }; */ In named.conf, these are examples of slave entries for a forward and reverse zone. For each new zone served, a new zone entry must be added to named.conf. For example, the simplest zone entry for example.org can look like: zone "example.org" { type master; file "master/example.org"; }; The zone is a master, as indicated by the statement, holding its zone information in /etc/namedb/master/example.org indicated by the statement. zone "example.org" { type slave; file "slave/example.org"; }; 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. Zone Files BIND zone files An example master zone file for example.org (existing within /etc/namedb/master/example.org) is as follows: $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. Note that every hostname ending in a . is an exact hostname, whereas everything without a trailing . is relative to the origin. For example, ns1 is translated into ns1.example.org. The format of a zone file follows: recordname IN recordtype value DNS records The most commonly used DNS records: SOA start of zone authority NS an authoritative name server A a host address CNAME the canonical name for an alias MX mail exchanger PTR a domain name pointer (used in reverse DNS) 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 example.org. the domain name, also the origin for this zone file. ns1.example.org. the primary/authoritative name server for this zone. admin.example.org. the responsible person for this zone, email address with @ replaced. (admin@example.org becomes admin.example.org) 2006051501 the serial number of the file. This must be incremented each time the zone file is modified. Nowadays, many admins prefer a yyyymmddrr format for the serial number. 2006051501 would mean last modified 05/15/2006, the latter 01 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. IN NS ns1.example.org. This is an NS entry. Every name server that is going to reply authoritatively for the zone must have one of these entries. 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 The A record indicates machine names. As seen above, ns1.example.org would resolve to 192.168.1.2. IN A 192.168.1.1 This line assigns IP address 192.168.1.1 to the current origin, in this case example.org. www IN CNAME @ The canonical name record is usually used for giving aliases to a machine. In the example, www is aliased to the master machine whose name happens to be the same as the domain name example.org (192.168.1.1). CNAMEs can never be used together with another kind of record for the same hostname. MX record IN MX 10 mail.example.org. The MX record indicates which mail servers are responsible for handling incoming mail for the zone. mail.example.org is the hostname of a mail server, and 10 is the priority of that mail server. One can have several mail servers, with priorities of 10, 20 and so on. A mail server attempting to deliver to example.org 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. For in-addr.arpa zone files (reverse DNS), the same format is used, except with PTR entries instead of A or CNAME. $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. This file gives the proper IP address to hostname mappings for the above fictitious domain. 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 .). Caching Name Server BIND caching name server 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. <acronym role="Domain Name Security Extensions">DNSSEC</acronym> BIND DNS security extensions Domain Name System Security Extensions, or DNSSEC for short, is a suite of specifications to protect resolving name servers from forged DNS data, such as spoofed DNS records. By using digital signatures, a resolver can verify the integrity of the record. Note that DNSSEC only provides integrity via digitally signing the Resource Records (RRs). It provides neither confidentiality nor protection against false end-user assumptions. This means that it cannot protect against people going to example.net instead of example.com. The only thing DNSSEC does is authenticate that the data has not been compromised in transit. The security of DNS is an important step in securing the Internet in general. For more in-depth details of how DNSSEC works, the relevant RFCs are a good place to start. See the list in . The following sections will demonstrate how to enable DNSSEC for an authoritative DNS server and a recursive (or caching) DNS server running BIND 9. While all versions of BIND 9 support DNSSEC, it is necessary to have at least version 9.6.2 in order to be able to use the signed root zone when validating DNS 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 BIND 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. Recursive <acronym>DNS</acronym> Server Configuration Enabling DNSSEC validation of queries performed by a recursive DNS server requires a few changes to named.conf. 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 BIND 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 dig. By running &prompt.user; dig +multi +noall +answer DNSKEY . > root.dnskey the key will end up in root.dnskey. The contents should look something like this: . 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 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 (SEP), commonly known as a Key Signing Key (KSK). The second key, with value 256, is a subordinate key, commonly called a Zone Signing Key (ZSK). More on the different key types later in . Now the key must be verified and formatted so that BIND can use it. To verify the key, generate a DS RR set. Create a file containing these RRs with &prompt.user; dnssec-dsfromkey -f root.dnskey . > root.ds These records use SHA-1 and SHA-256 respectively, and should look similar to the following example, where the longer is using SHA-256. . IN DS 19036 8 1 B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E . IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5 The SHA-256 RR can now be compared to the digest in https://data.iana.org/root-anchors/root-anchors.xml. To be absolutely sure that the key has not been tampered with the data in the XML file can be verified using the PGP signature in https://data.iana.org/root-anchors/root-anchors.asc. Next, the key must be formatted properly. This differs a little between BIND 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 managed-keys as seen in the example below. When using the older version, the key is added using a trusted-keys statement and updates must be done manually. For BIND 9.6.2 the format should look like: trusted-keys { "." 257 3 8 "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq QxA+Uk1ihz0="; }; For 9.7 the format will instead be: managed-keys { "." initial-key 257 3 8 "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq QxA+Uk1ihz0="; }; The root key can now be added to named.conf either directly or by including a file containing the key. After these steps, configure BIND to do DNSSEC validation on queries by editing named.conf and adding the following to the options directive: dnssec-enable yes; dnssec-validation yes; To verify that it is actually working use dig to make a query for a signed zone using the resolver just configured. A successful reply will contain the AD flag to indicate the data was authenticated. Running a query such as &prompt.user; dig @resolver +dnssec se ds should return the DS RR for the .se zone. In the flags: section the AD flag should be set, as seen in: ... ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1 ... The resolver is now capable of authenticating DNS queries. Authoritative <acronym>DNS</acronym> Server Configuration In order to get an authoritative name server to serve a DNSSEC 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 (KSK) that is not rotated very often and a Zone Signing Key (ZSK) that is rotated more frequently. Information on recommended operational practices can be found in RFC 4641: DNSSEC Operational Practices. Practices regarding the root zone can be found in DNSSEC Practice Statement for the Root Zone KSK operator and DNSSEC Practice Statement for the Root Zone ZSK operator. The KSK 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 (SEP) key. A message digest of this key, called a Delegation Signer (DS) record, must be published in the parent zone to establish the trust chain. How this is accomplished depends on the parent zone owner. The ZSK is used to sign the zone, and only needs to be published there. To enable DNSSEC for the example.com zone depicted in previous examples, the first step is to use dnssec-keygen to generate the KSK and ZSK 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 KSK for example.com, run &prompt.user; dnssec-keygen -f KSK -a RSASHA256 -b 2048 -n ZONE example.com and to generate the ZSK, run &prompt.user; dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com dnssec-keygen outputs two files, the public and the private keys in files named similar to Kexample.com.+005+nnnnn.key (public) and Kexample.com.+005+nnnnn.private (private). The nnnnn 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 KSK file do: &prompt.user; mv Kexample.com.+005+nnnnn.key Kexample.com.+005+nnnnn.KSK.key &prompt.user; mv Kexample.com.+005+nnnnn.private Kexample.com.+005+nnnnn.KSK.private For the ZSK files, substitute KSK for ZSK as necessary. The files can now be included in the zone file, using the $include statement. It should look something like this: $include Kexample.com.+005+nnnnn.KSK.key ; KSK $include Kexample.com.+005+nnnnn.ZSK.key ; ZSK Finally, sign the zone and tell BIND to use the signed zone file. To sign a zone dnssec-signzone is used. The command to sign the zone example.com, located in example.com.db would look similar to &prompt.user; dnssec-signzone -o example.com -k Kexample.com.+005+nnnnn.KSK example.com.db Kexample.com.+005+nnnnn.ZSK.key The key supplied to the argument is the KSK and the other key file is the ZSK that should be used in the signing. It is possible to supply more than one KSK and ZSK, 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 dnssec-signzone is a zone file with all RRs signed. This output will end up in a file with the extension .signed, such as example.com.db.signed. The DS records will also be written to a separate file dsset-example.com. To use this signed zone just modify the zone directive in named.conf to use example.com.db.signed. 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. 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 DNS data unavailable for a time, until the new key has propagated through the DNS hierarchy. For more information on key rollovers and other DNSSEC operational issues, see RFC 4641: DNSSEC Operational practices. Automation Using <acronym>BIND</acronym> 9.7 or Later Beginning with BIND version 9.7 a new feature called Smart Signing 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 key repository, and using the new option auto-dnssec, it is possible to create a dynamic zone which will be resigned as needed. To update this zone use nsupdate with the new option . rndc has also grown the ability to sign zones with keys in the key repository, using the option . To tell BIND to use this automatic signing and zone updating for example.com, add the following to named.conf: zone example.com { type master; key-directory "/etc/named/keys"; update-policy local; auto-dnssec maintain; file "/etc/named/dynamic/example.com.zone"; }; After making these changes, generate keys for the zone as explained in , put those keys in the key repository given as the argument to the key-directory in the zone configuration and the zone will be signed automatically. Updates to a zone configured this way must be done using nsupdate, which will take care of re-signing the zone with the new data added. For further details, see and the BIND documentation. Security Although BIND is the most common implementation of DNS, there is always the issue of security. Possible and exploitable security holes are sometimes found. While &os; automatically drops named into a &man.chroot.8; environment; there are several other security mechanisms in place which could help to lure off possible DNS service attacks. It is always good idea to read CERT's security advisories and to subscribe to the &a.security-notifications; to stay up to date with the current Internet and &os; security issues. If a problem arises, keeping sources up to date and having a fresh build of named may help. Further Reading BIND/named manual pages: &man.rndc.8; &man.named.8; &man.named.conf.5; &man.nsupdate.1; &man.dnssec-signzone.8; &man.dnssec-keygen.8; Official ISC BIND Page Official ISC BIND Forum O'Reilly DNS and BIND 5th Edition Root DNSSEC DNSSEC Trust Anchor Publication for the Root Zone RFC1034 - Domain Names - Concepts and Facilities RFC1035 - Domain Names - Implementation and Specification RFC4033 - DNS Security Introduction and Requirements RFC4034 - Resource Records for the DNS Security Extensions RFC4035 - Protocol Modifications for the DNS Security Extensions RFC4641 - DNSSEC Operational Practices RFC 5011 - Automated Updates of DNS Security (DNSSEC Trust Anchors Apache HTTP Server Murray Stokely Contributed by web servers setting up Apache The open source Apache HTTP Server is the most widely used web server. &os; does not install this web server by default, but it can be installed from the www/apache24 package or port. This section summarizes how to configure and start version 2.x of the Apache HTTP Server on &os;. For more detailed information about Apache 2.X and its configuration directives, refer to httpd.apache.org. Configuring and Starting Apache Apache configuration file In &os;, the main Apache HTTP Server configuration file is installed as /usr/local/etc/apache2x/httpd.conf, where x represents the version number. This ASCII text file begins comment lines with a #. The most frequently modified directives are: ServerRoot "/usr/local" Specifies the default directory hierarchy for the Apache installation. Binaries are stored in the bin and sbin subdirectories of the server root and configuration files are stored in the etc/apache2x subdirectory. ServerAdmin you@example.com 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. ServerName www.example.com:80 Allows an administrator to set a hostname which is sent back to clients for the server. For example, www can be used instead of the actual hostname. If the system does not have a registered DNS name, enter its IP address instead. If the server will listen on an alternate report, change 80 to the alternate port number. DocumentRoot "/usr/local/www/apache2x/data" 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. It is always a good idea to make a backup copy of the default Apache configuration file before making changes. When the configuration of Apache is complete, save the file and verify the configuration using apachectl. Running apachectl configtest should return Syntax OK. Apache starting or stopping To launch Apache at system startup, add the following line to /etc/rc.conf: apache24_enable="YES" If Apache should be started with non-default options, the following line may be added to /etc/rc.conf to specify the needed flags: apache24_flags="" If apachectl does not report configuration errors, start httpd now: &prompt.root; service apache24 start The httpd service can be tested by entering http://localhost in a web browser, replacing localhost with the fully-qualified domain name of the machine running httpd. The default web page that is displayed is /usr/local/www/apache24/data/index.html. The Apache configuration can be tested for errors after making subsequent configuration changes while httpd is running using the following command: &prompt.root; service apache24 configtest It is important to note that configtest is not an &man.rc.8; standard, and should not be expected to work for all startup scripts. Virtual Hosting Virtual hosting allows multiple websites to run on one Apache server. The virtual hosts can be IP-based or name-based. IP-based virtual hosting uses a different IP 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 IP address. To setup Apache to use name-based virtual hosting, add a VirtualHost block for each website. For example, for the webserver named www.domain.tld with a virtual domain of www.someotherdomain.tld, add the following entries to httpd.conf: <VirtualHost *> ServerName www.domain.tld DocumentRoot /www/domain.tld </VirtualHost> <VirtualHost *> ServerName www.someotherdomain.tld DocumentRoot /www/someotherdomain.tld </VirtualHost> For each virtual host, replace the values for ServerName and DocumentRoot with the values to be used. For more information about setting up virtual hosts, consult the official Apache documentation at: http://httpd.apache.org/docs/vhosts/. Apache Modules Apache modules Apache uses modules to augment the functionality provided by the basic server. Refer to http://httpd.apache.org/docs/current/mod/ for a complete listing of and the configuration details for the available modules. In &os;, some modules can be compiled with the www/apache24 port. Type make config within /usr/ports/www/apache24 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. <filename>mod_ssl</filename> web servers secure SSL cryptography The mod_ssl module uses the OpenSSL library to provide strong cryptography via the Secure Sockets Layer (SSLv3) and Transport Layer Security (TLSv1) 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;. In &os;, mod_ssl module is enabled by default in both the package and the port. The available configuration directives are explained at http://httpd.apache.org/docs/current/mod/mod_ssl.html. <filename>mod_perl</filename> mod_perl Perl The mod_perl module makes it possible to write Apache modules in Perl. In addition, the persistent interpreter embedded in the server avoids the overhead of starting an external interpreter and the penalty of Perl start-up time. The mod_perl can be installed using the www/mod_perl2 package or port. Documentation for using this module can be found at http://perl.apache.org/docs/2.0/index.html. <filename>mod_php</filename> Tom Rhodes Written by mod_php PHP PHP: Hypertext Preprocessor (PHP) is a general-purpose scripting language that is especially suited for web development. Capable of being embedded into HTML, its syntax draws upon C, &java;, and Perl with the intention of allowing web developers to write dynamically generated webpages quickly. To gain support for PHP5 for the Apache web server, install the www/mod_php5 package or port. This will install and configure the modules required to support dynamic PHP applications. The installation will automatically add this line to /usr/local/etc/apache24/httpd.conf: LoadModule php5_module libexec/apache24/libphp5.so Then, perform a graceful restart to load the PHP module: &prompt.root; apachectl graceful The PHP support provided by www/mod_php5 is limited. Additional support can be installed using the lang/php5-extensions port which provides a menu driven interface to the available PHP extensions. Alternatively, individual extensions can be installed using the appropriate port. For instance, to add PHP support for the MySQL database server, install databases/php5-mysql. After installing an extension, the Apache server must be reloaded to pick up the new configuration changes: &prompt.root; apachectl graceful Dynamic Websites web servers dynamic In addition to mod_perl and mod_php, other languages are available for creating dynamic web content. These include Django and Ruby on Rails. Django Python Django Django 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 Python objects. A rich dynamic database-access API is provided for those objects without the developer ever having to write SQL. It also provides an extensible template system so that the logic of the application is separated from the HTML presentation. Django depends on mod_python, and an SQL database engine. In &os;, the www/py-django port automatically installs mod_python and supports the PostgreSQL, MySQL, or SQLite databases, with the default being SQLite. To change the database engine, type make config within /usr/ports/www/py-django, then install the port. Once Django is installed, the application will need a project directory along with the Apache configuration in order to use the embedded Python interpreter. This interpreter is used to call the application for specific URLs on the site. To configure Apache to pass requests for certain URLs to the web application, add the following to httpd.conf, specifying the full path to the project directory: <Location "/"> SetHandler python-program PythonPath "['/dir/to/the/django/packages/'] + sys.path" PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE mysite.settings PythonAutoReload On PythonDebug On </Location> Refer to https://docs.djangoproject.com/en/1.6/ for more information on how to use Django. Ruby on Rails Ruby on Rails Ruby on Rails 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 www/rubygem-rails package or port. Refer to http://rubyonrails.org/documentation for more information on how to use Ruby on Rails. File Transfer Protocol (<acronym>FTP</acronym>) FTP servers The File Transfer Protocol (FTP) provides users with a simple way to transfer files to and from an FTP server. &os; includes FTP server software, ftpd, in the base system. &os; provides several configuration files for controlling access to the FTP server. This section summarizes these files. Refer to &man.ftpd.8; for more details about the built-in FTP server. Configuration The most important configuration step is deciding which accounts will be allowed access to the FTP server. A &os; system has a number of system accounts which should not be allowed FTP access. The list of users disallowed any FTP access can be found in /etc/ftpusers. By default, it includes system accounts. Additional users that should not be allowed access to FTP can be added. In some cases it may be desirable to restrict the access of some users without preventing them completely from using FTP. This can be accomplished be creating /etc/ftpchroot as described in &man.ftpchroot.5;. This file lists users and groups subject to FTP access restrictions. FTP anonymous To enable anonymous FTP access to the server, create a user named ftp on the &os; system. Users will then be able to log on to the FTP server with a username of ftp or anonymous. When prompted for the password, any input will be accepted, but by convention, an email address should be used as the password. The FTP server will call &man.chroot.2; when an anonymous user logs in, to restrict access to only the home directory of the ftp user. There are two text files that can be created to specify welcome messages to be displayed to FTP clients. The contents of /etc/ftpwelcome will be displayed to users before they reach the login prompt. After a successful login, the contents of /etc/ftpmotd will be displayed. Note that the path to this file is relative to the login environment, so the contents of ~ftp/etc/ftpmotd would be displayed for anonymous users. Once the FTP server has been configured, set the appropriate variable in /etc/rc.conf to start the service during boot: ftpd_enable="YES" To start the service now: &prompt.root; service ftpd start Test the connection to the FTP server by typing: &prompt.user; ftp localhost syslog log files FTP The ftpd daemon uses &man.syslog.3; to log messages. By default, the system log daemon will write messages related to FTP in /var/log/xferlog. The location of the FTP log can be modified by changing the following line in /etc/syslog.conf: ftp.info /var/log/xferlog FTP anonymous Be aware of the potential problems involved with running an anonymous FTP server. In particular, think twice about allowing anonymous users to upload files. It may turn out that the FTP site becomes a forum for the trade of unlicensed commercial software or worse. If anonymous FTP uploads are required, then verify the permissions so that these files can not be read by other anonymous users until they have been reviewed by an administrator. File and Print Services for µsoft.windows; Clients (Samba) Samba server Microsoft Windows file server Windows clients print server Windows clients Samba is a popular open source software package that provides file and print services using the SMB/CIFS protocol. This protocol is built into µsoft.windows; systems. It can be added to non-µsoft.windows; systems by installing the Samba 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. On &os;, the Samba client libraries can be installed using the net/samba-smbclient port or package. The client provides the ability for a &os; system to access SMB/CIFS shares in a µsoft.windows; network. A &os; system can also be configured to act as a Samba server. This allows the administrator to create SMB/CIFS shares on the &os; system which can be accessed by clients running µsoft.windows; or the Samba client libraries. In order to configure a Samba server on &os;, the net/samba36 port or package must first be installed. The rest of this section provides an overview of how to configure a Samba server on &os;. Configuration A default Samba configuration file is installed as /usr/local/share/examples/samba36/smb.conf.default. This file must be copied to /usr/local/etc/smb.conf and customized before Samba can be used. Runtime configuration information for Samba is found in smb.conf, such as definitions of the printers and file system shares that will be shared with &windows; clients. The Samba package includes a web based tool called swat which provides a simple way for configuring smb.conf. Using the Samba Web Administration Tool (SWAT) The Samba Web Administration Tool (SWAT) runs as a daemon from inetd. Therefore, inetd must be enabled as shown in . To enable swat, uncomment the following line in /etc/inetd.conf: swat stream tcp nowait/400 root /usr/local/sbin/swat swat As explained in , the inetd configuration must be reloaded after this configuration file is changed. Once swat has been enabled, use a web browser to connect to http://localhost:901. At first login, enter the credentials for root. Once logged in, the main Samba configuration page and the system documentation will be available. Begin configuration by clicking on the Globals tab. The Globals section corresponds to the variables that are set in the [global] section of /usr/local/etc/smb.conf. Global Settings Whether swat is used or /usr/local/etc/smb.conf is edited directly, the first directives encountered when configuring Samba are: workgroup The domain name or workgroup name for the computers that will be accessing this server. netbios name The NetBIOS name by which a Samba server is known. By default it is the same as the first component of the host's DNS name. server string The string that will be displayed in the output of net view and some other networking tools that seek to display descriptive text about the server. Security Settings Two of the most important settings in /usr/local/etc/smb.conf are the security model and the backend password format for client users. The following directives control these options: security The two most common options are security = share and security = user. 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. 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 Samba. passdb backend NIS+ LDAP SQL database Samba has several different backend authentication models. Clients may be authenticated with LDAP, NIS+, an SQL database, or a modified password file. The default authentication method is smbpasswd, and that is all that will be covered here. Assuming that the default smbpasswd backend is used, /usr/local/etc/samba/smbpasswd must be created to allow Samba to authenticate clients. To provide &unix; user accounts access from &windows; clients, use the following command to add each required user to that file: &prompt.root; smbpasswd -a username The recommended backend is now tdbsam. If this backend is selected, use the following command to add user accounts: &prompt.root; pdbedit -a -u username This section has only mentioned the most commonly used settings. Refer to the Official Samba HOWTO for additional information about the available configuration options. Starting <application>Samba</application> To enable Samba at boot time, add the following line to /etc/rc.conf: samba_enable="YES" Alternately, its services can be started separately: nmbd_enable="YES" smbd_enable="YES" To start Samba now: &prompt.root; service samba start Starting SAMBA: removing stale tdbs : Starting nmbd. Starting smbd. Samba consists of three separate daemons. Both the nmbd and smbd daemons are started by samba_enable. If winbind name resolution services are enabled in smb.conf, the winbindd daemon is started as well. Samba may be stopped at any time by typing: &prompt.root; service samba stop Samba is a complex software suite with functionality that allows broad integration with µsoft.windows; networks. For more information about functionality beyond the basic configuration described here, refer to http://www.samba.org. Clock Synchronization with NTP NTP ntpd 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 (NTP) is one way to provide clock accuracy in a network. &os; includes &man.ntpd.8; which can be configured to query other NTP 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 ISP. In addition, an online list of publicly accessible NTP servers is available. When choosing a public NTP server, select one that is geographically close and review its usage policy. Choosing several NTP servers is recommended in case one of the servers becomes unreachable or its clock proves unreliable. As ntpd receives responses, it favors reliable servers over the less reliable ones. This section describes how to configure ntpd on &os;. Further documentation can be found in /usr/share/doc/ntp/ in HTML format. <acronym>NTP</acronym> Configuration NTP ntp.conf On &os;, the built-in ntpd can be used to synchronize a system's clock. To enable ntpd at boot time, add ntpd_enable="YES" to /etc/rc.conf. Additional variables can be specified in /etc/rc.conf. Refer to &man.rc.conf.5; and &man.ntpd.8; for details. This application reads /etc/ntp.conf to determine which NTP servers to query. Here is a simple example of an /etc/ntp.conf: Sample <filename>/etc/ntp.conf</filename> server ntplocal.example.com prefer server timeserver.example.org server ntp2a.example.net driftfile /var/db/ntp.drift The format of this file is described in &man.ntp.conf.5;. The server option specifies which servers to query, with one server listed on each line. If a server entry includes prefer, 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 prefer argument should only be used for NTP servers that are known to be highly accurate, such as those with special time monitoring hardware. The driftfile entry specifies which file is used to store the system clock's frequency offset. ntpd 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 NTP servers. Since this file contains internal information for NTP, it should not be modified. By default, an NTP server is accessible to any network host. The restrict option in /etc/ntp.conf can be used to control which systems can access the server. For example, to deny all machines from accessing the NTP server, add the following line to /etc/ntp.conf: restrict default ignore This will also prevent access from other NTP servers. If there is a need to synchronize with an external NTP server, allow only that specific server. Refer to &man.ntp.conf.5; for more information. 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: restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap where 192.168.1.0 is the local network address and 255.255.255.0 is the network's subnet mask. Multiple restrict entries are supported. For more details, refer to the Access Control Support subsection of &man.ntp.conf.5;. Once ntpd_enable="YES" has been added to /etc/rc.conf, ntpd can be started now without rebooting the system by typing: &prompt.root; service ntpd start Using <acronym>NTP</acronym> with a <acronym>PPP</acronym> Connection ntpd does not need a permanent connection to the Internet to function properly. However, if a PPP connection is configured to dial out on demand, NTP traffic should be prevented from triggering a dial out or keeping the connection alive. This can be configured with filter directives in /etc/ppp/ppp.conf. For example: 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 For more details, refer to the PACKET FILTERING section in &man.ppp.8; and the examples in /usr/share/examples/ppp/. Some Internet access providers block low-numbered ports, preventing NTP from functioning since replies never reach the machine. <acronym>iSCSI</acronym> Initiator and Target Configuration iSCSI is a way to share storage over a network. Unlike NFS, which works at the file system level, iSCSI works at the block device level. In iSCSI terminology, the system that shares the storage is known as the target. 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 ZFS, a zvol can be created to use as the iSCSI storage. The clients which access the iSCSI storage are called initiators. To initiators, the storage available through iSCSI appears as a raw, unformatted disk known as a LUN. Device nodes for the disk appear in /dev/ and the device must be separately formatted and mounted. Beginning with 10.0-RELEASE, &os; provides a native, kernel-based iSCSI target and initiator. This section describes how to configure a &os; system as a target or an initiator. Configuring an <acronym>iSCSI</acronym> Target The native iSCSI target is supported starting with &os; 10.0-RELEASE. To use iSCSI in older versions of &os;, install a userspace target from the Ports Collection, such as net/istgt. This chapter only describes the native target. To configure an iSCSI target, create the /etc/ctl.conf configuration file, add a line to /etc/rc.conf to make sure the &man.ctld.8; daemon is automatically started at boot, and then start the daemon. The following is an example of a simple /etc/ctl.conf configuration file. Refer to &man.ctl.conf.5; for a more complete description of this file's available options. 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 } } The first entry defines the pg0 portal group. Portal groups define which network addresses the &man.ctld.8; daemon will listen on. The discovery-auth-group no-authentication entry indicates that any initiator is allowed to perform iSCSI target discovery without authentication. Lines three and four configure &man.ctld.8; to listen on all IPv4 (listen 0.0.0.0) and IPv6 (listen [::]) addresses on the default port of 3260. It is not necessary to define a portal group as there is a built-in portal group called default. In this case, the difference between default and pg0 is that with default, target discovery is always denied, while with pg0, it is always allowed. The second entry defines a single target. Target has two possible meanings: a machine serving iSCSI or a named group of LUNs. This example uses the latter meaning, where iqn.2012-06.com.example:target0 is the target name. This target name is suitable for testing purposes. For actual use, change com.example to the real domain name, reversed. The 2012-06 represents the year and month of acquiring control of that domain name, and target0 can be any value. Any number of targets can be defined in this configuration file. The auth-group no-authentication line allows all initiators to connect to the specified target and portal-group pg0 makes the target reachable through the pg0 portal group. The next section defines the LUN. To the initiator, each LUN will be visible as a separate disk device. Multiple LUNs can be defined for each target. Each LUN is identified by a number, where LUN 0 is mandatory. The path /data/target0-0 line defines the full path to a file or zvol backing the LUN. That path must exist before starting &man.ctld.8;. The second line is optional and specifies the size of the LUN. Next, to make sure the &man.ctld.8; daemon is started at boot, add this line to /etc/rc.conf: ctld_enable="YES" To start &man.ctld.8; now, run this command: &prompt.root; service ctld start As the &man.ctld.8; daemon is started, it reads /etc/ctl.conf. If this file is edited after the daemon starts, use this command so that the changes take effect immediately: &prompt.root; service ctld reload Authentication 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: 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 } } The auth-group section defines username and password pairs. An initiator trying to connect to iqn.2012-06.com.example:target0 must first specify a defined username and secret. However, target discovery is still permitted without authentication. To require target discovery authentication, set discovery-auth-group to a defined auth-group name instead of no-authentication. 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: target iqn.2012-06.com.example:target0 { portal-group pg0 chap username1 secretsecret lun 0 { path /data/target0-0 size 4G } } Configuring an <acronym>iSCSI</acronym> Initiator The iSCSI initiator described in this section is supported starting with &os; 10.0-RELEASE. To use the iSCSI initiator available in older versions, refer to &man.iscontrol.8;. The iSCSI 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 /etc/rc.conf: iscsid_enable="YES" To start &man.iscsid.8; now, run this command: &prompt.root; service iscsid start Connecting to a target can be done with or without an /etc/iscsi.conf configuration file. This section demonstrates both types of connections. Connecting to a Target Without a Configuration File To connect an initiator to a single target, specify the IP address of the portal and the name of the target: &prompt.root; iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0 To verify if the connection succeeded, run iscsictl without any arguments. The output should look similar to this: Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Connected: da0 In this example, the iSCSI session was successfully established, with /dev/da0 representing the attached LUN. If the iqn.2012-06.com.example:target0 target exports more than one LUN, multiple device nodes will be shown in that section of the output: Connected: da0 da1 da2. 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: Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Waiting for iscsid(8) The following message suggests a networking problem, such as a wrong IP address or port: Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.11 Connection refused This message means that the specified target name is wrong: Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Not found This message means that the target requires authentication: Target name Target portal State iqn.2012-06.com.example:target0 10.10.10.10 Authentication failed To specify a CHAP username and secret, use this syntax: &prompt.root; iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0 -u user -s secretsecret Connecting to a Target with a Configuration File To connect using a configuration file, create /etc/iscsi.conf with contents like this: t0 { TargetAddress = 10.10.10.10 TargetName = iqn.2012-06.com.example:target0 AuthMethod = CHAP chapIName = user chapSecret = secretsecret } The t0 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 TargetAddress and TargetName are mandatory, whereas the other options are optional. In this example, the CHAP username and secret are shown. To connect to the defined target, specify the nickname: &prompt.root; iscsictl -An t0 Alternately, to connect to all targets defined in the configuration file, use: &prompt.root; iscsictl -Aa To make the initiator automatically connect to all targets in /etc/iscsi.conf, add the following to /etc/rc.conf: iscsictl_enable="YES" iscsictl_flags="-Aa"