Index: head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml (revision 54367) +++ head/en_US.ISO8859-1/books/handbook/network-servers/chapter.xml (revision 54368) @@ -1,4713 +1,4713 @@ 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 behavior. 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. /usr/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" +mountd_enable="YES" 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.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. Information about this format from other sources can be useful, like 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:/usr/sbin/nologin operator:*:2:5::0:0:System &:/:/usr/sbin/nologin bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/usr/sbin/nologin tty:*:4:65533::0:0:Tty Sandbox:/:/usr/sbin/nologin kmem:*:5:65533::0:0:KMem Sandbox:/:/usr/sbin/nologin games:*:7:13::0:0:Games pseudo-user:/usr/games:/usr/sbin/nologin news:*:8:8::0:0:News Subsystem:/:/usr/sbin/nologin man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/usr/sbin/nologin bind:*:53:53::0:0:Bind Sandbox:/:/usr/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:/usr/sbin/nologin pop:*:68:6::0:0:Post Office Owner:/nonexistent:/usr/sbin/nologin nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/usr/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: +:::::::::/usr/sbin/nologin This line configures the client to import all entries but to replace the shell in those entries with /usr/sbin/nologin. Make sure that extra line is placed after +@IT_EMP:::::::::. Otherwise, all user accounts imported from NIS will have /usr/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::::::::: +:::::::::/usr/sbin/nologin The corresponding lines for the workstations would be: +@IT_EMP::::::::: +@USERS::::::::: +:::::::::/usr/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 /usr/sbin/nologin as shell. It is recommended to use the ALL-CAPS version of the hostname as the name of the netgroup: +@BOXNAME::::::::: +:::::::::/usr/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 Originally contributed by Rocky Hotas Updates 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 net/openldap-server package or port: &prompt.root; pkg install openldap-server There is a large set of default options enabled in the package. Review them by running pkg info openldap-server. If they are not sufficient (for example if SQL support is needed), please consider recompiling the port using the appropriate framework. The installation creates the directory /var/db/openldap-data to hold the data. The directory to store the certificates must be created: &prompt.root; mkdir /usr/local/etc/openldap/private 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. More detailed information about certificates and their parameters can be found in . 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. The Certificate Signing Request must be signed with the Certificate Authority in order to be used as a valid certificate: &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. The daemon running the OpenLDAP server is slapd. Its configuration is performed through slapd.ldif: the old slapd.conf has been deprecated by OpenLDAP. Configuration examples for slapd.ldif are available and can also be found in /usr/local/etc/openldap/slapd.ldif.sample. Options are documented in slapd-config(5). Each section of slapd.ldif, like all the other LDAP attribute sets, is uniquely identified through a DN. Be sure that no blank lines are left between the dn: statement and the desired end of the section. In the following example, TLS will be used to implement a secure channel. The first section represents the global configuration: # # See slapd-config(5) for details on configuration options. # This file should NOT be world readable. # dn: cn=config objectClass: olcGlobal cn: config # # # Define global ACLs to disable default read access. # olcArgsFile: /var/run/openldap/slapd.args olcPidFile: /var/run/openldap/slapd.pid olcTLSCertificateFile: /usr/local/etc/openldap/server.crt olcTLSCertificateKeyFile: /usr/local/etc/openldap/private/server.key olcTLSCACertificateFile: /usr/local/etc/openldap/ca.crt #olcTLSCipherSuite: HIGH olcTLSProtocolMin: 3.1 olcTLSVerifyClient: never The Certificate Authority, server certificate and server private key files must be specified here. It is recommended to let the clients choose the security cipher and omit option olcTLSCipherSuite (incompatible with TLS clients other than openssl). Option olcTLSProtocolMin lets the server require a minimum security level: it is recommended. While verification is mandatory for the server, it is not for the client: olcTLSVerifyClient: never. The second section is about the backend modules and can be configured as follows: # # Load dynamic backend modules: # dn: cn=module,cn=config objectClass: olcModuleList cn: module olcModulepath: /usr/local/libexec/openldap olcModuleload: back_mdb.la #olcModuleload: back_bdb.la #olcModuleload: back_hdb.la #olcModuleload: back_ldap.la #olcModuleload: back_passwd.la #olcModuleload: back_shell.la The third section is devoted to load the needed ldif schemas to be used by the databases: they are essential. dn: cn=schema,cn=config objectClass: olcSchemaConfig cn: schema include: file:///usr/local/etc/openldap/schema/core.ldif include: file:///usr/local/etc/openldap/schema/cosine.ldif include: file:///usr/local/etc/openldap/schema/inetorgperson.ldif include: file:///usr/local/etc/openldap/schema/nis.ldif Next, the frontend configuration section: # Frontend settings # dn: olcDatabase={-1}frontend,cn=config objectClass: olcDatabaseConfig objectClass: olcFrontendConfig olcDatabase: {-1}frontend olcAccess: to * by * read # # Sample global access control policy: # Root DSE: allow anyone to read it # Subschema (sub)entry DSE: allow anyone to read it # Other DSEs: # Allow self write access # Allow authenticated users read access # Allow anonymous users to authenticate # #olcAccess: to dn.base="" by * read #olcAccess: to dn.base="cn=Subschema" by * read #olcAccess: to * # by self write # by users read # by anonymous auth # # if no access controls are present, the default policy # allows anyone and everyone to read anything but restricts # updates to rootdn. (e.g., "access to * by * read") # # rootdn can always read and write EVERYTHING! # olcPasswordHash: {SSHA} # {SSHA} is already the default for olcPasswordHash Another section is devoted to the configuration backend, the only way to later access the OpenLDAP server configuration is as a global super-user. dn: olcDatabase={0}config,cn=config objectClass: olcDatabaseConfig olcDatabase: {0}config olcAccess: to * by * none olcRootPW: {SSHA}iae+lrQZILpiUdf16Z9KmDmSwT77Dj4U The default administrator username is cn=config. Type slappasswd in a shell, choose a password and use its hash in olcRootPW. If this option is not specified now, before slapd.ldif is imported, no one will be later able to modify the global configuration section. The last section is about the database backend: ####################################################################### # LMDB database definitions ####################################################################### # dn: olcDatabase=mdb,cn=config objectClass: olcDatabaseConfig objectClass: olcMdbConfig olcDatabase: mdb olcDbMaxSize: 1073741824 olcSuffix: dc=domain,dc=example olcRootDN: cn=mdbadmin,dc=domain,dc=example # Cleartext passwords, especially for the rootdn, should # be avoided. See slappasswd(8) and slapd-config(5) for details. # Use of strong authentication encouraged. olcRootPW: {SSHA}X2wHvIWDk6G76CQyCMS1vDCvtICWgn0+ # The database directory MUST exist prior to running slapd AND # should only be accessible by the slapd and slap tools. # Mode 700 recommended. olcDbDirectory: /var/db/openldap-data # Indices to maintain olcDbIndex: objectClass eq This database hosts the actual contents of the LDAP directory. Types other than mdb are available. Its super-user, not to be confused with the global one, is configured here: a (possibly custom) username in olcRootDN and the password hash in olcRootPW; slappasswd can be used as before. This repository contains four examples of slapd.ldif. To convert an existing slapd.conf into slapd.ldif, refer to this page (please note that this may introduce some unuseful options). When the configuration is completed, slapd.ldif must be placed in an empty directory. It is recommended to create it as: &prompt.root; mkdir /usr/local/etc/openldap/slapd.d/ Import the configuration database: &prompt.root; /usr/local/sbin/slapadd -n0 -F /usr/local/etc/openldap/slapd.d/ -l /usr/local/etc/openldap/slapd.ldif Start the slapd daemon: &prompt.root; /usr/local/libexec/slapd -F /usr/local/etc/openldap/slapd.d/ Option -d can be used for debugging, as specified in slapd(8). To verify that the server is running and working: &prompt.root; ldapsearch -x -b '' -s base '(objectclass=*)' namingContexts # extended LDIF # # LDAPv3 # base <> with scope baseObject # filter: (objectclass=*) # requesting: namingContexts # # dn: namingContexts: dc=domain,dc=example # search result search: 2 result: 0 Success # numResponses: 2 # numEntries: 1 The server must still be trusted. If that has never been done before, follow these instructions. Install the OpenSSL package or port: &prompt.root; pkg install openssl From the directory where ca.crt is stored (in this example, /usr/local/etc/openldap), run: &prompt.root; c_rehash . Both the CA and the server certificate are now correctly recognized in their respective roles. To verify this, run this command from the server.crt directory: &prompt.root; openssl verify -verbose -CApath . server.crt If slapd was running, restart it. As stated in /usr/local/etc/rc.d/slapd, to properly run slapd at boot the following lines must be added to /etc/rc.conf: lapd_enable="YES" slapd_flags='-h "ldapi://%2fvar%2frun%2fopenldap%2fldapi/ ldap://0.0.0.0/"' slapd_sockets="/var/run/openldap/ldapi" slapd_cn_config="YES" slapd does not provide debugging at boot. Check /var/log/debug.log, dmesg -a and /var/log/messages for this purpose. The following example adds the group team and the user john to the domain.example LDAP database, which is still empty. First, create the file domain.ldif: &prompt.root; cat domain.ldif dn: dc=domain,dc=example objectClass: dcObject objectClass: organization o: domain.example dc: domain dn: ou=groups,dc=domain,dc=example objectClass: top objectClass: organizationalunit ou: groups dn: ou=users,dc=domain,dc=example objectClass: top objectClass: organizationalunit ou: users dn: cn=team,ou=groups,dc=domain,dc=example objectClass: top objectClass: posixGroup cn: team gidNumber: 10001 dn: uid=john,ou=users,dc=domain,dc=example objectClass: top objectClass: account objectClass: posixAccount objectClass: shadowAccount cn: John McUser uid: john uidNumber: 10001 gidNumber: 10001 homeDirectory: /home/john/ loginShell: /usr/bin/bash userPassword: secret See the OpenLDAP documentation for more details. Use slappasswd to replace the plain text password secret with a hash in userPassword. The path specified as loginShell must exist in all the systems where john is allowed to login. Finally, use the mdb administrator to modify the database: &prompt.root; ldapadd -W -D "cn=mdbadmin,dc=domain,dc=example" -f domain.ldif Modifications to the global configuration section can only be performed by the global super-user. For example, assume that the option olcTLSCipherSuite: HIGH:MEDIUM:SSLv3 was initially specified and must now be deleted. First, create a file that contains the following: &prompt.root; cat global_mod dn: cn=config changetype: modify delete: olcTLSCipherSuite Then, apply the modifications: &prompt.root; ldapmodify -f global_mod -x -D "cn=config" -W When asked, provide the password chosen in the configuration backend section. The username is not required: here, cn=config represents the DN of the database section to be modified. Alternatively, use ldapmodify to delete a single line of the database, ldapdelete to delete a whole entry. If something goes wrong, or if the global super-user cannot access the configuration backend, it is possible to delete and re-write the whole configuration: &prompt.root; rm -rf /usr/local/etc/openldap/slapd.d/ slapd.ldif can then be edited and imported again. Please, follow this procedure only when no other solution is available. This is the configuration of the server only. The same machine can also host an LDAP client, with its own separate configuration. 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-dhcp43-server package or port. DHCP server DHCP installation The installation of net/isc-dhcp43-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-dhcp43-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. 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. 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 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 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_php56 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_php56 is limited. Additional support can be installed using the lang/php56-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/php56-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 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://guides.rubyonrails.org 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 cannot 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/samba410 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 by installing the same net/samba410 port or package. 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. Server Configuration Samba is configured in /usr/local/etc/smb4.conf. This file must be created before Samba can be used. A simple smb4.conf to share directories and printers with &windows; clients in a workgroup is shown here. For more complex setups involving LDAP or Active Directory, it is easier to use &man.samba-tool.8; to create the initial smb4.conf. [global] workgroup = WORKGROUP server string = Samba Server Version %v netbios name = ExampleMachine wins support = Yes security = user passdb backend = tdbsam # Example: share /usr/src accessible only to 'developer' user [src] path = /usr/src valid users = developer writable = yes browsable = yes read only = no guest ok = no public = no create mask = 0666 directory mask = 0755 Global Settings Settings that describe the network are added in /usr/local/etc/smb4.conf: workgroup The name of the workgroup to be served. 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. wins support Whether Samba will act as a WINS server. Do not enable support for WINS on more than one server on the network. Security Settings The most important settings in /usr/local/etc/smb4.conf are the security model and the backend password format. These directives control the options: security The most common settings 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 recommended authentication method, tdbsam, is ideal for simple networks and is covered here. For larger or more complex networks, ldapsam is recommended. smbpasswd was the former default and is now obsolete. <application>Samba</application> Users &os; user accounts must be mapped to the SambaSAMAccount database for &windows; clients to access the share. Map existing &os; user accounts using &man.pdbedit.8;: &prompt.root; pdbedit -a username This section has only mentioned the most commonly used settings. Refer to the Official Samba Wiki 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_server_enable="YES" To start Samba now: &prompt.root; service samba_server start Performing sanity check on Samba configuration: OK 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 is also required, set: winbindd_enable="YES" Samba can be stopped at any time by typing: &prompt.root; service samba_server 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 https://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 to synchronize the clock on that machine or to provide time services to other computers in the network. 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 On &os;, the built-in ntpd can be used to synchronize a system's clock. Ntpd is configured using &man.rc.conf.5; variables and /etc/ntp.conf, as detailed in the following sections. Ntpd communicates with its network peers using UDP packets. Any firewalls between your machine and its NTP peers must be configured to allow UDP packets in and out on port 123. The <filename>/etc/ntp.conf</filename> file NTP ntp.conf Ntpd reads /etc/ntp.conf to determine which NTP servers to query. 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. The servers which are queried can be local to the network, provided by an ISP, or selected from an online list of publicly accessible NTP servers. When choosing a public NTP server, select one that is geographically close and review its usage policy. The pool configuration keyword selects one or more servers from a pool of servers. An online list of publicly accessible NTP pools is available, organized by geographic area. In addition, &os; provides a project-sponsored pool, 0.freebsd.pool.ntp.org. Sample <filename>/etc/ntp.conf</filename> This is a simple example of an ntp.conf file. It can safely be used as-is; it contains the recommended restrict options for operation on a publicly-accessible network connection. # Disallow ntpq control/query access. Allow peers to be added only # based on pool and server statements in this file. restrict default limited kod nomodify notrap noquery nopeer restrict source limited kod nomodify notrap noquery # Allow unrestricted access from localhost for queries and control. restrict 127.0.0.1 restrict ::1 # Add a specific server. server ntplocal.example.com iburst # Add FreeBSD pool servers until 3-6 good servers are available. tos minclock 3 maxclock 6 pool 0.freebsd.pool.ntp.org iburst # Use a local leap-seconds file. leapfile "/var/db/ntpd.leap-seconds.list" The format of this file is described in &man.ntp.conf.5;. The descriptions below provide a quick overview of just the keywords used in the sample file above. By default, an NTP server is accessible to any network host. The restrict keyword controls which systems can access the server. Multiple restrict entries are supported, each one refining the restrictions given in previous statements. The values shown in the example grant the local system full query and control access, while allowing remote systems only the ability to query the time. For more details, refer to the Access Control Support subsection of &man.ntp.conf.5;. The server keyword specifies a single server to query. The file can contain multiple server keywords, with one server listed on each line. The pool keyword specifies a pool of servers. Ntpd will add one or more servers from this pool as needed to reach the number of peers specified using the tos minclock value. The iburst keyword directs ntpd to perform a burst of eight quick packet exchanges with a server when contact is first established, to help quickly synchronize system time. The leapfile keyword specifies the location of a file containing information about leap seconds. The file is updated automatically by &man.periodic.8;. The file location specified by this keyword must match the location set in the ntp_db_leapfile variable in /etc/rc.conf. NTP entries in <filename>/etc/rc.conf</filename> NTP rc.conf Set ntpd_enable=YES to start ntpd at boot time. Once ntpd_enable=YES has been added to /etc/rc.conf, ntpd can be started immediately without rebooting the system by typing: &prompt.root; service ntpd start Only ntpd_enable must be set to use ntpd. The rc.conf variables listed below may also be set as needed. Set ntpd_sync_on_start=YES to allow ntpd to step the clock any amount, one time at startup. Normally ntpd will log an error message and exit if the clock is off by more than 1000 seconds. This option is especially useful on systems without a battery-backed realtime clock. Set ntpd_oomprotect=YES to protect the ntpd daemon from being killed by the system attempting to recover from an Out Of Memory (OOM) condition. Set ntpd_config= to the location of an alternate ntp.conf file. Set ntpd_flags= to contain any other ntpd flags as needed, but avoid using these flags which are managed internally by /etc/rc.d/ntpd: -p (pid file location) -c (set ntpd_config= instead) <application>Ntpd</application> and the unpriveleged <literal>ntpd</literal> user Ntpd on &os; can start and run as an unpriveleged user. Doing so requires the &man.mac.ntpd.4; policy module. The /etc/rc.d/ntpd startup script first examines the NTP configuration. If possible, it loads the mac_ntpd module, then starts ntpd as unpriveleged user ntpd (user id 123). To avoid problems with file and directory access, the startup script will not automatically start ntpd as ntpd when the configuration contains any file-related options. The presence of any of the following in ntpd_flags requires manual configuration as described below to run as the ntpd user: -f or --driftfile -i or --jaildir -k or --keyfile -l or --logfile -s or --statsdir The presence of any of the following keywords in ntp.conf requires manual configuration as described below to run as the ntpd user: crypto driftfile key logdir statsdir To manually configure ntpd to run as user ntpd you must: Ensure that the ntpd user has access to all the files and directories specified in the configuration. Arrange for the mac_ntpd module to be loaded or compiled into the kernel. See &man.mac.ntpd.4; for details. Set ntpd_user="ntpd" in /etc/rc.conf 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. &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 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"