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The Linux NIS(YP)/NYS/NIS+ HOWTO Thorsten Kukuk v0.9, 10. January 1998 This document describes how to configure Linux as NIS(YP) or NIS+ client and how to install as NIS server. 1. Introduction More and more, Linux machines are installed as part of a network of computers. To simplify network administration, most networks (mostly Sun-based networks) run the Network Information Service. Linux machines can take full advantage of existing NIS service or provide NIS service themselves. Linux machines can also act as full NIS+ clients, this support is in beta stage. This document tries to answer questions about setting up NIS(YP) and NIS+ on your Linux machine. Don't forget to read the section about ``the RPC Portmapper'' The NIS-Howto is edited and maintained by: Thorsten Kukuk, kukuk@vt.uni-paderborn.de The primary source of the information for the initial NIS-Howto was from: Andrea Dell'Amico <adellam@ZIA.ms.it> Mitchum DSouza <Mitch.DSouza@NetComm.IE> Erwin Embsen <erwin@nioz.nl> Peter Eriksson <peter@ifm.liu.se> who we should thank for writing the first versions of this document. 1.1. New versions of this document New versions of this document will be posted periodically to the newsgroups comp.os.linux.help <news:comp.os.linux.help> and comp.os.linux.announce <news:comp.os.linux.announce>. They will also be uploaded to various Linux WWW and FTP sites, including the LDP home page. You can always view the latest version of this on the World Wide Web via the URL http://sunsite.unc.edu/mdw/HOWTO/NIS-HOWTO.html <http://sunsite.unc.edu/mdw/HOWTO/NIS-HOWTO.html>. 1.2. Disclaimer Although this document has been put together to the best of our knowledge it may, and probably does contain errors. Please read any README files that are bundled with any of the various pieces of software described in this document for more detailed and accurate information. We will attempt to keep this document as error free as possible. 1.3. Feedback and Corrections If you have questions or comments about this document, please feel free to mail Thorsten Kukuk, at kukuk@vt.uni-paderborn.de. I welcome any suggestions or criticisms. If you find a mistake with this document, please let me know so I can correct it in the next version. Thanks. Please do not mail me questions about special problems with your Linux distributions! I don't know every Linux Distribution. But I will try to add every solution you send me. 1.4. Acknowledgements We would like to thank all the people who have contributed (directly or indirectly) to this document. In alphabetical order: Byron A Jeff <byron@cc.gatech.edu> Miquel van Smoorenburg <miquels@cistron.nl> Theo de Raadt <deraadt@theos.com> is responsible for the original yp- clients code. Swen Thuemmler <swen@uni-paderborn.de> ported the yp- clients code to Linux and also ported the yp-routines in libc (again based on Theo's work). Thorsten Kukuk has written the NIS(YP) and NIS+ routines for GNU libc 2.x from scratch. 2. Glossary and General Information 2.1. Glossary of Terms In this document a lot of acronyms are used. Here are the most important acronyms and a brief explanation: DBM DataBase Management, a library of functions which maintain key- content pairs in a data base. DLL Dynamically Linked Library, a library linked to an executable program at run-time. domainname A name "key" that is used by NIS clients to be able to locate a suitable NIS server that serves that domainname key. Please note that this does not necessarily have anything at all to do with the DNS "domain" (machine name) of the machine(s). FTP File Transfer Protocol, a protocol used to transfer files between two computers. libnsl Name services library, a library of name service calls (getpwnam, getservbyname, etc...) on SVR4 Unixes. GNU libc uses this for the NIS (YP) and NIS+ functions. libsocket Socket services library, a library for the socket service calls (socket, bind, listen, etc...) on SVR4 Unixes. NIS Network Information Service, a service that provides information, that has to be known throughout the network, to all machines on the network. There is support for NIS in Linux's standard libc library, which in the following text is referred to as "traditional NIS". NIS+ Network Information Service (Plus :-), essentially NIS on steroids. NIS+ is designed by Sun Microsystems Inc. as a replacement for NIS with better security and better handling of _large_ installations. NYS This is the name of a project and stands for NIS+, YP and Switch and is managed by Peter Eriksson <peter@ifm.liu.se>. It contains among other things a complete reimplementation of the NIS (= YP) code that uses the Name Services Switch functionality of the NYS library. NSS Name Service Switch. The /etc/nsswitch.conf file determines the order of lookups performed when a certain piece of information is requested. RPC Remote Procedure Call. RPC routines allow C programs to make procedure calls on other machines across the network. When people talk about RPC they most often mean the Sun RPC variant. YP Yellow Pages(tm), a registered trademark in the UK of British Telecom plc. TCP-IP Transmission Control Protocol/Internet Protocol. It's the data communication protocol most often used on Unix machines. 2.2. Some General Information The next four lines are quoted from the Sun(tm) System & Network Administration Manual: "NIS was formerly known as Sun Yellow Pages (YP) but the name Yellow Pages(tm) is a registered trademark in the United Kingdom of British Telecom plc and may not be used without permission." NIS stands for Network Information Service. Its purpose is to provide information, that has to be known throughout the network, to all machines on the network. Information likely to be distributed by NIS is: ╖ login names/passwords/home directories (/etc/passwd) ╖ group information (/etc/group) So, for example, if your password entry is recorded in the NIS passwd database, you will be able to login on all machines on the net which have the NIS client programs running. Sun is a trademark of Sun Microsystems, Inc. licensed to SunSoft, Inc. 3. NIS or NIS+ ? The choice between NIS and NIS+ is easy - use NIS if you don't have to use NIS+ or have severe security needs. NIS+ is _much_ more problematic to administer (it's pretty easy to handle on the client side, but the server side is horrible). Another problem is that the support for NIS+ under Linux is still under developement - you need the latest glibc snapshot for it or have to wait for glibc 2.1. There is a port of the glibc NIS+ support for libc5 as drop in replacement. 3.1. libc 4/5 with traditional NIS or NYS ? The choice between "traditional NIS" or the NIS code in the NYS library is a choice between laziness and maturity vs. flexibility and love of adventure. The "traditional NIS" code is in the standard C library and has been around longer and sometimes suffers from it's age and slight inflexibility. The NIS code in the NYS library requires you to recompile the libc library to include the NYS code into the libc library (or maybe you can go get a precompiled version of libc from someone who has already done it). Another difference is that the traditional NIS code has some support for NIS Netgroups, which the NYS code doesn't (yet). On the other hand the NYS code allows you to handle Shadow Passwords in a transparent way. The "traditonal NIS" code doesn't support Shadow Passwords over NIS. Forgot this all if you use the new GNU C Library 2.x (aka libc6). It supports NSS (name switch service), which makes it very flexible, and contains support for the following NIS/NIS+ maps: aliases, ethers, group, hosts, netgroups, networks, protocols, publickey, passwd, rpc, services and shadow. 4. How it works 4.1. How NIS(YP) works Within a network there must be at least one machine acting as a NIS server. You can have multiple NIS servers, each serving different NIS "domains" - or you can have cooperating NIS servers, where one is said to be the master NIS server, and all the other are so-called slave NIS servers (for a certain NIS "domain", that is!) - or you can have a mix of them... Slave servers only have copies of the NIS databases and receive these copies from the master NIS server whenever changes are made to the master's databases. Depending on the number of machines in your network and the reliability of your network, you might decide to install one or more slave servers. Whenever a NIS server goes down or is too slow in responding to requests, a NIS client connected to that server will try to find one that is up or quicker. NIS databases are in so-called DBM format, derived from ASCII databases. For example, the files /etc/passwd and /etc/group can be directly converted to DBM format using ASCII-to-DBM translation software ("makedbm", it's included with the server software). The master NIS server should have both, the ASCII databases and the DBM databases. Slave servers will be notified of any change to the NIS maps, (via the "yppush" program), and automatically retrieve the necessary changes in order to synchronize their databases. NIS clients do not need to do this since they always talk to the NIS server to read the information stored in it's DBM databases. The author of the YP clients for linux has informed us that the newest ypbind (ypbind-3.3.tar.gz) is able to get the server from a configuration file - thus no need to broadcast (which is insecure - due to the fact that anyone may install a NIS server and answer the broadcast queries...) 4.2. How NIS+ works NIS+ is a new version of the network information nameservice from Sun. The biggest difference between NIS and NIS+ is, that NIS+ has support for data encryption and authentication over secure RPC. The naming model of NIS+ is based upon a tree structure. Each node in the tree corresponds to an NIS+ object, from which we have six types: directory, entry, group, link, table and private. The NIS+ directory that forms the root of the NIS+ namespace is called the root directory. There are two special NIS+ directories: org_dir and groups_dir. The org_dir directory consists of all administration tables, such as passwd, hosts, and mail_aliases. The groups_dir directory consists of NIS+ group objects which are used for access control. The collection of org_dir, groups_dir and their parent directory is referred to as an NIS+ domain. 5. The RPC Portmapper To run any of the software mentioned below you will need to run the program /usr/sbin/portmap. Some Linux distributions already have the code in the /etc/rc.d/ files to start up this daemon. All you have to do is to activate it and reboot your Linux machine. Read your Linux Distribution Documentation how to do this. The RPC portmapper (portmap(8)) is a server that converts RPC program numbers into TCP/IP (or UDP/IP) protocol port numbers. It must be running in order to make RPC calls (which is what the NIS/NIS+ client software does) to RPC servers (like a NIS or NIS+ server) on that machine. When an RPC server is started, it will tell portmap what port number it is listening to, and what RPC program numbers it is prepared to serve. When a client wishes to make an RPC call to a given program number, it will first contact portmap on the server machine to determine the port number where RPC packets should be sent. Normally, standard RPC servers are started by inetd(8), so portmap must be started before inetd is invoked. For secure RPC, the portmapper needs the Time Service. Make sure, that the Time Service is enabled in /etc/inetd.conf on all hosts: # # Time service is used for clock syncronization. # time stream tcp nowait nobody /usr/sbin/tcpd in.timed time dgram udp wait nobody /usr/sbin/tcpd in.timed IMPORTANT: Don't forget to restart inetd after changes on this file ! 6. What do you need to set up NIS? 6.1. Determine whether you are a Server, Slave or Client. To answer this question you have to consider two cases: 1. Your machine is going to be part of a network with existing NIS servers 2. You do not have any NIS servers in the network yet In the first case, you only need the client programs (ypbind, ypwhich, ypcat, yppoll, ypmatch). The most important program is ypbind. This program must be running at all times, that is, it should always appear in the list of processes. It's a so-called daemon process and needs to be started from the system's startup file (eg. /etc/rc.local, /etc/init.d/nis, /etc/rc.d/init.d/ypbind). As soon as ypbind is running, your system has become a NIS client. In the second case, if you don't have NIS servers, then you will also need a NIS server program (usually called ypserv). Section 8 describes how to set up a NIS server on your Linux machine using the "ypserv" implementation by Peter Eriksson and Thorsten Kukuk. Note that from version 0.14 this implementation supports the master-slave concept talked about in section 4.1. There is also another free NIS server available, called "yps", written by Tobias Reber in Germany which does support the master-slave concept, but has other limitations and isn't supported any longer. 6.2. The Software The system library "/usr/lib/libc.a" (version 4.4.2 and better) or the shared library "/lib/libc.so.x" contain all necessary system calls to succesfully compile the NIS client and server software. For glibc 2.x, you also need /lib/libnsl.so.1. Some people reported that NIS only works with "/usr/lib/libc.a" version 4.5.21 and better so if you want to play it safe don't use older libc's. The NIS client software can be obtained from: Site Directory File Name ftp.uni-paderborn.de /linux/local/yp yp-clients-2.2.tar.gz ftp.uni-paderborn.de /linux/local/yp ypbind-3.3.tar.gz ftp.kernel.org /pub/linux/utils/net/NIS yp-tools-1.4.tar.gz ftp.kernel.org /pub/linux/utils/net/NIS ypbind-3.3.tar.gz sunsite.unc.edu /pub/Linux/system/Network/admin yp-clients-2.2.tar.gz Once you obtained the software, please follow the instructions which come with the software. yp-clients 2.2 are for use with libc4 and libc5 until 5.4.20. libc 5.4.21 and glibc 2.x needs yp-tools 1.4. Since there was some bugs in the NIS code, you shouldn't use libc 5.4.21-5.4.35. Use libc 5.4.36 or later instead. ypbind 3.3 will work with all libraries. You should never use the ypbind from yp-clients 2.2. 6.3. The ypbind daemon Assuming you have succesfully compiled the software you are now ready to install the software. A suitable place for the ypbind daemon is the directory /usr/sbin. Some people may tell you, that you don't need ypbind on a system with NYS. This is wrong, ypwhich and ypcat need it. You'll need to do this as root of course. The other binaries (ypwhich, ypcat, yppoll, ypmatch) should go in a directory accessible by all users, normally /usr/bin. The ypbind process has a configuration file called /etc/yp.conf. You can hardcode a NIS server there - for more info see the manual page for ypbind(8). You also need this file for NYS. An example: ypserver voyager ypserver ds9 If the system could resolv the hostnames without NIS, you could use the name, else you have to use the IP address. It might be a good idea to test ypbind before incorporating it in the /etc/rc.d/ files. To test ypbind do the following: ╖ Make sure you have your domain name set. If it is not set then issue the command: /bin/domainname nis.domain where nis.domain should be some string, _NOT_ normally associated with the domain name of your machine! The reason for this is that it makes it a little harder for external crackers to retreive the password database from your NIS servers. If you don't know what the NIS domain name is on your network, ask your system/network administrator. ╖ Start up "/usr/sbin/portmap" if it is not already running. ╖ Create the directory "/var/yp" if it does not exist. ╖ Start up "/usr/sbin/ypbind" ╖ Use the command "rpcinfo -p localhost" to check if ypbind was able to register its service with the portmapper. The rpcinfo should produce something like: program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100007 2 udp 637 ypbind 100007 2 tcp 639 ypbind 300019 1 udp 660 ╖ You may also run "rpcinfo -u localhost ypbind". This command should produce something like: program 100007 version 2 ready and waiting At this point you should be able to use NIS client programs like ypcat, etc... For example, "ypcat passwd" will give you the entire NIS password database. IMPORTANT: If you skipped the test procedure then make sure you have set the domain name, and created the directory: /var/yp This directory MUST exist for ypbind to start up succesfully. If the test worked you may now want to change the files in /etc/rc.d/ on your system so that ypbind will be started up at boot time and your system will act as a NIS client. Make sure, that the domainname will be set at boot time. Well, that's it. Reboot the machine and watch the boot messages to see if ypbind is actually started. 6.4. Setting up a NIS Client using Traditional NIS For host lookups you must set (or add) "nis" to the lookup order line in your /etc/host.conf file. Please read the manpage "resolv+.8" for more details. Add the following line to /etc/passwd on your NIS clients: +:::::: You can also use the + and - characters to include/exclude or change users. If you want to exclude the user guest just add -guest to your /etc/passwd file. You want to use a different shell (e.g. ksh) for the user "linux"? No problem, just add "+linux::::::/bin/ksh" (without the quotes) to your /etc/passwd. Fields that you don't want to change have to be left empty. You could also use Netgroups for user control. For example, to only allow login-access to miquels, dth and ed, and all members of the sysadmin netgroup, but to have the account data of all other users available: +miquels::::::: +ed::::::: +dth::::::: +@sysadmins::::::: -ftp +:*::::::/etc/NoShell Note that in Linux you can also override the password field, as we did in this example. In this example, we also remove the login "ftp", so it isn't known any longer, and anonymous ftp will not work. The netgroup would be look like sysadmins (-,software,) (-,kukuk,) IMPORTANT: Note that the netgroup feature is implemented starting from libc 4.5.26. But if you have a version of libc earlier than 4.5.26, every user in the NIS password database can access your linux machine if you run "ypbind". 6.5. Setting up a NIS Client using NYS All that is required is that the NIS configuration file (/etc/yp.conf) points to the correct server(s) for its information. Also, the Name Services Switch configuration file (/etc/nsswitch.conf) must be correctly set up. You should install ypbind. It isn't needed by the libc, but the NIS(YP) tools need it. If you wish to use the include/exclude user feature (+/-guest/+@admins), you have to use "passwd: compat" and "group: compat". Note, that there is no "shadow: compat" ! You have to use "shadow: files nis" in this case. The NYS sources are part of the libc 5 sources. When run configure, say the first time "NO" to the "Values correct" question, then say "YES" to "Build a NYS libc from nys". 6.6. Setting up a NIS Client using glibc 2.x The glibc uses "traditional NIS", so you need to start ypbind. The Name Services Switch configuration file (/etc/nsswitch.conf) must be correctly set up. If you use the compat mode for passwd, shadow or group, you have to add the "+" at the end of this files, and you could use the include/exclude user feature. The configuration is excatly the same as under Solaris 2.x. 6.7. The nsswitch.conf File The Network Services switch file /etc/nsswitch.conf determines the order of lookups performed when a certain piece of information is requested, just like the /etc/host.conf file which determines the way host lookups are performed. For example, the line hosts: files nis dns specifies that host lookup functions should first look in the local /etc/hosts file, followed by a NIS lookup and finally thru the domain name service (/etc/resolv.conf and named), at which point if no match is found an error is returned. A first version of a manual page for nsswitch.conf could be found at http://www-vt.uni-paderborn.de/~kukuk/linux/misc.html <http://www- vt.uni-paderborn.de/~kukuk/linux/misc.html>. A good /etc/nsswitch.conf file for NIS is: # # /etc/nsswitch.conf # # An example Name Service Switch config file. This file should be # sorted with the most-used services at the beginning. # # The entry '[NOTFOUND=return]' means that the search for an # entry should stop if the search in the previous entry turned # up nothing. Note that if the search failed due to some other reason # (like no NIS server responding) then the search continues with the # next entry. # # Legal entries are: # # nisplus Use NIS+ (NIS version 3) # nis Use NIS (NIS version 2), also called YP # dns Use DNS (Domain Name Service) # files Use the local files # db Use the /var/db databases # [NOTFOUND=return] Stop searching if not found so far # passwd: compat group: compat shadow: compat passwd_compat: nis group_compat: nis shadow_compat: nis hosts: nis files dns services: nis [NOTFOUND=return] files networks: nis [NOTFOUND=return] files protocols: nis [NOTFOUND=return] files rpc: nis [NOTFOUND=return] files ethers: nis [NOTFOUND=return] files netmasks: nis [NOTFOUND=return] files netgroup: nis bootparams: nis [NOTFOUND=return] files publickey: nis [NOTFOUND=return] files automount: files aliases: nis [NOTFOUND=return] files passwd_compat, group_compat and shadow_compat are only supported by glibc 2.x. If there are no shadow rules in /etc/nsswitch.conf, glibc will use the passwd rule for lookups. There are some more lookup module for glibc like hesoid. For more information, read the glibc documentation. 7. What do you need to set up NIS+ ? 7.1. The Software The Linux NIS+ client code was developed for the GNU C library 2. There is also a port for Linux libc5, since all commercial Applicatons are linked against this library, and you couldn't recompile them for using glibc. There are problems with libc5 + NIS+: You couldn't link static programs with it, and programs compiled with this library will not work with other libc5 versions. You need to retrieve and compile the latest GNU C library 2 snapshot. And you need a glibc based system like RedHat 5.0 or the unstable Debian. But be warned: This are all beta Software ! Read the Docs about glibc snapshots and from the Distributions ! glibc 2.0.x doesn't contain the NIS+ support, and will never contain it. The first public version with NIS+ support will be 2.1. The NIS+ client software can be obtained from: Site Directory File Name ftp.kernel.org /pub/software/libs/glibc libc-*, glibc-crypt-*, glibc-linuxthreads-* ftp.kernel.org /pub/linux/utils/net/NIS+ nis-tools-1.4.tar.gz ftp.kernel.org /pub/linux/utils/net/NIS+ pam_keylogin-1.1.tar.gz Distributions based on glibc can be fetched from: Site Directory ftp.redhat.com /pub/redaht/mustang ftp.debian.org /pub/debian/hamm For compilation of the GNU C Library, please follow the instructions which come with the software. Here you could find the patched libc5, based on NYS and the glibc sources as drop in replacement for the standart libc5: Site Directory File Name ftp.kernel.org /pub/linux/utils/net/NIS+ libc-5.4.38-nsl-0.4.6.tar.gz You should also look at http://www-vt.uni- paderborn.de/~kukuk/linux/nisplus.html <http://www-vt.uni- paderborn.de/~kukuk/linux/nisplus.html> for more information and the latest sources. 7.2. Setting up a NIS+ client IMPORTANT: For setting up a NIS+ client, read your Solaris NIS+ docs what to do on the server side ! This document only describes what to do on the client side ! After installing the new libc and nis-tools, create the credentials for the new client on the NIS+ server. Then run domainname nisplus.domain. nisinit -c -H <NIS+ server> to initialize the cold Start File. Read the nisinit man page for more options. Make sure, that the domainname will always be set after a reboot. If you don't know what the NIS+ domain name is on your network, ask your system/network administrator. Now you should change your /etc/nsswitch.conf file. Make sure, that the only service after publickey is nisplus ("publickey: nisplus"), and nothing else ! After this, start keyserv and make sure, that it will always be started at boot time. Run keylogin -r to store the root secretkey on your system. (I hope you have added the publickey for the new host on the NIS+ Server ?). "niscat passwd.org_dir" should now show you all entries in the passwd database. 7.3. NIS+, keylogin, login and PAM When the user logs in, he need to set his secretkey to keyserv. This is done by calling "keylogin". The login from the shadow package will do this for the user. For a PAM aware login, you have to install pam_keylogin-1.1.tar.gz and change the /etc/pam.d/login file to use pam_unix_auth, not pwdb, which doesn't support NIS+. An example: #%PAM-1.0 auth required /lib/security/pam_securetty.so auth required /lib/security/pam_keylogin.so auth required /lib/security/pam_unix_auth.so auth required /lib/security/pam_nologin.so account required /lib/security/pam_unix_acct.so password required /lib/security/pam_unix_passwd.so session required /lib/security/pam_unix_session.so 7.4. The nsswitch.conf File The Network Services switch file /etc/nsswitch.conf determines the order of lookups performed when a certain piece of information is requested, just like the /etc/host.conf file which determines the way host lookups are performed. For example, the line hosts: files nisplus dns specifies that host lookup functions should first look in the local /etc/hosts file, followed by a NIS+ lookup and finally thru the domain name service (/etc/resolv.conf and named), at which point if no match is found an error is returned. A first version of a manual page for nsswitch.conf could be found at http://www-vt.uni-paderborn.de/~kukuk/linux/misc.html <http://www- vt.uni-paderborn.de/~kukuk/linux/misc.html>. A good /etc/nsswitch.conf file for NIS+ is: # # /etc/nsswitch.conf # # An example Name Service Switch config file. This file should be # sorted with the most-used services at the beginning. # # The entry '[NOTFOUND=return]' means that the search for an # entry should stop if the search in the previous entry turned # up nothing. Note that if the search failed due to some other reason # (like no NIS server responding) then the search continues with the # next entry. # # Legal entries are: # # nisplus Use NIS+ (NIS version 3) # nis Use NIS (NIS version 2), also called YP # dns Use DNS (Domain Name Service) # files Use the local files # db Use the /var/db databases # [NOTFOUND=return] Stop searching if not found so far # passwd: compat # for libc5: passwd: files nisplus group: compat # for libc5: group: files nisplus shadow: compat # for libc5: shadow: files nisplus passwd_compat: nisplus group_compat: nisplus shadow_compat: nisplus hosts: nisplus files dns services: nisplus [NOTFOUND=return] files networks: nisplus [NOTFOUND=return] files protocols: nisplus [NOTFOUND=return] files rpc: nisplus [NOTFOUND=return] files ethers: nisplus [NOTFOUND=return] files netmasks: nisplus [NOTFOUND=return] files netgroup: nisplus bootparams: nisplus [NOTFOUND=return] files publickey: nisplus automount: files aliases: nisplus [NOTFOUND=return] files 8. Setting up a NIS Server 8.1. The Server Program ypserv This document only describes how to set up the "ypserv" NIS server. The NIS server software can be found on: Site Directory File Name ftp.kernel.org /pub/linux/utils/net/NIS ypserv-1.2.7.tar.gz waaug.erols.com /pub/net/nis ypserv-1.2.7.tar.gz You could also look at http://www-vt.uni- paderborn.de/~kukuk/linux/nis.html <http://www-vt.uni- paderborn.de/~kukuk/linux/nis.html> for more information and the latest sources. The server setup is the same for both traditional NIS and NYS. Compile the software to generate the "ypserv" and "makedbm" programs. If you run your server as master, determine what files you require to be available via NIS and then add or remove the appropriate entries to the /var/yp/Makefile. Now edit /var/yp/securenets and /etc/ypserv.conf. For more information, read the ypserv(8) and ypserv.conf(5) manual pages. Make sure the portmapper (portmap(8)) is running, and start the server "ypserv". The command % rpcinfo -u localhost ypserv should output something like program 100004 version 2 ready and waiting Now generate the NIS (YP) database. On the master, run % /usr/lib/yp/ypinit -m on a slave, make sure that ypwhich -m works. Then run % /usr/lib/yp/ypinit -s masterhost That's it, your server is up and running. You might want to edit root's crontab *on the slave* server and add the following lines: 20 * * * * /usr/lib/yp/ypxfr_1perhour 40 6 * * * /usr/lib/yp/ypxfr_1perday 55 6,18 * * * /usr/lib/yp/ypxfr_2perday This will ensure that most NIS maps are kept up-to-date, even if an update is missed because the slave was down at the time the update was done on the master. If you want to restrict access to your NIS server, you'll have to setup the NIS server as a client as well by running ypbind and adding the plus-entries to /etc/passwd _halfway_ the password file. The library functions will ignore all normal entries after the first NIS entry, and will get the rest of the info through NIS. This way the NIS access rules are maintained. example: root:x:0:0:root:/root:/bin/bash daemon:*:1:1:daemon:/usr/sbin: bin:*:2:2:bin:/bin: sys:*:3:3:sys:/dev: sync:*:4:100:sync:/bin:/bin/sync games:*:5:100:games:/usr/games: man:*:6:100:man:/var/catman: lp:*:7:7:lp:/var/spool/lpd: mail:*:8:8:mail:/var/spool/mail: news:*:9:9:news:/var/spool/news: uucp:*:10:50:uucp:/var/spool/uucp: nobody:*:65534:65534:noone at all,,,,:/dev/null: +miquels:::::: +:*:::::/etc/NoShell [ All normal users AFTER this line! ] tester:*:299:10:Just a test account:/tmp: miquels:1234567890123:101:10:Miquel van Smoorenburg:/home/miquels:/bin/zsh The user tester will exist, but have a shell of /etc/NoShell. miquels will have normal access. Alternatively, you could edit the /var/yp/Makefile file and set NIS to use another source password file. On big systems, the NIS password and group files are usually stored in /var/yp/ypfiles/. If you do this the normal tools to administrate the password file such as "passwd", "chfn", "adduser" will not work anymore and you will need special homemade tools for this. However yppasswd, ypchsh and ypchfn will work ofcourse. 8.2. The Server Program yps To set up the "yps" NIS server please refer to the previous paragraph. The "yps" server setup is similar, _but_ not exactly the same so beware if you try to apply the "ypserv" instructions to "yps"! "yps" is not supported by any author, and contains some security leaks. You shouldn't really use it ! The "yps" NIS server software can be found on: Site Directory File Name ftp.kernel.org /pub/linux/utils/net/NIS yps-0.21.tar.gz ftp.lysator.liu.se /pub/NYS/servers yps-0.21.tar.gz 8.3. The Program rpc.yppasswdd Whenever users change their passwords, the NIS password database and probably other NIS databases, which depend on the NIS password database, should be updated. The program "rpc.yppasswdd" is a server that handles password changes and makes sure that the NIS information will be updated accordingly. rpc.yppasswdd is now integrated in ypserv 1.2.7. You don't need the older, separate yppasswd-0.9.tar.gz or yppasswd-0.10.tar.gz, and you shouldn't use them any longer. The rpc.yppasswdd in ypserv 1.2.7 has full shadow support. yppasswd is now part of yp-tools-1.4.tar.gz, You need to start rpc.yppasswdd only on the NIS master server. By default, users are not allowed to change their full name or the login shell. You could allow this with the -e chfn or -e chsh option. 9. Verifying the NIS/NYS Installation If everything is fine (as it should be), you should be able to verify your installation with a few simple commands. Assuming, for example, your passwd file is being supplied by NIS, the command % ypcat passwd should give you the contents of your NIS passwd file. The command % ypmatch userid passwd (where userid is the login name of an arbitrary user) should give you the user's entry in the NIS passwd file. The "ypcat" and "ypmatch" programs should be included with your distribution of traditional NIS or NYS. If a user couldn't log in, run the following program on the client: #include <stdio.h> #include <pwd.h> #include <sys/types.h> int main(int argc, char *argv[]) { struct passwd *pwd; if(argc != 2) { fprintf(stderr,"Usage: getwpnam username\n"); exit(1); } pwd=getpwnam(argv[1]); if(pwd != NULL) { printf("name.....: [%s]\n",pwd->pw_name); printf("password.: [%s]\n",pwd->pw_passwd); printf("user id..: [%d]\n", pwd->pw_uid); printf("group id.: [%d]\n",pwd->pw_gid); printf("gecos....: [%s]\n",pwd->pw_gecos); printf("directory: [%s]\n",pwd->pw_dir); printf("shell....: [%s]\n",pwd->pw_shell); } else fprintf(stderr,"User \"%s\" not found!\n",argv[1]); exit(0); } Running this program with the username as parameter, will print all the information the getpwnam function will give back for this user. This should show you, which entry is incorrect. The most common problem is, that the password field is overwritten with a "*". 10. Common Problems and Troubleshooting NIS Here are some common problems reported by various users: 1. The libraries for 4.5.19 are broken. NIS won't work with it. 2. If you upgrade the libraries from 4.5.19 to 4.5.24 then the su command breaks. You need to get the su command from the slackware 1.2.0 distribution. Incidentally that's where you can get the updated libraries. 3. You could run into trouble with NIS and DNS on the same machine using an old a.out distribution. The DNS server occasionally will not bring up NIS. 4. When a NIS server goes down and comes up again ypbind starts complaining with messages like: yp_match: clnt_call: RPC: Unable to receive; errno = Connection refused and logins are refused for those who are registered in the NIS database. Try to login as root and if you succeed, then kill ypbind and start it up again. An update to ypbind 3.3 or higher should also help. 5. After upgrade the libc to a version greater then 5.4.20, the YP tools will not work any longer. You need yp-tools 1.2 or later for libc >= 5.4.21 and glibc 2.x and yp-clients 2.2. for earlier versions. 6. In libc 5.4.21 - 5.4.35 yp_maplist is broken, you need 5.4.36 or later for yp-tools 1.x. 7. libc 5 with traditional NIS doesn't support shadow passwords over NIS. You need libc5 + NYS or glibc 2.x. 11. Frequently Asked Questions Most of your questions should be answered by now. If there are still questions unanswered you might want to post a message to comp.os.linux.help or comp.os.linux.networking or contact one of the authors of this HOWTO.