NIS

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Network Information Service (NIS) is a protocol developed by Sun to allow one to defer user authentication to a server. The server software is in the ypservAUR package, and the client software is in the yp-toolsAUR package. ypbind-mtAUR is also available, which is a multi threaded version of the client daemon.

Note: This article somewhat unfinished. In the future that will change, but in the meantime check the More resources section.

NIS Server

Install Packages

Install the ypbind-mtAUR, ypservAUR, and yp-toolsAUR packages.

Configuration

/etc/hosts

Add your server's external (not 127.0.0.1) IP address to the hosts file. Make sure it is the first non-commented line in the file, yes, even above the localhost line, like so:

#
# /etc/hosts: static lookup table for host names
#

#<ip-address>	<hostname.domain.org>	<hostname>
#::1		localhost.localdomain	localhost
192.168.1.10   nis_server.domain.com   nis_server
127.0.0.1	localhost.localdomain	localhost nis_server
# End of file

This is due to a peculiarity in ypinit (maybe it's a bug, maybe it's a feature), which will always add the first line in /etc/hosts to the list of ypservers.

/etc/nisdomainname

Add the domain name to /etc/nisdomainname:

# NISDOMAINNAME="nis-domain-name"

/etc/ypserv.conf

Add rules to /etc/ypserv.conf for your your nis clients of this form:

# ip-address-of-client : nis-domain-name : rule : security

For example:

# 192.168. : home-domain : * : port

For more information see man ypserv.conf.

/var/yp/Makefile

Add or remove files you would like NIS to use to /var/yp/Makefile under the "all" rule.

Default:

# all:  passwd group hosts rpc services netid protocols netgrp \
#         shadow # publickey networks ethers bootparams printcap mail \
#         # amd.home auto.master auto.home auto.local passwd.adjunct \
#         # timezone locale netmasks

After that you have to build your NIS database:

# cd /var/yp
# make

Or you can do it in a more automated fashion:

# /usr/lib/yp/ypinit -m

If you use this way you may skip manually adding lines to /var/yp/ypservers.

/var/yp/securenets

Add rules to /var/yp/securenets to restrict access:

# 255.255.0.0 192.168.0.0 # Gives access to anyone in 192.168.0.0/16

Be sure to comment out this line, as it gives access to anyone.

# 0.0.0.0      0.0.0.0

/var/yp/ypservers

Add your server to /var/yp/ypservers:

# your.nis.server

Set your domain name

# ypdomainname EXAMPLE.COM

Now edit the /etc/yp.conf file and add your ypserver or nis server.

ypserver nis_server

Start NIS Daemons

Note: The daemons MUST be started in this order.

Start/enable the following systemd units:

  • rpcbind.service
  • ypbind.service
  • ypserv.service
  • yppasswdd.service (to allow clients to change their password with passwd)

NIS Client

Install Packages

The first step is to install the tools that you need. This provides the configuration files and general tools needed to use NIS.

# pacman -S yp-tools ypbind-mt
Warning: To users of server-side port security: Due to a problem in libtirpc 1.0.3, ypbind-mt won't be able to retrieve port-secured content anymore. Downgrading to libtirpc-1.0.2-3 fixes the issue for now. Watch https://github.com/thkukuk/ypbind-mt/issues/1 and https://bugs.archlinux.org/index.php?do=details&task_id=58502 until it got fixed.

Configuration

Set your domain name

# ypdomainname EXAMPLE.COM

You can apply this permanently by editing /etc/nisdomainname and adding:

# NISDOMAINNAME="EXAMPLE.COM"

Now edit the /etc/yp.conf file and add your ypserver or nis server.

ypserver nis_server

/etc/hosts

It may be a good idea to add your NIS server to /etc/hosts

192.168.1.10   nis_server.domain.com   nis_server

Start NIS Daemons

Note: The daemons MUST be started in this order.

Start/enable the rpcbind.service and ypbind.service systemd units.

Early testing

To test the setup so far you can run the command yptest:

# yptest

If it works you will, among other things, see the contents of the NIS user database (which is printed in the same format as /etc/passwd).

/etc/nsswitch.conf

To actually use NIS to log in you have to edit /etc/nsswitch.conf. Modify the lines for passwd, group and shadow to read:

passwd: files nis
group: files nis
shadow: files nis

And then do not forget

# systemctl restart ypbind

/etc/pam.d/passwd

To allow a user on a client machine to change their password on the server, be sure that yppasswdd.service is started/enabled on the server.

Edit /etc/pam.d/passwd on the client to add the nis parameter to password/pam_unix.so:

password     required     pam_unix.so sha512 shadow nullok nis

See section 7 of The Linux NIS HOWTO for further information on configuring NIS clients.

Attention on Systemd V235 since 10/2017

Due a problem with sandboxing on systemd-logind, any IP connections from and to the systemd-logind service are now denied. This will cause failures to log in, even though yptest works as expected, and can also cause accounts-daemon to crash outright. The basic problem is that the default /usr/lib/systemd/system/systemd-logind.service file that ships with systemd specifies IPAddressDeny=any, and this prevents it from communicating with the NIS server at login.

There are a few possible solutions:

  • Whitelist the address or address range of your NIS server:
This can be done by creating a new .conf file within the /etc/systemd/system/systemd-logind.service.d/, with these lines (the following allows connections from 10.0.*.*, edit as appropriate):
/etc/systemd/system/systemd-logind.service.d/open_network_interface.conf
echo -e [Service]
IPAddressAllow=10.0.0.0/16
This survives a reboot and updates of the systemd toolchain. It also avoid having to open your system to any IP address.
Note: there is no point in using IPAddressAllow=any, this is does not override the default IPAddressDeny=any set in the main unit file.
  • Override the system's default systemd-logind.service with a modified local version:
# cp -a /usr/lib/systemd/system/systemd-logind.service /etc/systemd/system
# nano /etc/systemd/system/systemd-logind.service 

and comment out the line IPAddressDeny=any to read # IPAddressDeny=any

This solution survives an update of the systemd toolchain and keeps working after a reboot. It does however override all settings in the unit file supplied with systemd, which may cause issues down the track if other unrelated settings are changed upstream. It also opens up access to any IP address, which is not recommended.

  • Modify the system's default systemd-logind.service directly:

Works, but not a recommended solution since it will not survive an update of the systemd toolchain:

# nano /usr/lib/systemd/system/systemd-logind.service 

and comment out the line IPAddressDeny=any to read # IPAddressDeny=any

Note that this also opens up access to any IP address, which is not recommended.

More resources