NIS - ArchWiki

# 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. Install yp-toolsAUR ypbind-mtAUR.

Warning: To users of server-side port security: Due to a problem in libtirpc 1.0.3, ypbind-mt will not 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 (and V239 since 06/2018, and V245 since 03/2020)

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. Moreover, since V239, that file also specifies `RestrictAddressFamilies=AF_UNIX AF_NETLINK`, dropping `AF_INET AF_INET6` from the list.

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

    [Service]
    RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
    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`. As of V239, you will also need to add `AF_INET AF_INET6` to the `RestrictAddressFamilies=AF_UNIX AF_NETLINK` line.

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`. As of V239, you will also need to add `AF_INET AF_INET6` to the `RestrictAddressFamilies=AF_UNIX AF_NETLINK` line.

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

##### systemd-userdbd.service

After updating nis clients to systemd 245-1, the systemd-userdbd.service can be affected by a similar issue as the systemd-logind.service which can cause 25 second login delays.

Create a new `.conf` file within `/etc/systemd/system/systemd-userdbd.service.d/` containing your NIS server IP address to correct the issue...

    [Service]
    IPAddressAllow=n.n.n.n/32

## More resources

- The Linux NIS HOWTO,very helpful and generally applicable to Arch Linux.
- YoLinux NIS tutorial
- Quick HOWTO, Configuring NIS

Category:

- Directory services