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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.

## 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

    #<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 is a bug, maybe it is a feature), which will always add the first line in `/etc/hosts` to the list of ypservers.

#### /etc/nisdomainname

Add the domain name:

    /etc/nisdomainname

    # NISDOMAINNAME="nis-domain-name"

#### /etc/ypserv.conf

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

    /etc/ypserv.conf

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

For example:

    /etc/ypserv.conf

    # 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:

    /var/yp/securenets

    # 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.

    /var/yp/securenets

    # 0.0.0.0      0.0.0.0

#### /var/yp/ypservers

Add your server to `/var/yp/ypservers`:

    /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.

    /etc/yp.conf

    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.

### 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 to restart `ypbind.service`.

#### /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.

#### Connections after Systemd V235

Due to 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 `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.

The solution is to whitelist the address or address range of your NIS server.

Another systemd sandboxing element related to namespace management ("ProtectHostname") may prevent proper operation. The following snippet turns that off too.

Use a drop-in unit file for `systemd-logind.service`, 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
    ProtectHostname=no

##### 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.

Use a drop-in unit file for `systemd-userdbd.service` containing your NIS server IP address to correct the issue.

    /etc/systemd/system/systemd-userdbd.service.d/override.conf

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

(Alternately, the same drop-in file used for systemd-logind.service could be used.)

## More resources

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

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