# NIS

From ArchWiki
Jump to navigation Jump to search
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.

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