nss-myhostname - Man Page

Hostname resolution for the locally configured system hostname

Synopsis

libnss_myhostname.so.2

Description

nss-myhostname is a plug-in module for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc), primarily providing hostname resolution for the locally configured system hostname as returned by gethostname(2). The precise hostnames resolved by this module are:

Various software relies on an always-resolvable local hostname. When using dynamic hostnames, this is traditionally achieved by patching /etc/hosts at the same time as changing the hostname. This is problematic since it requires a writable /etc/ file system and is fragile because the file might be edited by the administrator at the same time. With nss-myhostname enabled, changing /etc/hosts is unnecessary, and on many systems, the file becomes entirely optional.

To activate the NSS modules, add "myhostname" to the line starting with "hosts:" in /etc/nsswitch.conf.

It is recommended to place "myhostname" after "file" and before "dns". This resolves well-known hostnames like "localhost" and the machine hostnames locally. It is consistent with the behaviour of nss-resolve, and still allows overriding via /etc/hosts.

Please keep in mind that nss-myhostname (and nss-resolve) also resolve in the other direction — from locally attached IP adresses to hostnames. If you rely on that lookup being provided by DNS, you might want to order things differently.

Example

Here is an example /etc/nsswitch.conf file that enables nss-myhostname correctly:

passwd:         compat systemd
group:          compat [SUCCESS=merge] systemd
shadow:         compat systemd
gshadow:        files systemd


hosts:          mymachines resolve [!UNAVAIL=return] files myhostname dns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

To test, use glibc's getent tool:

$ getent ahosts `hostname`
::1       STREAM omega
::1       DGRAM
::1       RAW
127.0.0.2       STREAM
127.0.0.2       DGRAM
127.0.0.2       RAW

In this case, the local hostname is omega.

See Also

systemd(1), nss-systemd(8), nss-resolve(8), nss-mymachines(8), nsswitch.conf(5), getent(1)

Referenced By

nss-mymachines(8), nss-resolve(8), nss-systemd(8), systemd.directives(7), systemd.index(7).

The man page libnss_myhostname.so.2(8) is an alias of nss-myhostname(8).

systemd 249