nss-myhostname, libnss_myhostname.so.2 - Hostname resolution for the locally configured system hostname
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.
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.