nss-myhostname, libnss_myhostname.so.2 − Provide hostname resolution for the locally configured system hostname.
libnss_myhostname.so.2
nss−myhostname is a plugin 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:
• The local, configured hostname is resolved to all locally configured IP addresses ordered by their scope, or — if none are configured — the IPv4 address 127.0.0.2 (which is on the local loopback) and the IPv6 address ::1 (which is the local host).
• The hostname "localhost" is resolved to the IP addresses 127.0.0.1 and ::1.
• The hostname "gateway" is resolved to all current default routing gateway addresses, ordered by their metric. This assigns a stable hostname to the current gateway, useful for referencing it independently of the current network configuration state.
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 unncessary, and on many systems the file becomes entirely optional.
To activate the NSS modules, "myhostname" has to be added to the line starting with "hosts:" in /etc/nsswitch.conf.
It is recommended to place "myhostname" last in the nsswitch.conf line to make sure that this mapping is only used as fallback, and any DNS or /etc/hosts based mapping takes precedence.
Here's an example /etc/nsswitch.conf file, that enables myhostname correctly:
passwd: compat
group: compat
shadow: compat
hosts: files
dns mymachines myhostname
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.
systemd(1), nss-mymachines(8), nsswitch.conf(5), getent(1)