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 unnecessary, 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
.