nss-myhostname
systemd
Developer
Lennart
Poettering
lennart@poettering.net
nss-myhostname
8
nss-myhostname
libnss_myhostname.so.2
Provide hostname resolution for the locally
configured system hostname.
libnss_myhostname.so.2
Description
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
gethostname2.
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 that any DNS or
/etc/hosts based mapping takes
precedence.
Example
Here's an example /etc/nsswitch.conf
file that enables myhostname correctly:
passwd: compat mymachines
group: compat mymachines
shadow: compat
hosts: files resolve 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.
See Also
systemd1,
nss-resolve8,
nss-mymachines8,
nsswitch.conf5,
getent1