nss-myhostname(8)

NAME

   nss-myhostname, libnss_myhostname.so.2 - Provide 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:

   *   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 hostnames "localhost" and "localhost.localdomain" (as well as
       any hostname ending in ".localhost" or ".localhost.localdomain")
       are 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, add "myhostname" to the line starting with
   "hosts:" in /etc/nsswitch.conf.

   It is recommended to place "myhostname" last in the nsswitch.conf'
   "hosts:" 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 is an example /etc/nsswitch.conf file that enables nss-myhostname
   correctly:

       passwd:         compat mymachines systemd
       group:          compat mymachines systemd
       shadow:         compat

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

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

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