bionic (8) nss-myhostname.8.gz

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)