huschi.net

NSS-MYHOSTNAME(8)               nss-myhostname               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:
       o   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).
       o   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.
       o   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)
systemd 239                                                  NSS-MYHOSTNAME(8)