NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | COLOPHON

NSS-MYHOSTNAME(8)              nss-myhostname              NSS-MYHOSTNAME(8)

NAME         top

       nss-myhostname, libnss_myhostname.so.2 - Provide hostname resolution
       for the locally configured system hostname.

SYNOPSIS         top

       libnss_myhostname.so.2

DESCRIPTION         top

       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         top

       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 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         top

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

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
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systemd 231                                                NSS-MYHOSTNAME(8)