<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2011 Lennart Poettering Copyright 2013 Tom Gundersen systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <refentry id="nss-myhostname" conditional='HAVE_MYHOSTNAME'> <refentryinfo> <title>nss-myhostname</title> <productname>systemd</productname> <authorgroup> <author> <contrib>Developer</contrib> <firstname>Lennart</firstname> <surname>Poettering</surname> <email>lennart@poettering.net</email> </author> </authorgroup> </refentryinfo> <refmeta> <refentrytitle>nss-myhostname</refentrytitle> <manvolnum>8</manvolnum> </refmeta> <refnamediv> <refname>nss-myhostname</refname> <refpurpose>Provide host name resolution for the locally configured system hostname.</refpurpose> </refnamediv> <refsynopsisdiv> <para><filename>nss-myhostname.la</filename></para> </refsynopsisdiv> <refsect1> <title>Description</title> <para><command>nss-myhostname</command> is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (<command>glibc</command>) providing host name resolution for the locally configured system hostname as returned by <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>. Various software relies on an always resolvable local host name. When using dynamic hostnames this is usually achieved by patching <filename>/etc/hosts</filename> at the same time as changing the host name. This however is not ideal since it requires a writable <filename>/etc</filename> file system and is fragile because the file might be edited by the administrator at the same time. <command>nss-myhostname</command> simply returns all locally configure public IP addresses, 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) for whatever system hostname is configured locally. Patching <filename>/etc/hosts</filename> is thus no longer necessary.</para> <para>To activate the NSS modules, <option>myhostname</option> has to be added to the line starting with "<varname>hosts:</varname>" in <filename>/etc/nsswitch.conf</filename></para> <para>It is recommended to put <option>myhostname</option> last in the <filename>nsswitch.conf</filename> line to make sure that this mapping is only used as fallback, and any DNS or <filename>/etc/hosts</filename> based mapping takes precedence.</para> </refsect1> <refsect1> <title>Example</title> <programlisting> # /etc/nsswitch.conf passwd: compat group: compat shadow: compat hosts: files dns <varname>myhostname</varname> networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis </programlisting> <para>To test, use <command>glibc</command>'s <command>getent</command> tool:</para> <programlisting> $ 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 </programlisting> <para>In this case the local host name is <varname>omega</varname>.</para> </refsect1> <refsect1> <title>See Also</title> <para> <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry> </para> </refsect1> </refentry>