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<?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 hostname 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 hostname 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 hostname. 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 configured 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 hostname 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>
|
