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systemd-stable/man/nss-myhostname.xml
Zbigniew Jędrzejewski-Szmek 56ba3c78ae build-sys: create Makefile-man.am automatically
man rules were repeating the same information in too many places,
which was error prone. Those rules can be easily generated from .xml
files. For efficiency and because python is not a required dependency,
Makefile-man.am is only regenerated when requested with

  make update-man-list

If no metadata in man/*.xml changed, this file should not change. So
only when a new man page or a new alias is added, this file should
show up in 'git diff'. The change should then be committed.

If the support for building from git without python was dropped, we
could drop Makefile-man.am from version control. This would also
increase the partial build time (since more stuff would be rebuild
whenever sources in man/*.xml would be modified), so it would probably
wouldn't be worth it.
2013-02-06 23:16:16 -05:00

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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 host name resolution for the locally
configured system hostname.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>nss-myhostname.la</command>
</cmdsynopsis>
</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 (wich 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>