<?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">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
This file is part of systemd.
Copyright 2011 Lennart Poettering
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
+<refentry id="nss-myhostname" conditional='ENABLE_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>
+ <refname>libnss_myhostname.so.2</refname>
+ <refpurpose>Provide hostname resolution for the locally
+ configured system hostname.</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>libnss_myhostname.so.2</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><command>nss-myhostname</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
+ the GNU C Library (<command>glibc</command>), primarily providing hostname resolution for the locally configured
+ system hostname as returned by
+ <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>. The precise
+ hostnames resolved by this module are:</para>
+
+ <itemizedlist>
+ <listitem><para>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).</para></listitem>
+
+ <listitem><para>The hostnames <literal>localhost</literal> and
+ <literal>localhost.localdomain</literal> (as well as any hostname
+ ending in <literal>.localhost</literal> or <literal>.localhost.localdomain</literal>)
+ are resolved to the IP addresses 127.0.0.1 and ::1.</para></listitem>
+
+ <listitem><para>The hostname <literal>_gateway</literal> 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.</para></listitem>
+ </itemizedlist>
+
+ <para>Various software relies on an always-resolvable local
+ hostname. When using dynamic hostnames, this is traditionally
+ achieved by patching <filename>/etc/hosts</filename> at the same
+ time as changing the hostname. This is problematic 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. With <command>nss-myhostname</command> enabled,
+ changing <filename>/etc/hosts</filename> is unnecessary, and on
+ many systems, the file becomes entirely optional.</para>
+
+ <para>To activate the NSS modules, add <literal>myhostname</literal> to the line starting with
+ <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
+
+ <para>It is recommended to place <literal>myhostname</literal> last in the <filename>nsswitch.conf</filename>'
+ <literal>hosts:</literal> line to make sure that this mapping is only used as fallback, and that any DNS or
+ <filename>/etc/hosts</filename> based mapping takes precedence.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Example</title>
+
+ <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
+ <command>nss-myhostname</command> correctly:</para>
+
+<programlisting>passwd: compat mymachines systemd
+group: compat mymachines systemd
shadow: compat
-hosts: files dns <varname>myhostname</varname>
+hosts: files mymachines resolve [!UNAVAIL=return] dns <command>myhostname</command>
networks: files
protocols: db files
ethers: db files
rpc: db files
-netgroup: nis
- </programlisting>
+netgroup: nis</programlisting>
-
<para>To test, use <command>glibc</command>'s <command>getent</command> tool:</para>
+ <para>To test, use <command>glibc</command>'s <command>getent</command> tool:</para>
- <programlisting>
-$ getent ahosts `hostname`
-::1 STREAM omega
-::1 DGRAM
-::1 RAW
+ <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>
+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>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff