mirror of
https://github.com/systemd/systemd.git
synced 2024-12-26 03:22:00 +03:00
08540a9591
This adds -Dnss-resolve= and -Dnss-mymachines= meson options. By using this option, e.g., resolved can be built without nss-resolve. When no nss modules are built, then test-nss is neither built. Also, This changes the option name -Dmyhostname= to -Dnss-myhostname= for consistency to other nss related options. Closes #9596.
125 lines
4.9 KiB
XML
125 lines
4.9 KiB
XML
<?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">
|
|
|
|
<!--
|
|
SPDX-License-Identifier: LGPL-2.1+
|
|
-->
|
|
|
|
<refentry id="nss-myhostname" conditional='ENABLE_NSS_MYHOSTNAME'>
|
|
|
|
<refentryinfo>
|
|
<title>nss-myhostname</title>
|
|
<productname>systemd</productname>
|
|
</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 mymachines resolve [!UNAVAIL=return] dns <command>myhostname</command>
|
|
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>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>
|