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systemd/man/nss-systemd.xml
Lennart Poettering 75555c2824 man: sync up the suggested nsswitch.conf configuration for our four NSS modules
This unifies the suggested nsswitch.conf configuration for our four NSS modules to this:

    hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname

Note that this restores "myhostname" to the suggested configuration of
nss-resolve for the time being, undoing 4484e1792b.

"myhostname" should probably be dropped eventually, but when we do this we
should do it in full, and not only drop it from the suggested nsswitch.conf
for one of the modules, but also drop it in source and stop referring to it
altogether.

Note that nss-resolve doesn't replace nss-myhostname in full: the former only
works if D-Bus/resolved is available for resolving the local hostname, the
latter works in all cases even if D-Bus or resolved are not in operation, hence
there's some value in keeping the line as it is right now. Note that neither
dns nor myhostname are considered at all with the above configuration unless
the resolve module actually returns UNAVAIL. Thus, even though handling of
local hostname resolving is implemented twice this way it is only executed once
for each lookup.
2016-10-24 19:04:43 +02:00

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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 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
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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-systemd">
<refentryinfo>
<title>nss-systemd</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-systemd</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>nss-systemd</refname>
<refname>libnss_systemd.so.2</refname>
<refpurpose>Provide UNIX user and group name resolution for dynamic users and groups.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>libnss_systemd.so.2</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
GNU C Library (<command>glibc</command>), providing UNIX user and group name resolution for dynamic users and
groups allocated through the <varname>DynamicUser=</varname> option in systemd unit files. See
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details on
this option.</para>
<para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs
0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or
<filename>/etc/group</filename>, or if these files are missing.</para>
<para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with
<literal>passwd:</literal> and <literal>group:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
<para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> or
<literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines so that
<filename>/etc/passwd</filename> and <filename>/etc/group</filename> based mappings take precedence.</para>
</refsect1>
<refsect1>
<title>Example</title>
<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
<command>nss-systemd</command> correctly:</para>
<programlisting>passwd: compat mymachines <command>systemd</command>
group: compat mymachines <command>systemd</command>
shadow: compat
hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis</programlisting>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>nss-myhostname</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>