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2129011e92
Let's extend nss-systemd to also synthesize user/group entries for the UIDs/GIDs 0 and 65534 which have special kernel meaning. Given that nss-systemd is listed in /etc/nsswitch.conf only very late any explicit listing in /etc/passwd or /etc/group takes precedence. This functionality is useful in minimal container-like setups that lack /etc/passwd files (or only have incompletely populated ones).
112 lines
4.3 KiB
XML
112 lines
4.3 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2016 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="nss-systemd">
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<refentryinfo>
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<title>nss-systemd</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>nss-systemd</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>nss-systemd</refname>
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<refname>libnss_systemd.so.2</refname>
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<refpurpose>Provide UNIX user and group name resolution for dynamic users and groups.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>libnss_systemd.so.2</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
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GNU C Library (<command>glibc</command>), providing UNIX user and group name resolution for dynamic users and
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groups allocated through the <varname>DynamicUser=</varname> option in systemd unit files. See
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details on
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this option.</para>
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<para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs
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0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or
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<filename>/etc/group</filename>, or if these files are missing.</para>
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<para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with
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<literal>passwd:</literal> and <literal>group:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
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<para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> or
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<literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines so that
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<filename>/etc/passwd</filename> and <filename>/etc/group</filename> based mappings take precedence.</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
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<command>nss-systemd</command> correctly:</para>
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<programlisting>passwd: compat mymachines <command>systemd</command>
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group: compat mymachines <command>systemd</command>
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shadow: compat
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hosts: files mymachines resolve myhostname
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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