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138 lines
6.4 KiB
XML
138 lines
6.4 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="nss-systemd" conditional='ENABLE_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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</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>UNIX user and group name resolution for user/group lookup via Varlink</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)
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functionality of the GNU C Library (<command>glibc</command>), providing UNIX user and group name
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resolution for services implementing the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record
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Lookup API via Varlink</ulink>, such as the system and service manager
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> (for its
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<varname>DynamicUser=</varname> feature, see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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details),
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<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</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>This module preferably utilizes
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<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for resolving users and groups, but also works without the service running.</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>Configuration in <filename>/etc/nsswitch.conf</filename></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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<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
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<programlisting>passwd: compat <command>systemd</command>
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group: compat [SUCCESS=merge] <command>systemd</command>
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shadow: compat
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hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns
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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>Example: Mappings provided by <filename>systemd-machined.service</filename></title>
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<para>The container <literal>rawhide</literal> is spawned using
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<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
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</para>
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<programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
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Spawning container rawhide on /var/lib/machines/rawhide.
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Selected user namespace base 20119552 and range 65536.
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...
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$ machinectl --max-addresses=3
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MACHINE CLASS SERVICE OS VERSION ADDRESSES
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rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
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$ getent passwd vu-rawhide-0 vu-rawhide-81
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vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin
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vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin
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$ getent group vg-rawhide-0 vg-rawhide-81
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vg-rawhide-0:*:20119552:
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vg-rawhide-81:*:20119633:
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$ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide'
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vu-rawhide-0 692 ? /usr/lib/systemd/systemd
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vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald
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vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd
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vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved
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vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind
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vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
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vu-rawhide-0 746 ? /usr/sbin/sshd -D ...
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vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user
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vu-rawhide-0 753 ? (sd-pam)
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vu-rawhide-0 1628 ? login -- zbyszek
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vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user
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vu-rawhide-1000 1631 ? (sd-pam)
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vu-rawhide-1000 1637 pts/8 -zsh
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</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><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-machined.service</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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