man/systemd-userdbd.service.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="systemd-userdbd.service" conditional='ENABLE_USERDB'>
   7
   8   <refentryinfo>
   9     <title>systemd-userdbd.service</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-userdbd.service</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-userdbd.service</refname>
  20     <refname>systemd-userdbd</refname>
  21     <refpurpose>JSON User/Group Record Query Multiplexer/NSS Compatibility</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>systemd-userdbd.service</filename></para>
  26     <para><filename>/usr/lib/systemd/systemd-userdbd</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><command>systemd-userdbd</command> is a system service that multiplexes user/group lookups to all
  33     local services that provide JSON user/group record definitions to the system. In addition it synthesizes
  34     JSON user/group records from classic UNIX/glibc NSS user/group records in order to provide full backwards
  35     compatibility. It may also pick up statically defined JSON user/group records from files in
  36     <filename>/etc/userdb/</filename>, <filename>/run/userdb/</filename>,
  37     <filename>/run/host/userdb/</filename> and <filename>/usr/lib/userdb/</filename> with the
  38     <literal>.user</literal> extension.</para>
  39
  40     <para>Most of <command>systemd-userdbd</command>'s functionality is accessible through the
  41     <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  42     command.</para>
  43
  44     <para>The user and group records this service provides access to follow the <ulink
  45     url="https://systemd.io/USER_RECORD">JSON User Records</ulink> and <ulink
  46     url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> definitions. This service implements the
  47     <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via Varlink</ulink>, and
  48     multiplexes access other services implementing this API, too. It is thus both server and client of this
  49     API.</para>
  50
  51     <para>This service provides three distinct <ulink url="https://varlink.org/">Varlink</ulink> services:
  52     <constant>io.systemd.Multiplexer</constant> provides a single, unified API for querying JSON user and
  53     group records. Internally it talks to all other user/group record services running on the system in
  54     parallel and forwards any information discovered. This simplifies clients substantially since they need
  55     to talk to a single service only instead of all of them in
  56     parallel. <constant>io.systemd.NameServiceSwitch</constant> provides compatibility with classic
  57     UNIX/glibc NSS user records, i.e. converts <type>struct passwd</type> and <type>struct group</type>
  58     records as acquired with APIs such as <citerefentry
  59     project='man-pages'><refentrytitle>getpwnam</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
  60     JSON user/group records, thus hiding the differences between the services as much as
  61     possible. <constant>io.systemd.DropIn</constant> makes JSON user/group records from the aforementioned
  62     drop-in directories available.</para>
  63   </refsect1>
  64
  65   <refsect1>
  66     <title>See Also</title>
  67     <para><simplelist type="inline">
  68       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
  69       <member><citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
  70       <member><citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
  71       <member><citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
  72     </simplelist></para>
  73   </refsect1>
  74 </refentry>