1<?xml version='1.0'?> <!--*-nxml-*-->
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/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 drop-in files in
36    <filename>/etc/userdb/</filename>, <filename>/run/userdb/</filename>,
37    <filename>/run/host/userdb/</filename> and <filename>/usr/lib/userdb/</filename>.</para>
38
39    <para>Most of <command>systemd-userdbd</command>'s functionality is accessible through the
40    <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
41    command.</para>
42
43    <para>The user and group records this service provides access to follow the <ulink
44    url="https://systemd.io/USER_RECORD">JSON User Records</ulink> and <ulink
45    url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> definitions. This service implements the
46    <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via Varlink</ulink>, and
47    multiplexes access other services implementing this API, too. It is thus both server and client of this
48    API.</para>
49
50    <para>This service provides three distinct <ulink url="https://varlink.org/">Varlink</ulink> services:
51    <constant>io.systemd.Multiplexer</constant> provides a single, unified API for querying JSON user and
52    group records. Internally it talks to all other user/group record services running on the system in
53    parallel and forwards any information discovered. This simplifies clients substantially since they need
54    to talk to a single service only instead of all of them in
55    parallel. <constant>io.systemd.NameServiceSwitch</constant> provides compatibility with classic
56    UNIX/glibc NSS user records, i.e. converts <type>struct passwd</type> and <type>struct group</type>
57    records as acquired with APIs such as <citerefentry
58    project='man-pages'><refentrytitle>getpwnam</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
59    JSON user/group records, thus hiding the differences between the services as much as
60    possible. <constant>io.systemd.Dropin</constant> makes JSON user/group records from the aforementioned
61    drop-in directories available.</para>
62  </refsect1>
63
64  <refsect1>
65    <title>See Also</title>
66    <para>
67      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
68      <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
69      <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
70      <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
71    </para>
72  </refsect1>
73</refentry>
74