<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> <refentry id="systemd-userdbd.service" conditional='ENABLE_USERDB'> <refentryinfo> <title>systemd-userdbd.service</title> <productname>systemd</productname> </refentryinfo> <refmeta> <refentrytitle>systemd-userdbd.service</refentrytitle> <manvolnum>8</manvolnum> </refmeta> <refnamediv> <refname>systemd-userdbd.service</refname> <refname>systemd-userdbd</refname> <refpurpose>JSON User/Group Record Query Multiplexer/NSS Compatibility</refpurpose> </refnamediv> <refsynopsisdiv> <para><filename>systemd-userdbd.service</filename></para> <para><filename>/usr/lib/systemd/systemd-userdbd</filename></para> </refsynopsisdiv> <refsect1> <title>Description</title> <para><command>systemd-userdbd</command> is a system service that multiplexes user/group lookups to all local services that provide JSON user/group record definitions to the system. In addition it synthesizes JSON user/group records from classic UNIX/glibc NSS user/group records in order to provide full backwards compatibility. It may also pick up statically defined JSON user/group records from drop-in files in <filename>/etc/userdb/</filename>, <filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename> and <filename>/use/lib/userdb/</filename>.</para> <para>Most of <command>systemd-userdbd</command>'s functionality is accessible through the <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> command.</para> <para>The user and group records this service provides access to follow the <ulink url="https://systemd.io/USER_RECORD">JSON User Record</ulink> and <ulink url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> definitions. This service implements the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via Varlink</ulink>, and multiplexes access other services implementing this API, too. It is thus both server and client of this API.</para> <para>This service provides three distinct <ulink url="https://varlink.org/">Varlink</ulink> services: <constant>io.systemd.Multiplexer</constant> provides a single, unified API for querying JSON user and group records. Internally it talks to all other user/group record services running on the system in parallel and forwards any information discovered. This simplifies clients substantially since they need to talk to a single service only instead of all of them in parallel. <constant>io.systemd.NameServiceSwitch</constant> provides compatibility with classic UNIX/glibc NSS user records, i.e. converts <type>struct passwd</type> and <type>struct group</type> records as acquired with APIs such as <citerefentry project='man-pages'><refentrytitle>getpwnam</refentrytitle><manvolnum>1</manvolnum></citerefentry> to JSON user/group records, thus hiding the differences between the services as much as possible. <constant>io.systemd.Dropin</constant> makes JSON user/group records from the aforementioned drop-in directories available.</para> </refsect1> <refsect1> <title>See Also</title> <para> <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> </para> </refsect1> </refentry>