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systemd/man/userdbctl.xml
Lennart Poettering 01f6c450b6 man: document new --chain switch to userdbctl
And while we are at it, make 'ssh-authorized-keys' verb properly
documented. Given that OpenSSH documents the interface in its man page
it's fine to just document our implementation of it too.
2021-11-11 10:06:39 +01:00

347 lines
17 KiB
XML

<?xml version='1.0'?>
<!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="userdbctl" conditional='ENABLE_USERDB'
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>userdbctl</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>userdbctl</refentrytitle>
<manvolnum>1</manvolnum>
</refmeta>
<refnamediv>
<refname>userdbctl</refname>
<refpurpose>Inspect users, groups and group memberships</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>userdbctl</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="req">COMMAND</arg>
<arg choice="opt" rep="repeat">NAME</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>userdbctl</command> may be used to inspect user and groups (as well as group memberships)
of the system. This client utility inquires user/group information provided by various system services,
both operating on JSON user/group records (as defined by the <ulink
url="https://systemd.io/USER_RECORD">JSON User Records</ulink> and <ulink
url="https://systemd.io/GROUP_RECORD">JSON Group Records</ulink> definitions), and classic UNIX NSS/glibc
user and group records. This tool is primarily a client to the <ulink
url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via Varlink</ulink>, and may also
pick up drop-in JSON user and group records from <filename>/etc/userdb/</filename>,
<filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename>,
<filename>/usr/lib/userdb/</filename>.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--output=</option><replaceable>MODE</replaceable></term>
<listitem><para>Choose the output mode, takes one of <literal>classic</literal>,
<literal>friendly</literal>, <literal>table</literal>, <literal>json</literal>. If
<literal>classic</literal>, an output very close to the format of <filename>/etc/passwd</filename> or
<filename>/etc/group</filename> is generated. If <literal>friendly</literal> a more comprehensive and
user friendly, human readable output is generated; if <literal>table</literal> a minimal, tabular
output is generated; if <literal>json</literal> a JSON formatted output is generated. Defaults to
<literal>friendly</literal> if a user/group is specified on the command line,
<literal>table</literal> otherwise.</para>
<para>Note that most output formats do not show all available information. In particular,
<literal>classic</literal> and <literal>table</literal> show only the most important fields. Various
modes also do not show password hashes. Use <literal>json</literal> to view all fields, including
any authentication fields.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--json=</option><replaceable>FORMAT</replaceable></term>
<listitem><para>Selects JSON out mode (like <option>--output=json</option>) and selects the precise
display mode. Takes one of <literal>pretty</literal> or <literal>short</literal>. If
<literal>pretty</literal> human-friendly whitespace and newlines are inserted in the output to make
the JSON data more readable. If <literal>short</literal> all superfluous whitespace is
suppressed.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--service=</option><replaceable>SERVICE</replaceable><optional>:<replaceable>SERVICE…</replaceable></optional></term>
<term><option>-s</option> <replaceable>SERVICE</replaceable>:<replaceable>SERVICE…</replaceable></term>
<listitem><para>Controls which services to query for users/groups. Takes a list of one or more
service names, separated by <literal>:</literal>. See below for a list of well-known service
names. If not specified all available services are queried at once.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--with-nss=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Controls whether to include classic glibc/NSS user/group lookups in the output. If
<option>--with-nss=no</option> is used any attempts to resolve or enumerate users/groups provided
only via glibc NSS is suppressed. If <option>--with-nss=yes</option> is specified such users/groups
are included in the output (which is the default).</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--with-varlink=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Controls whether to include Varlink user/group lookups in the output, i.e. those done
via the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via
Varlink</ulink>. If <option>--with-varlink=no</option> is used any attempts to resolve or enumerate
users/groups provided only via Varlink are suppressed. If <option>--with-varlink=yes</option> is
specified such users/groups are included in the output (which is the default).</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--with-dropin=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Controls whether to include user/group lookups in the output that are defined using
drop-in files in <filename>/etc/userdb/</filename>, <filename>/run/userdb/</filename>,
<filename>/run/host/userdb/</filename>, <filename>/usr/lib/userdb/</filename>. If
<option>--with-dropin=no</option> is used these records are suppressed. If
<option>--with-dropin=yes</option> is specified such users/groups are included in the output (which
is the default).</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--synthesize=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Controls whether to synthesize records for the root and nobody users/groups if they
aren't defined otherwise. By default (or <literal>yes</literal>) such records are implicitly
synthesized if otherwise missing since they have special significance to the OS. When
<literal>no</literal> this synthesizing is turned off.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-N</option></term>
<listitem><para>This option is short for <option>--with-nss=no</option>
<option>--synthesize=no</option>. Use this option to show only records that are natively defined as
JSON user or group records, with all NSS/glibc compatibility and all implicit synthesis turned
off.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--multiplexer=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Controls whether to do lookups via the multiplexer service (if specified as true, the
default) or do lookups in the client (if specified as false). Using the multiplexer service is
typically preferable, since it runs in a locked down sandbox.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--chain</option></term>
<listitem><para>When used with the <command>ssh-authorized-keys</command> command, this will allow
passing an additional command line after the user name that is chain executed after the lookup
completed. This allows chaining multiple tools that show SSH authorized keys.</para></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="no-pager" />
<xi:include href="standard-options.xml" xpointer="no-legend" />
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Commands</title>
<para>The following commands are understood:</para>
<variablelist>
<varlistentry>
<term><command>user</command> <optional><replaceable>USER</replaceable></optional></term>
<listitem><para>List all known users records or show details of one or more specified user
records. Use <option>--output=</option> to tweak output mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>group</command> <optional><replaceable>GROUP</replaceable></optional></term>
<listitem><para>List all known group records or show details of one or more specified group
records. Use <option>--output=</option> to tweak output mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>users-in-group</command> <optional><replaceable>GROUP</replaceable></optional></term>
<listitem><para>List users that are members of the specified groups. If no groups are specified list
all user/group memberships defined. Use <option>--output=</option> to tweak output
mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>groups-of-user</command> <optional><replaceable>USER</replaceable></optional></term>
<listitem><para>List groups that the specified users are members of. If no users are specified list
all user/group memberships defined (in this case <command>groups-of-user</command> and
<command>users-in-group</command> are equivalent). Use <option>--output=</option> to tweak output
mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>services</command></term>
<listitem><para>List all services currently providing user/group definitions to the system. See below
for a list of well-known services providing user information.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>ssh-authorized-keys</command></term>
<listitem><para>Show SSH authorized keys for this account. This command is intended to be used to
allow the SSH daemon to pick up authorized keys from user records, see below.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Well-Known Services</title>
<para>The <command>userdbctl services</command> command will list all currently running services that
provide user or group definitions to the system. The following well-known services are shown among
this list:</para>
<variablelist>
<varlistentry>
<term><constant>io.systemd.DynamicUser</constant></term>
<listitem><para>This service is provided by the system service manager itself (i.e. PID 1) and
makes all users (and their groups) synthesized through the <varname>DynamicUser=</varname> setting in
service unit files available to the system (see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
details about this setting).</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>io.systemd.Home</constant></term>
<listitem><para>This service is provided by
<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and makes all users (and their groups) belonging to home directories managed by that service
available to the system.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>io.systemd.Machine</constant></term>
<listitem><para>This service is provided by
<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and synthesizes records for all users/groups used by a container that employs user
namespacing.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>io.systemd.Multiplexer</constant></term>
<listitem><para>This service is provided by
<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and multiplexes user/group look-ups to all other running lookup services. This is the primary entry point
for user/group record clients, as it simplifies client side implementation substantially since they
can ask a single service for lookups instead of asking all running services in parallel.
<command>userdbctl</command> uses this service preferably, too, unless <option>--with-nss=</option>
or <option>--service=</option> are used, in which case finer control over the services to talk to is
required.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>io.systemd.NameServiceSwitch</constant></term>
<listitem><para>This service is (also) provided by
<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and converts classic NSS/glibc user and group records to JSON user/group records, providing full
backwards compatibility. Use <option>--with-nss=no</option> to disable this compatibility, see
above. Note that compatibility is actually provided in both directions:
<citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry> will
automatically synthesize classic NSS/glibc user/group records from all JSON user/group records
provided to the system, thus using both APIs is mostly equivalent and provides access to the same
data, however the NSS/glibc APIs necessarily expose a more reduced set of fields
only.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>io.systemd.DropIn</constant></term>
<listitem><para>This service is (also) provided by
<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and picks up JSON user/group records from <filename>/etc/userdb/</filename>,
<filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename>,
<filename>/usr/lib/userdb/</filename>.</para></listitem>
</varlistentry>
</variablelist>
<para>Note that <command>userdbctl</command> has internal support for NSS-based lookups too. This means
that if neither <constant>io.systemd.Multiplexer</constant> nor
<constant>io.systemd.NameServiceSwitch</constant> are running look-ups into the basic user/group
databases will still work.</para>
</refsect1>
<refsect1>
<title>Integration with SSH</title>
<para>The <command>userdbctl</command> tool may be used to make the list of SSH authorized keys possibly
contained in a user record available to the SSH daemon for authentication. For that configure the
following in <citerefentry
project='die-net'><refentrytitle>sshd_config</refentrytitle><manvolnum>5</manvolnum></citerefentry>:</para>
<programlisting>
AuthorizedKeysCommand /usr/bin/userdbctl ssh-authorized-keys %u
AuthorizedKeysCommandUser root
</programlisting>
<para>Sometimes it's useful to allow chain invocation of another program to list SSH authorized keys. By
using the <option>--chain</option> such a tool may be chain executed by <command>userdbctl
ssh-authorized-keys</command> once a lookup completes (regardless if an SSH key was found or
not). Example:</para>
<programlisting>
AuthorizedKeysCommand /usr/bin/userdbctl ssh-authorized-keys %u --chain /usr/bin/othertool %u
AuthorizedKeysCommandUser root
</programlisting>
<para>The above will first query the userdb database for SSH keys, and then chain execute
<command>/usr/bin/othertool</command> to also be queried.</para>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>On success, 0 is returned, a non-zero failure code otherwise.</para>
</refsect1>
<xi:include href="common-variables.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>