systemd/man/userdbctl.xml

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<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 output 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>