systemd/man/varlinkctl.xml

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<refentry id="varlinkctl"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>varlinkctl</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>varlinkctl</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>varlinkctl</refname>
    <refpurpose>Introspect with and invoke Varlink services</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">info</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">list-interfaces</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">list-methods</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
      <arg choice="opt" rep="repeat"><replaceable>INTERFACE</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">introspect</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
      <arg choice="opt" rep="repeat"><replaceable>INTERFACE</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">call</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
      <arg choice="plain"><replaceable>METHOD</replaceable></arg>
      <arg choice="opt"><replaceable>ARGUMENTS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">validate-idl</arg>
      <arg choice="opt"><replaceable>FILE</replaceable></arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>varlinkctl</command> may be used to introspect and invoke <ulink
    url="https://varlink.org/">Varlink</ulink> services.</para>

    <para>Services are referenced by one of the following:</para>

    <itemizedlist>
      <listitem><para>A Varlink service reference starting with the <literal>unix:</literal> string, followed
      by an absolute <constant>AF_UNIX</constant> socket path, or by <literal>@</literal> and an arbitrary
      string (the latter for referencing sockets in the abstract namespace). In this case a stream socket
      connection is made to the specified socket.</para></listitem>

      <listitem><para>A Varlink service reference starting with the <literal>exec:</literal> string, followed
      by an absolute path of a binary to execute. In this case the specified process is forked off locally,
      with a connected stream socket passed in.</para></listitem>

      <listitem><para>A Varlink service reference starting with the <literal>ssh-unix:</literal> string, followed
      by an SSH host specification, followed by <literal>:</literal>, followed by an absolute
      <constant>AF_UNIX</constant> socket path. (This requires OpenSSH 9.4 or newer on the server side,
      abstract namespace sockets are not supported.)</para></listitem>

      <listitem><para>A Varlink service reference starting with the <literal>ssh-exec:</literal> string,
      followed by an SSH host specification, followed by <literal>:</literal>, followed by a command line. In
      this case the command is invoked and the Varlink protocol is spoken on the standard input and output of
      the invoked command.</para></listitem>
    </itemizedlist>

    <para>For convenience these two simpler (redundant) service address syntaxes are also supported:</para>

    <itemizedlist>
      <listitem><para>A file system path to an <constant>AF_UNIX</constant> socket, either absolute
      (i.e. begins with <literal>/</literal>) or relative (in which case it must begin with
      <literal>./</literal>).</para></listitem>

      <listitem><para>A file system path to an executable, either absolute or relative (as above, must begin
      with <literal>/</literal>, resp. <literal>./</literal>).</para></listitem>
    </itemizedlist>
  </refsect1>

  <refsect1>
    <title>Commands</title>

    <para>The following commands are understood:</para>

    <variablelist>
      <varlistentry>
        <term><command>info</command> <replaceable>ADDRESS</replaceable></term>

        <listitem><para>Show brief information about the specified service, including vendor name and list of
        implemented interfaces. Expects a service address in one of the formats described above.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>list-interfaces</command> <replaceable>ADDRESS</replaceable></term>

        <listitem><para>Show list of interfaces implemented by the specified service. Expects a service
        address in one of the formats described above.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>list-methods</command> <replaceable>ADDRESS</replaceable> [<replaceable>INTERFACE…</replaceable>]</term>

        <listitem><para>Show list of methods implemented by the specified service. Expects a service address
        in one of the formats described above as well as one or more interface names. If no interface name is
        specified, lists all methods of all interfaces implemented by the service, otherwise just the methods
        in the specified interfaces.</para>

        <xi:include href="version-info.xml" xpointer="v257"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>introspect</command> <replaceable>ADDRESS</replaceable> [<replaceable>INTERFACE…</replaceable>]</term>

        <listitem><para>Show the interface definitions of the specified interfaces provided by the specified
        service. Expects a service address in one of the formats described above and optionally one or more
        Varlink interface names. If no interface names are specified, shows all provided interfaces by the
        service.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>call</command> <replaceable>ADDRESS</replaceable> <replaceable>METHOD</replaceable> [<replaceable>ARGUMENTS</replaceable>]</term>

        <listitem><para>Call the specified method of the specified service. Expects a service address in the
        format described above, a fully qualified Varlink method name, and a JSON arguments object. If the
        arguments object is not specified, it is read from STDIN instead. To pass an empty list of
        parameters, specify the empty object <literal>{}</literal>.</para>

        <para>The reply parameters are written as JSON object to STDOUT.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>validate-idl</command> [<replaceable>FILE</replaceable>]</term>

        <listitem><para>Reads a Varlink interface definition file, parses and validates it, then outputs it
        with syntax highlighting. This checks for syntax and internal consistency of the interface. Expects a
        file name to read the interface definition from. If omitted reads the interface definition from
        STDIN.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>help</command></term>

        <listitem><para>Show command syntax help.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>--more</option></term>

        <listitem><para>When used with <command>call</command>: expect multiple method replies. If this flag is
        set the method call is sent with the <constant>more</constant> flag set, which tells the service to
        generate multiple replies, if needed. The command remains running until the service sends a reply
        message that indicates it is the last in the series. This flag should be set only for method calls
        that support this mechanism.</para>

        <para>If this mode is enabled output is automatically switched to JSON-SEQ mode, so that individual
        reply objects can be easily discerned.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--collect</option></term>

        <listitem><para>This is similar to <option>--more</option> but collects all responses in a JSON
        array, and prints it, rather than in JSON_SEQ mode.</para>

        <xi:include href="version-info.xml" xpointer="v256"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--oneway</option></term>

        <listitem><para>When used with <command>call</command>: do not expect a method reply. If this flag
        is set the method call is sent with the <constant>oneway</constant> flag set (the command exits
        immediately after), which tells the service not to generate a reply.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--json=<replaceable>MODE</replaceable></option></term>

        <listitem>
          <para>Selects the JSON output formatting, one of <literal>pretty</literal> (for nicely indented,
          colorized output) or <literal>short</literal> (for terse output with minimal whitespace and no
          newlines), defaults to <literal>short</literal>.</para>

        <xi:include href="version-info.xml" xpointer="v255"/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-j</option></term>

        <listitem>
          <para>Equivalent to <option>--json=pretty</option> when invoked interactively from a terminal. Otherwise
          equivalent to <option>--json=short</option>, in particular when the output is piped to some other
          program.</para>

        <xi:include href="version-info.xml" xpointer="v255"/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--quiet</option></term>
        <term><option>-q</option></term>

        <listitem>
          <para>Suppress output of method call replies.</para>

        <xi:include href="version-info.xml" xpointer="v257"/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--graceful=</option></term>

        <listitem>
          <para>Takes a qualified Varlink error name (i.e. an interface name, suffixed by an error name,
          separated by a dot; e.g. <literal>org.varlink.service.InvalidParameter</literal>). Ensures that if
          a method call fails with the specified error this will be treated as success, i.e. will cause the
          <command>varlinkctl</command> invocation to exit with a zero exit status. This option may be used more
          than once in order to treat multiple different errors as successes.</para>

          <xi:include href="version-info.xml" xpointer="v257"/>
        </listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="no-pager" />
      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <example>
      <title>Investigating a Service</title>

      <para>The following three commands inspect the <literal>io.systemd.Resolve</literal> service
      implemented by
      <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      listing general service information and implemented interfaces, and then displaying the interface
      definition of its primary interface:</para>

      <programlisting>$ varlinkctl info /run/systemd/resolve/io.systemd.Resolve
    Vendor: The systemd Project
   Product: systemd (systemd-resolved)
   Version: 254 (254-1522-g4790521^)
       URL: https://systemd.io/
Interfaces: io.systemd
            io.systemd.Resolve
            org.varlink.service
$ varlinkctl list-interfaces /run/systemd/resolve/io.systemd.Resolve
io.systemd
io.systemd.Resolve
org.varlink.service
$ varlinkctl introspect /run/systemd/resolve/io.systemd.Resolve io.systemd.Resolve
interface io.systemd.Resolve
type ResolvedAddress(
        ifindex: ?int,
        …</programlisting>

    <para>(Interface definition has been truncated in the example above, in the interest of brevity.)</para>
    </example>

    <example>
      <title>Invoking a Method</title>

      <para>The following command resolves a hostname via <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s <function>ResolveHostname</function>  method call.</para>

      <programlisting>$ varlinkctl call /run/systemd/resolve/io.systemd.Resolve io.systemd.Resolve.ResolveHostname '{"name":"systemd.io","family":2}' -j
{
        "addresses" : [
                {
                        "ifindex" : 2,
                        "family" : 2,
                        "address" : [
                                185,
                                199,
                                111,
                                153
                        ]
                }
        ],
        "name" : "systemd.io",
        "flags" : 1048577
}</programlisting>
    </example>

    <example>
      <title>Investigating a Service Executable</title>

      <para>The following command inspects the <filename>/usr/lib/systemd/systemd-pcrextend</filename>
      executable and the IPC APIs it provides. It then invokes a method on it:</para>

      <programlisting># varlinkctl info /usr/lib/systemd/systemd-pcrextend
    Vendor: The systemd Project
   Product: systemd (systemd-pcrextend)
   Version: 254 (254-1536-g97734fb)
       URL: https://systemd.io/
Interfaces: io.systemd
            io.systemd.PCRExtend
            org.varlink.service
# varlinkctl introspect /usr/lib/systemd/systemd-pcrextend io.systemd.PCRExtend
interface io.systemd.PCRExtend

method Extend(
        pcr: int,
        text: ?string,
        data: ?string
) -> ()
# varlinkctl call /usr/lib/systemd/systemd-pcrextend io.systemd.PCRExtend.Extend '{"pcr":15,"text":"foobar"}'
{}</programlisting>
    </example>

    <example>
      <title>Invoking a method remotely via SSH</title>

      <para>The following command acquires a report about the identity of a remote host
      <literal>somehost</literal> from
      <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      by connecting via SSH to the <constant>AF_UNIX</constant> socket the service listens on:</para>

      <programlisting># varlinkctl call ssh-unix:somehost:/run/systemd/io.systemd.Hostname io.systemd.Hostname.Describe '{}'</programlisting>

      <para>To invoke a Varlink service binary directly on the remote host, rather than talking to a service
      via <constant>AF_UNIX</constant> can be done like this:</para>

      <programlisting># varlinkctl call ssh-exec:somehost:/usr/bin/systemd-creds org.varlink.service.GetInfo '{}'</programlisting>
    </example>

  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><ulink url="https://varlink.org/">Varlink</ulink></member>
    </simplelist></para>
  </refsect1>
</refentry>