systemd/man/org.freedesktop.LogControl1.xml

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  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" >
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="org.freedesktop.LogControl1"
    xmlns:xi="http://www.w3.org/2001/XInclude">
  <refentryinfo>
    <title>org.freedesktop.LogControl1</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>org.freedesktop.LogControl1</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>org.freedesktop.LogControl1</refname>
    <refpurpose>D-Bus interface to query and set logging configuration</refpurpose>
  </refnamediv>

  <refsect1>
    <title>Introduction</title>

    <para><interfacename>org.freedesktop.LogControl1</interfacename> is a generic interface that is intended
    to be used by any daemon which allows the log level and target to be set over D-Bus. It is implemented by
    various daemons that are part of the
    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> suite.</para>

    <para>It is assumed that those settings are global for the whole program, so a fixed object path is
    used. The interface should always be available under the path
    <filename>/org/freedesktop/LogControl1</filename>.</para>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>The following interface is exposed:</para>

    <programlisting executable="systemd" node="/org/freedesktop/LogControl1" interface="org.freedesktop.LogControl1">
node /org/freedesktop/LogControl1 {
  interface org.freedesktop.LogControl1 {
    properties:
      @org.freedesktop.DBus.Property.EmitsChangedSignal("false")
      @org.freedesktop.systemd1.Privileged("true")
      readwrite s LogLevel = '...';
      @org.freedesktop.DBus.Property.EmitsChangedSignal("false")
      @org.freedesktop.systemd1.Privileged("true")
      readwrite s LogTarget = '...';
      @org.freedesktop.DBus.Property.EmitsChangedSignal("false")
      readonly s SyslogIdentifier = '...';
  };
  interface org.freedesktop.DBus.Peer { ... };
  interface org.freedesktop.DBus.Introspectable { ... };
  interface org.freedesktop.DBus.Properties { ... };
};
    </programlisting>

    <!--Autogenerated cross-references for systemd.directives, do not edit-->

    <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.LogControl1"/>

    <variablelist class="dbus-interface" generated="True" extra-ref="org.freedesktop.LogControl1"/>

    <variablelist class="dbus-property" generated="True" extra-ref="LogLevel"/>

    <variablelist class="dbus-property" generated="True" extra-ref="LogTarget"/>

    <variablelist class="dbus-property" generated="True" extra-ref="SyslogIdentifier"/>

    <!--End of Autogenerated section-->

    <refsect2>
      <title>Properties</title>

      <para><varname>LogLevel</varname> describes the
      <citerefentry project="man-pages"><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>-style
      log-level, and should be one of <literal>emerg</literal>, <literal>alert</literal>,
      <literal>crit</literal>, <literal>err</literal>, <literal>warning</literal>, <literal>notice</literal>,
      <literal>info</literal>, <literal>debug</literal>, in order of increasing verbosity.</para>

      <para><varname>LogTarget</varname> describes the log target (mechanism). It should be one of
      <literal>console</literal> (log to the console or standard output),
      <literal>kmsg</literal> (log to the kernel ring buffer),
      <literal>journal</literal> (log to the journal natively, see
      <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>),
      <literal>syslog</literal> (log using the
      <citerefentry project="man-pages"><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> call).
      </para>

      <para>Those two properties are writable, so they may be set by sufficiently privileged users.</para>

      <para><varname>SyslogIdentifier</varname> is a read-only property that shows the "syslog identifier".
      It is a short string that identifies the program that is the source of log messages that is passed to
      the <citerefentry project="man-pages"><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> call.
      </para>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Tools</title>

    <para><command>journalctl</command> option <option>-p</option>/<option>--priority=</option> may be used
    to filter log messages by log level, option <option>-t</option>/<option>--identifier=</option> may be
    used to by the syslog identifier, and filters like <literal>_TRANSPORT=syslog</literal>,
    <literal>_TRANSPORT=journal</literal>, and <literal>_TRANSPORT=kernel</literal> may be used to filter
    messages by the mechanism through which they reached <command>systemd-journald</command>.</para>

    <para><command>systemctl log-level</command> and <command>systemctl log-target</command> verbs may be
    used to query and set the <varname>LogLevel</varname> and <varname>LogTarget</varname> properties of the
    service manager. <command>systemctl service-log-level</command> and <command>systemctl
    service-log-target</command> may similarly be used for individual services. (Services must have the
    <varname>BusName=</varname> property set and must implement the interface described here. See
    <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for details about <varname>BusName=</varname>.)</para>
  </refsect1>

  <refsect1>
    <title>Example</title>

    <example>
      <title>Create a simple listener on the bus that implements LogControl1</title>

      <programlisting><xi:include href="logcontrol-example.c" parse="text"/></programlisting>

      <para>This creates a simple server on the bus. It implements the LogControl1 interface by providing
      the required properties and allowing to set the writable ones. It logs at the configured log level using
      <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
    </example>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry project="man-pages"><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>
</refentry>