+ <term><varname>_KERNEL_DEVICE=</varname></term>
+ <listitem>
+ <para>The kernel device
+ name. If the entry is
+ associated to a block device,
+ the major and minor of the
+ device node, separated by <literal>:</literal>
+ and prefixed by <literal>b</literal>. Similar
+ for character devices, but
+ prefixed by <literal>c</literal>. For network
+ devices the interface index,
+ prefixed by <literal>n</literal>. For all other
+ devices <literal>+</literal> followed by the
+ subsystem name, followed by
+ <literal>:</literal>, followed by the kernel
+ device name.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
+ <listitem>
+ <para>The kernel subsystem name.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>_UDEV_SYSNAME=</varname></term>
+ <listitem>
+ <para>The kernel device name
+ as it shows up in the device
+ tree below
+ <filename>/sys</filename>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>_UDEV_DEVNODE=</varname></term>
+ <listitem>
+ <para>The device node path of
+ this device in
+ <filename>/dev</filename>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>_UDEV_DEVLINK=</varname></term>
+ <listitem>
+ <para>Additional symlink names
+ pointing to the device node in
+ <filename>/dev</filename>. This
+ field is frequently set more
+ than once per entry.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Fields to log on behalf of a different program</title>
+
+ <para>Fields in this section are used by programs
+ to specify that they are logging on behalf of another
+ program or unit.
+ </para>
+
+ <para>Fields used by the <command>systemd-coredump</command>
+ coredump kernel helper:
+ </para>
+
+ <variablelist class='journal-directives'>
+ <varlistentry>
+ <term><varname>COREDUMP_UNIT=</varname></term>
+ <term><varname>COREDUMP_USER_UNIT=</varname></term>
+ <listitem>
+ <para>Used to annotate
+ messages containing coredumps from
+ system and session units.
+ See
+ <citerefentry><refentrytitle>systemd-coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Priviledged programs (currently UID 0) may
+ attach <varname>OBJECT_PID=</varname> to a
+ message. This will instruct
+ <command>systemd-journald</command> to attach
+ additional fields on behalf of the caller:</para>
+
+ <variablelist class='journal-directives'>
+ <varlistentry>
+ <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
+ <listitem>
+ <para>PID of the program that this
+ message pertains to.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>OBJECT_UID=</varname></term>
+ <term><varname>OBJECT_GID=</varname></term>
+ <term><varname>OBJECT_COMM=</varname></term>
+ <term><varname>OBJECT_EXE=</varname></term>
+ <term><varname>OBJECT_CMDLINE=</varname></term>
+ <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
+ <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
+ <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
+ <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
+ <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
+ <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
+ <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
+ <listitem>
+ <para>These are additional fields added automatically
+ by <command>systemd-journald</command>.
+ Their meaning is the same as
+ <varname>_UID=</varname>,
+ <varname>_GID=</varname>,
+ <varname>_COMM=</varname>,
+ <varname>_EXE=</varname>,
+ <varname>_CMDLINE=</varname>,
+ <varname>_AUDIT_SESSION=</varname>,
+ <varname>_AUDIT_LOGINUID=</varname>,
+ <varname>_SYSTEMD_CGROUP=</varname>,
+ <varname>_SYSTEMD_SESSION=</varname>,
+ <varname>_SYSTEMD_UNIT=</varname>,
+ <varname>_SYSTEMD_USER_UNIT=</varname>, and
+ <varname>_SYSTEMD_OWNER_UID=</varname>
+ as described above, except that the
+ process identified by <replaceable>PID</replaceable>
+ is described, instead of the process
+ which logged the message.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+
+ </refsect1>
+
+ <refsect1>
+ <title>Address Fields</title>
+
+ <para>During serialization into external formats, such
+ as the <ulink
+ url="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
+ Export Format</ulink> or the <ulink
+ url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
+ JSON Format</ulink>, the addresses of journal entries
+ are serialized into fields prefixed with double
+ underscores. Note that these are not proper fields when
+ stored in the journal but for addressing meta data of
+ entries. They cannot be written as part of structured
+ log entries via calls such as
+ <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>. They
+ may also not be used as matches for
+ <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
+
+ <variablelist class='journal-directives'>
+ <varlistentry>
+ <term><varname>__CURSOR=</varname></term>