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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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Copyright 2010 Lennart Poettering
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<refentry id="systemd.journal-fields">
<refentryinfo>
<title>systemd.journal-fields</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.journal-fields</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.journal-fields</refname>
<refpurpose>Special journal fields</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>Entries in the journal resemble an environment block in
their syntax but with fields that can include binary data.
Primarily, fields are formatted UTF-8 text strings, and binary
formatting is used only where formatting as UTF-8 text strings
makes little sense. New fields may freely be defined by
applications, but a few fields have special meaning. All fields
with special meanings are optional. In some cases, fields may
appear more than once per entry.</para>
</refsect1>
<refsect1>
<title>User Journal Fields</title>
<para>User fields are fields that are directly passed from clients
and stored in the journal.</para>
<variablelist class='journal-directives'>
<varlistentry>
<term><varname>MESSAGE=</varname></term>
<listitem>
<para>The human-readable message string for this entry. This
is supposed to be the primary text shown to the user. It is
usually not translated (but might be in some cases), and is
not supposed to be parsed for meta data.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>MESSAGE_ID=</varname></term>
<listitem>
<para>A 128-bit message identifier ID for recognizing
certain message types, if this is desirable. This should
contain a 128-bit ID formatted as a lower-case hexadecimal
string, without any separating dashes or suchlike. This is
recommended to be a UUID-compatible ID, but this is not
enforced, and formatted differently. Developers can generate
a new ID for this purpose with <command>journalctl
<option>--new-id</option></command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PRIORITY=</varname></term>
<listitem>
<para>A priority value between 0 (<literal>emerg</literal>)
and 7 (<literal>debug</literal>) formatted as a decimal
string. This field is compatible with syslog's priority
concept.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>CODE_FILE=</varname></term>
<term><varname>CODE_LINE=</varname></term>
<term><varname>CODE_FUNC=</varname></term>
<listitem>
<para>The code location generating this message, if known.
Contains the source filename, the line number and the
function name.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ERRNO=</varname></term>
<listitem>
<para>The low-level Unix error number causing this entry, if
any. Contains the numeric value of
<citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
formatted as a decimal string.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SYSLOG_FACILITY=</varname></term>
<term><varname>SYSLOG_IDENTIFIER=</varname></term>
<term><varname>SYSLOG_PID=</varname></term>
<listitem>
<para>Syslog compatibility fields containing the facility
(formatted as decimal string), the identifier string (i.e.
"tag"), and the client PID. (Note that the tag is usually
derived from glibc's
<varname>program_invocation_short_name</varname> variable,
see
<citerefentry project='die-net'><refentrytitle>program_invocation_short_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.)</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Trusted Journal Fields</title>
<para>Fields prefixed with an underscore are trusted fields, i.e.
fields that are implicitly added by the journal and cannot be
altered by client code.</para>
<variablelist class='journal-directives'>
<varlistentry>
<term><varname>_PID=</varname></term>
<term><varname>_UID=</varname></term>
<term><varname>_GID=</varname></term>
<listitem>
<para>The process, user, and group ID of the process the
journal entry originates from formatted as a decimal
string.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_COMM=</varname></term>
<term><varname>_EXE=</varname></term>
<term><varname>_CMDLINE=</varname></term>
<listitem>
<para>The name, the executable path, and the command line of
the process the journal entry originates from.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_CAP_EFFECTIVE=</varname></term>
<listitem>
<para>The effective
<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
of the process the journal entry originates from.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_AUDIT_SESSION=</varname></term>
<term><varname>_AUDIT_LOGINUID=</varname></term>
<listitem>
<para>The session and login UID of the process the journal
entry originates from, as maintained by the kernel audit
subsystem.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_SYSTEMD_CGROUP=</varname></term>
<term><varname>_SYSTEMD_SESSION=</varname></term>
<term><varname>_SYSTEMD_UNIT=</varname></term>
<term><varname>_SYSTEMD_USER_UNIT=</varname></term>
<term><varname>_SYSTEMD_OWNER_UID=</varname></term>
<term><varname>_SYSTEMD_SLICE=</varname></term>
<listitem>
<para>The control group path in the systemd hierarchy, the
systemd session ID (if any), the systemd unit name (if any),
the systemd user session unit name (if any), the owner UID
of the systemd session (if any) and the systemd slice unit
of the process the journal entry originates from.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_SELINUX_CONTEXT=</varname></term>
<listitem>
<para>The SELinux security context (label) of the process
the journal entry originates from.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
<listitem>
<para>The earliest trusted timestamp of the message, if any
is known that is different from the reception time of the
journal. This is the time in microseconds since the epoch
UTC, formatted as a decimal string.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_BOOT_ID=</varname></term>
<listitem>
<para>The kernel boot ID for the boot the message was
generated in, formatted as a 128-bit hexadecimal
string.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_MACHINE_ID=</varname></term>
<listitem>
<para>The machine ID of the originating host, as available
in
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_HOSTNAME=</varname></term>
<listitem>
<para>The name of the originating host.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>_TRANSPORT=</varname></term>
<listitem>
<para>How the entry was received by the journal service.
Valid transports are:
</para>
<variablelist>
<varlistentry>
<term>
<option>driver</option>
</term>
<listitem>
<para>for internally generated messages
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>syslog</option>
</term>
<listitem>
<para>for those received via the local syslog socket
with the syslog protocol
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>journal</option>
</term>
<listitem>
<para>for those received via the native journal
protocol
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>stdout</option>
</term>
<listitem>
<para>for those read from a service's standard output
or error output
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<option>kernel</option>
</term>
<listitem>
<para>for those read from the kernel
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Kernel Journal Fields</title>
<para>Kernel fields are fields that are used by messages
originating in the kernel and stored in the journal.</para>
<variablelist class='journal-directives'>
<varlistentry>
<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, this
is the interface index prefixed by <literal>n</literal>. For
all other devices, this is the subsystem name prefixed by
<literal>+</literal>, 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>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>Privileged 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 metadata 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>
<listitem>
<para>The cursor for the entry. A cursor is an opaque text
string that uniquely describes the position of an entry in
the journal and is portable across machines, platforms and
journal files.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>__REALTIME_TIMESTAMP=</varname></term>
<listitem>
<para>The wallclock time
(<constant>CLOCK_REALTIME</constant>) at the point in time
the entry was received by the journal, in microseconds since
the epoch UTC, formatted as a decimal string. This has
different properties from
<literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
usually a bit later but more likely to be monotonic.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
<listitem>
<para>The monotonic time
(<constant>CLOCK_MONOTONIC</constant>) at the point in time
the entry was received by the journal in microseconds,
formatted as a decimal string. To be useful as an address
for the entry, this should be combined with the boot ID in
<literal>_BOOT_ID=</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
</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>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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