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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, however with fields that can
include binary data. Primarily, fields are formatted
ASCII strings, and binary formatting is used only
where formatting as ASCII makes little sense. New
fields may be freely defined by applications, but a
few fields have special meaning. All fields with
special meaning are optional.</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 >
<varlistentry >
<term > MESSAGE=</term>
<listitem >
<para > The human readable
message string for this
entry. This is supposed to be
the primary text shown to the
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user. It is usually not
translated (but might be in
some cases), and is not
supposed to be parsed for meta
data.</para>
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</listitem>
</varlistentry>
<varlistentry >
<term > MESSAGE_ID=</term>
<listitem >
<para > A 128bit message
identifier ID for recognizing
certain message types, if this
is desirable. This should
contain a 128bit id formatted
as 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
--new-id</command> .</para>
</listitem>
</varlistentry>
<varlistentry >
<term > PRIORITY=</term>
<listitem >
<para > A priority value between
0 (<literal > emerg</literal> )
and 7
(<literal > debug</literal> )
formatted as decimal
string. This field is
compatible with syslog's
priority concept.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > CODE_FILE=</term>
<term > CODE_LINE=</term>
<term > CODE_FUNC=</term>
<listitem >
<para > The code location
generating this message, if
known. Contains the source
file name, the line number and
the function name.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > SYSLOG_FACILITY=</term>
<term > SYSLOG_IDENTIFIER=</term>
<term > SYSLOG_PID=</term>
<listitem >
<para > Syslog compatibility
fields containing the facility
(formatted as decimal string),
the identifier string
(i.e. "tag"), and the client
PID.</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 >
<varlistentry >
<term > _PID=</term>
<term > _UID=</term>
<term > _GID=</term>
<listitem >
<para > The process, user and
group ID of the process the
journal entry originates from
formatted as decimal
string.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > _COMM=</term>
<term > _EXE=</term>
<term > _CMDLINE=</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 > _AUDIT_SESSION=</term>
<term > _AUDIT_LOGINUID=</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 > _SYSTEMD_CGROUP=</term>
<term > _SYSTEMD_SESSION=</term>
<term > _SYSTEMD_UNIT=</term>
<term > _SYSTEMD_OWNER_UID=</term>
<listitem >
<para > The contol group path in
the systemd hierarchy, the
systemd session ID (if any),
the systemd unit name (if any)
and the owner UID of the
systemd session (if any) of
the process the journal entry
originates from.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > _SELINUX_CONTEXT=</term>
<listitem >
<para > The SELinux security
context of the process the
journal entry originates
from.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > _SOURCE_REALTIME_TIMESTAMP=</term>
<listitem >
<para > The earliest trusted
timestamp of the message, if
any is known that is different
from the reception time of the
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journal. This is the time in
usec since the epoch UTC
formatted as decimal
string.</para>
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</listitem>
</varlistentry>
<varlistentry >
<term > _BOOT_ID=</term>
<listitem >
<para > The kernel boot ID for
the boot the message was
generated in, formatted as
128bit hexadecimal
string.</para>
</listitem>
</varlistentry>
<varlistentry >
<term > _MACHINE_ID=</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 > _HOSTNAME=</term>
<listitem >
<para > The name of the
originating host.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > _TRANSPORT=</term>
<listitem >
<para > How the entry was
received by the journal
service. One of
<literal > driver</literal> ,
<literal > syslog</literal> ,
<literal > journal</literal> ,
<literal > stdout</literal> ,
<literal > kernel</literal> for
internally generated messages,
for those received via the
local syslog socket with the
syslog protocol, for those
received via the native
journal protocol, for the
those read from a services'
standard output or error
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output, and for those read
from the kernel, resp.
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</para>
</listitem>
</varlistentry>
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</variablelist>
</refsect1>
<refsect1 >
<title > Address Fields</title>
<para > During serialization into external formats the
addresses of journal entries are serialized into
fields prefixed with double underscores. Note that
these aren't proper fields when stored in the journal,
but addressing meta data of entries.</para>
<variablelist >
<varlistentry >
<term > __CURSOR=</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 > __REALTIME_TIMESTAMP=</term>
<listitem >
<para > The wallclock time
(CLOCK_REALTIME) at the point
in time the entry was received
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by the journal, in usec since
the epoch UTC formatted as
decimal string. This has
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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 > __MONOTONIC_TIMESTAMP=</term>
<listitem >
<para > The monotonic time
(CLOCK_MONOTONIC) at the point
in time the entry was received
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by the journal in usec
formatted as decimal
string. To be useful as an
address for the entry this
should be combined with with
boot ID in
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<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>
</para>
</refsect1>
</refentry>
