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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
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block in their syntax but with fields that can
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include binary data. Primarily, fields are formatted
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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
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optional. In some cases, fields may appear more than
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once per entry.</para>
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</refsect1>
<refsect1 >
<title > User Journal Fields</title>
<para > User fields are fields that are directly passed
from clients and stored in the journal.</para>
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<variablelist class= 'journal-directives' >
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<varlistentry >
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<term > <varname > MESSAGE=</varname> </term>
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<listitem >
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<para > The human-readable
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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 >
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<term > <varname > MESSAGE_ID=</varname> </term>
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<listitem >
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<para > A 128-bit message
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identifier ID for recognizing
certain message types, if this
is desirable. This should
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contain a 128-bit ID formatted
as a lower-case hexadecimal
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string, without any separating
dashes or suchlike. This is
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recommended to be a
UUID-compatible ID, but this is not
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enforced, and formatted
differently. Developers can
generate a new ID for this
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purpose with <command > journalctl
<option > --new-id</option> </command> .
</para>
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</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > PRIORITY=</varname> </term>
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<listitem >
<para > A priority value between
0 (<literal > emerg</literal> )
and 7
(<literal > debug</literal> )
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formatted as a decimal
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string. This field is
compatible with syslog's
priority concept.</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > CODE_FILE=</varname> </term>
<term > <varname > CODE_LINE=</varname> </term>
<term > <varname > CODE_FUNC=</varname> </term>
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<listitem >
<para > The code location
generating this message, if
known. Contains the source
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filename, the line number and
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the function name.</para>
</listitem>
</varlistentry>
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<varlistentry >
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<term > <varname > ERRNO=</varname> </term>
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<listitem >
<para > The low-level Unix error
number causing this entry, if
any. Contains the numeric
value of
<citerefentry > <refentrytitle > errno</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
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formatted as a decimal
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string.</para>
</listitem>
</varlistentry>
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<varlistentry >
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<term > <varname > SYSLOG_FACILITY=</varname> </term>
<term > <varname > SYSLOG_IDENTIFIER=</varname> </term>
<term > <varname > SYSLOG_PID=</varname> </term>
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<listitem >
<para > Syslog compatibility
fields containing the facility
(formatted as decimal string),
the identifier string
(i.e. "tag"), and the client
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PID. (Note that the tag is
usually derived from glibc's
<varname > program_invocation_short_name</varname>
variable, see <citerefentry > <refentrytitle > program_invocation_short_name</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> .)</para>
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</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>
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<variablelist class= 'journal-directives' >
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<varlistentry >
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<term > <varname > _PID=</varname> </term>
<term > <varname > _UID=</varname> </term>
<term > <varname > _GID=</varname> </term>
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<listitem >
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<para > The process, user, and
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group ID of the process the
journal entry originates from
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formatted as a decimal
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string.</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _COMM=</varname> </term>
<term > <varname > _EXE=</varname> </term>
<term > <varname > _CMDLINE=</varname> </term>
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<listitem >
<para > The name, the executable
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path, and the command line of
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the process the journal entry
originates from.</para>
</listitem>
</varlistentry>
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<varlistentry >
<term > <varname > _CAP_EFFECTIVE=</varname> </term>
<listitem >
<para > The effective <citerefentry > <refentrytitle > capabilities</refentrytitle> <manvolnum > 7</manvolnum> </citerefentry> of
the process the journal entry
originates from.</para>
</listitem>
</varlistentry>
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<varlistentry >
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<term > <varname > _AUDIT_SESSION=</varname> </term>
<term > <varname > _AUDIT_LOGINUID=</varname> </term>
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<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 >
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<term > <varname > _SYSTEMD_CGROUP=</varname> </term>
<term > <varname > _SYSTEMD_SESSION=</varname> </term>
<term > <varname > _SYSTEMD_UNIT=</varname> </term>
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<term > <varname > _SYSTEMD_USER_UNIT=</varname> </term>
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<term > <varname > _SYSTEMD_OWNER_UID=</varname> </term>
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<term > <varname > _SYSTEMD_SLICE=</varname> </term>
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<listitem >
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<para > The control group path
in the systemd hierarchy, the
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systemd session ID (if any),
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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>
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</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _SELINUX_CONTEXT=</varname> </term>
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<listitem >
<para > The SELinux security
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context (label) of the process
the journal entry originates
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from.</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _SOURCE_REALTIME_TIMESTAMP=</varname> </term>
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<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
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microseconds since the epoch UTC,
formatted as a decimal
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string.</para>
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</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _BOOT_ID=</varname> </term>
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<listitem >
<para > The kernel boot ID for
the boot the message was
generated in, formatted as
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a 128-bit hexadecimal
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string.</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _MACHINE_ID=</varname> </term>
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<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 >
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<term > <varname > _HOSTNAME=</varname> </term>
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<listitem >
<para > The name of the
originating host.</para>
</listitem>
</varlistentry>
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<varlistentry >
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<term > <varname > _TRANSPORT=</varname> </term>
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<listitem >
<para > How the entry was
received by the journal
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service. Valid transports are:
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</para>
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<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>
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</listitem>
</varlistentry>
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</variablelist>
</refsect1>
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<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>
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<variablelist class= 'journal-directives' >
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<varlistentry >
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<term > <varname > _KERNEL_DEVICE=</varname> </term>
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<listitem >
<para > The kernel device
name. If the entry is
associated to a block device,
the major and minor of the
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device node, separated by <literal > :</literal>
and prefixed by <literal > b</literal> . Similar
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for character devices but
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prefixed by <literal > c</literal> . For network
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devices, this is the interface index
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prefixed by <literal > n</literal> . For all other
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devices, this is the subsystem name
prefixed by <literal > +</literal> , followed by
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<literal > :</literal> , followed by the kernel
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device name.</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _KERNEL_SUBSYSTEM=</varname> </term>
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<listitem >
<para > The kernel subsystem name.</para>
</listitem>
</varlistentry>
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<varlistentry >
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<term > <varname > _UDEV_SYSNAME=</varname> </term>
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<listitem >
<para > The kernel device name
as it shows up in the device
tree below
<filename > /sys</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _UDEV_DEVNODE=</varname> </term>
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<listitem >
<para > The device node path of
this device in
<filename > /dev</filename> .</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > _UDEV_DEVLINK=</varname> </term>
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<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>
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</variablelist>
</refsect1>
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<refsect1 >
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<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>
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<para > Fields used by the <command > systemd-coredump</command>
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coredump kernel helper:
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</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>
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<para > Priviledged programs (currently UID 0) may
attach <varname > OBJECT_PID=</varname> to a
message. This will instruct
<command > systemd-journald</command> to attach
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additional fields on behalf of the caller:</para>
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<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 >
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<para > These are additional fields added automatically
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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>
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as described above, except that the
process identified by <replaceable > PID</replaceable>
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is described, instead of the process
which logged the message.</para>
</listitem>
</varlistentry>
</variablelist>
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</refsect1>
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<refsect1 >
<title > Address Fields</title>
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<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
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underscores. Note that these are not proper fields when
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stored in the journal but for addressing metadata of
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entries. They cannot be written as part of structured
log entries via calls such as
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<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>
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<variablelist class= 'journal-directives' >
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<varlistentry >
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<term > <varname > __CURSOR=</varname> </term>
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<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,
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platforms and journal files.
</para>
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</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > __REALTIME_TIMESTAMP=</varname> </term>
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<listitem >
<para > The wallclock time
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(<constant > CLOCK_REALTIME</constant> )
at the point in time the entry
was received by the journal,
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in microseconds since the epoch
UTC, formatted as a decimal
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string. This has different
properties from
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<literal > _SOURCE_REALTIME_TIMESTAMP=</literal> ,
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as it is usually a bit later
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but more likely to be monotonic.
</para>
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</listitem>
</varlistentry>
<varlistentry >
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<term > <varname > __MONOTONIC_TIMESTAMP=</varname> </term>
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<listitem >
<para > The monotonic time
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(<constant > CLOCK_MONOTONIC</constant> )
at the point in time the entry
was received by the journal in
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microseconds, formatted as a decimal
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string. To be useful as an
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address for the entry, this
should be combined with with the
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boot ID in <literal > _BOOT_ID=</literal> .
</para>
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</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> ,
2012-07-09 17:46:21 +04:00
<citerefentry > <refentrytitle > journald.conf</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry> ,
2013-01-15 07:08:33 +04:00
<citerefentry > <refentrytitle > sd-journal</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
2013-02-07 09:50:37 +04:00
<citerefentry > <refentrytitle > systemd-coredumpctl</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> ,
2013-01-15 07:08:33 +04:00
<citerefentry > <refentrytitle > systemd.directives</refentrytitle> <manvolnum > 7</manvolnum> </citerefentry>
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</para>
</refsect1>
</refentry>
