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<refentry id="systemd-journald.service">

<refentryinfo>

<title>systemd-journald.service</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-journald.service</refentrytitle>

<manvolnum>8</manvolnum>

</refmeta>

<refnamediv>

<refname>systemd-journald.service</refname>

<refname>systemd-journald.socket</refname>

<refname>systemd-journald</refname>

<refpurpose>Journal service</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename>systemd-journald.service</filename></para>

<para><filename>systemd-journald.socket</filename></para>

<para><filename>/usr/lib/systemd/systemd-journald</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><filename>systemd-journald</filename> is a

system service that collects and stores logging

data. It creates and maintains structured, indexed

journals based on logging information that is received

from the kernel, from user processes via the libc

<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>

call, from STDOUT/STDERR of system services or via its

native API. It will implicitly collect numerous meta

data fields for each log messages in a secure and

unfakeable way. See

<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>

for more information about the collected meta data.

</para>

<para>Log data collected by the journal is primarily

text based but can also include binary data where

necessary. All objects stored in the journal can be up

to 2^64-1 bytes in size.</para>

<para>By default the journal stores log data in

<filename>/run/log/journal/</filename>. Since

<filename>/run/</filename> is volatile log data is

lost at reboot. To make the data persistent it

is sufficient to create

<filename>/var/log/journal/</filename> where

<filename>systemd-journald</filename> will then store

the data.</para>

<para><filename>systemd-journald</filename> will

forward all received log messages to the AF_UNIX

SOCK_DGRAM socket

<filename>/run/systemd/journal/syslog</filename> (if it exists) which

may be used by UNIX syslog daemons to process the data

further.</para>

<para>See

<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for information about the configuration of this

service.</para>

</refsect1>

<refsect1>

<title>Signals</title>

<variablelist>

<varlistentry>

<term>SIGUSR1</term>

<listitem><para>Request that journal

data from <filename>/run/</filename>

is flushed to

<filename>/var/</filename> in order to

make it persistent (if this is

enabled). This may be used after

<filename>/var/</filename> is mounted,

but is generally not required since

the first journal write when

<filename>/var/</filename> becomes

writable triggers the flushing

anyway.</para></listitem>

</varlistentry>

<varlistentry>

<term>SIGUSR2</term>

<listitem><para>Request immediate

rotation of the journal

files.</para></listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>Kernel Command Line</title>

<para>A few configuration parameters from

<filename>journald.conf</filename> may be overriden on

the kernel command line:</para>

<variablelist>

<varlistentry>

<term><varname>systemd.journald.forward_to_syslog=</varname></term>

<term><varname>systemd.journald.forward_to_kmsg=</varname></term>

<term><varname>systemd.journald.forward_to_console=</varname></term>

<listitem><para>Enables/disables

forwarding of collected log messages

to syslog, the kernel log buffer or

the system console.

</para>

<para>See

<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for information about these settings.</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>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>