<?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"> <!-- This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <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 <constant>AF_UNIX</constant> <constant>SOCK_DGRAM</constant> 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 must be used after <filename>/var/</filename> is mounted, as otherwise log data from <filename>/run</filename> is never flushed to <filename>/var</filename> regardless of the configuration.</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 overridden on the kernel command line:</para> <variablelist class='kernel-commandline-options'> <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>Access Control</title> <para>Journal files are, by default, owned and readable by the <literal>systemd-journal</literal> system group but are not writable. Adding a user to this group thus enables her/him to read the journal files.</para> <para>By default, each logged in user will get her/his own set of journal files in <filename>/var/log/journal/</filename>. These files will not be owned by the user, however, in order to avoid that the user can write to them directly. Instead, file system ACLs are used to ensure the user gets read access only.</para> <para>Additional users and groups may be granted access to journal files via file system access control lists (ACL). Distributions and administrators may choose to grant read access to all members of the <literal>wheel</literal> and <literal>adm</literal> system groups with a command such as the following:</para> <programlisting># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/</programlisting> <para>Note that this command will update the ACLs both for existing journal files and for future journal files created in the <filename>/var/log/journal/</filename> directory.</para> </refsect1> <refsect1> <title>Files</title> <variablelist> <varlistentry> <term><filename>/etc/systemd/journald.conf</filename></term> <listitem><para>Configure <command>systemd-journald</command> behaviour. See <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. </para></listitem> </varlistentry> <varlistentry> <term><filename>/run/log/journal/<replaceable>machine-id</replaceable>/*.journal</filename></term> <term><filename>/run/log/journal/<replaceable>machine-id</replaceable>/*.journal~</filename></term> <term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal</filename></term> <term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal~</filename></term> <listitem><para><command>systemd-journald</command> writes entries to files in <filename>/run/log/journal/<replaceable>machine-id</replaceable>/</filename> or <filename>/var/log/journal/<replaceable>machine-id</replaceable>/</filename> with the <literal>.journal</literal> suffix. If the daemon is stopped uncleanly, or if the files are found to be corrupted, they are renamed using the <literal>.journal~</literal> suffix, and <command>systemd-journald</command> starts writing to a new file. <filename>/run</filename> is used when <filename>/var/log/journal</filename> is not available, or when <option>Storage=volatile</option> is set in the <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> configuration file. </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>, <citerefentry><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <command>pydoc systemd.journal</command>. </para> </refsect1> </refentry>