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258 lines
13 KiB
XML
258 lines
13 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd-journald.service">
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<refentryinfo>
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<title>systemd-journald.service</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-journald.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-journald.service</refname>
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<refname>systemd-journald.socket</refname>
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<refname>systemd-journald-dev-log.socket</refname>
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<refname>systemd-journald</refname>
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<refpurpose>Journal service</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-journald.service</filename></para>
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<para><filename>systemd-journald.socket</filename></para>
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<para><filename>systemd-journald-dev-log.socket</filename></para>
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<para><filename>/usr/lib/systemd/systemd-journald</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-journald</filename> is a
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system service that collects and stores logging data.
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It creates and maintains structured, indexed journals
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based on logging information that is received from the
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kernel, from user processes via the libc
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<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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call, from standard input and standard error of system
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services or via its native API. It will implicitly
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collect numerous metadata fields for each log
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messages in a secure and unfakeable way. See
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information about the collected metadata.
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</para>
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<para>Log data collected by the journal is primarily
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text-based but can also include binary data where
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necessary. All objects stored in the journal can be up
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to 2^64-1 bytes in size.</para>
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<para>By default, the journal stores log data in
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<filename>/run/log/journal/</filename>. Since
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<filename>/run/</filename> is volatile, log data is
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lost at reboot. To make the data persistent, it
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is sufficient to create
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<filename>/var/log/journal/</filename> where
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<filename>systemd-journald</filename> will then store
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the data.</para>
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<para><filename>systemd-journald</filename> will
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forward all received log messages to the <constant>AF_UNIX</constant>
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<constant>SOCK_DGRAM</constant> socket
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<filename>/run/systemd/journal/syslog</filename>, if it exists, which
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may be used by Unix syslog daemons to process the data
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further.</para>
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<para>See
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information about the configuration of this
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service.</para>
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</refsect1>
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<refsect1>
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<title>Signals</title>
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<variablelist>
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<varlistentry>
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<term>SIGUSR1</term>
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<listitem><para>Request that journal
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data from <filename>/run/</filename>
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is flushed to
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<filename>/var/</filename> in order to
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make it persistent (if this is
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enabled). This must be used after
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<filename>/var/</filename> is mounted,
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as otherwise log data from
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<filename>/run</filename> is never
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flushed to <filename>/var</filename>
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regardless of the
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configuration.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>SIGUSR2</term>
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<listitem><para>Request immediate
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rotation of the journal
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files.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para>A few configuration parameters from
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<filename>journald.conf</filename> may be overridden on
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the kernel command line:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.journald.forward_to_syslog=</varname></term>
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<term><varname>systemd.journald.forward_to_kmsg=</varname></term>
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<term><varname>systemd.journald.forward_to_console=</varname></term>
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<term><varname>systemd.journald.forward_to_wall=</varname></term>
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<listitem><para>Enables/disables
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forwarding of collected log messages
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to syslog, the kernel log buffer, the
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system console or wall.
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</para>
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<para>See
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information about these settings.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Access Control</title>
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<para>Journal files are, by default, owned and readable
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by the <literal>systemd-journal</literal> system group
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but are not writable. Adding a user to this group thus
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enables her/him to read the journal files.</para>
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<para>By default, each logged in user will get her/his
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own set of journal files in
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<filename>/var/log/journal/</filename>. These files
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will not be owned by the user, however, in order to
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avoid that the user can write to them
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directly. Instead, file system ACLs are used to ensure
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the user gets read access only.</para>
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<para>Additional users and groups may be granted
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access to journal files via file system access control
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lists (ACL). Distributions and administrators may
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choose to grant read access to all members of the
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<literal>wheel</literal> and <literal>adm</literal>
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system groups with a command such as the
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following:</para>
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<programlisting># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/</programlisting>
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<para>Note that this command will update the ACLs both
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for existing journal files and for future journal
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files created in the
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<filename>/var/log/journal/</filename>
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directory.</para>
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</refsect1>
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<refsect1>
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<title>Files</title>
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<variablelist>
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<varlistentry>
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<term><filename>/etc/systemd/journald.conf</filename></term>
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<listitem><para>Configure
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<command>systemd-journald</command>
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behaviour. See
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>/run/log/journal/<replaceable>machine-id</replaceable>/*.journal</filename></term>
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<term><filename>/run/log/journal/<replaceable>machine-id</replaceable>/*.journal~</filename></term>
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<term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal</filename></term>
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<term><filename>/var/log/journal/<replaceable>machine-id</replaceable>/*.journal~</filename></term>
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<listitem><para><command>systemd-journald</command>
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writes entries to files in
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<filename>/run/log/journal/<replaceable>machine-id</replaceable>/</filename>
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or
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<filename>/var/log/journal/<replaceable>machine-id</replaceable>/</filename>
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with the <literal>.journal</literal>
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suffix. If the daemon is stopped
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uncleanly, or if the files are found
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to be corrupted, they are renamed
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using the <literal>.journal~</literal>
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suffix, and
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<command>systemd-journald</command>
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starts writing to a new
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file. <filename>/run</filename> is
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used when
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<filename>/var/log/journal</filename>
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is not available, or when
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<option>Storage=volatile</option> is
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set in the
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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configuration file.
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</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-coredump</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<command>pydoc systemd.journal</command>.
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</para>
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</refsect1>
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</refentry>
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