systemd/man/journald.conf.xml

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<refentry id="journald.conf"
    xmlns:xi="http://www.w3.org/2001/XInclude">
  <refentryinfo>
    <title>journald.conf</title>
    <productname>systemd</productname>
  </refentryinfo>

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

  <refnamediv>
    <refname>journald.conf</refname>
    <refname>journald.conf.d</refname>
    <refpurpose>Journal service configuration files</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>/etc/systemd/journald.conf</filename></para>
    <para><filename>/etc/systemd/journald.conf.d/*.conf</filename></para>
    <para><filename>/run/systemd/journald.conf.d/*.conf</filename></para>
    <para><filename>/usr/lib/systemd/journald.conf.d/*.conf</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>These files configure various parameters of the systemd journal service,
    <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
    See
    <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for a general description of the syntax.</para>

  </refsect1>

  <xi:include href="standard-conf.xml" xpointer="main-conf" />

  <refsect1>
    <title>Options</title>

    <para>All options are configured in the
    <literal>[Journal]</literal> section:</para>

    <variablelist class='config-directives'>

      <varlistentry>
        <term><varname>Storage=</varname></term>

        <listitem><para>Controls where to store journal data. One of
        <literal>volatile</literal>,
        <literal>persistent</literal>,
        <literal>auto</literal> and
        <literal>none</literal>. If
        <literal>volatile</literal>, journal
        log data will be stored only in memory, i.e. below the
        <filename>/run/log/journal</filename> hierarchy (which is
        created if needed). If <literal>persistent</literal>, data
        will be stored preferably on disk, i.e. below the
        <filename>/var/log/journal</filename> hierarchy (which is
        created if needed), with a fallback to
        <filename>/run/log/journal</filename> (which is created if
        needed), during early boot and if the disk is not writable.
        <literal>auto</literal> is similar to
        <literal>persistent</literal> but the directory
        <filename>/var/log/journal</filename> is not created if
        needed, so that its existence controls where log data goes.
        <literal>none</literal> turns off all storage, all log data
        received will be dropped. Forwarding to other targets, such as
        the console, the kernel log buffer, or a syslog socket will
        still work however. Defaults to
        <literal>auto</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Compress=</varname></term>

        <listitem><para>Can take a boolean value. If enabled (the
        default), data objects that shall be stored in the journal
        and are larger than the default threshold of 512 bytes are
        compressed before they are written to the file system. It
        can also be set to a number of bytes to specify the
        compression threshold directly. Suffixes like K, M, and G
        can be used to specify larger units.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Seal=</varname></term>

        <listitem><para>Takes a boolean value. If enabled (the
        default), and a sealing key is available (as created by
        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
        <option>--setup-keys</option> command), Forward Secure Sealing
        (FSS) for all persistent journal files is enabled. FSS is
        based on <ulink
        url="https://eprint.iacr.org/2013/397">Seekable Sequential Key
        Generators</ulink> by G. A. Marson and B. Poettering
        (doi:10.1007/978-3-642-40203-6_7) and may be used to protect
        journal files from unnoticed alteration.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SplitMode=</varname></term>

        <listitem><para>Controls whether to split up journal files per user, either <literal>uid</literal> or
        <literal>none</literal>. Split journal files are primarily useful for access control: on UNIX/Linux access
        control is managed per file, and the journal daemon will assign users read access to their journal files. If
        <literal>uid</literal>, all regular users (with UID outside the range of system users, dynamic service users,
        and the nobody user) will each get their own journal files, and system users will log to the system journal.
        See <ulink url="https://systemd.io/UIDS-GIDS">Users, Groups, UIDs and GIDs on systemd systems</ulink>
        for more details about UID ranges.
        If <literal>none</literal>, journal files are not split up by user and all messages are
        instead stored in the single system journal. In this mode unprivileged users generally do not have access to
        their own log data. Note that splitting up journal files by user is only available for journals stored
        persistently. If journals are stored on volatile storage (see <varname>Storage=</varname> above), only a single
        journal file is used. Defaults to <literal>uid</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>RateLimitIntervalSec=</varname></term>
        <term><varname>RateLimitBurst=</varname></term>

        <listitem><para>Configures the rate limiting that is applied
        to all messages generated on the system. If, in the time
        interval defined by <varname>RateLimitIntervalSec=</varname>,
        more messages than specified in
        <varname>RateLimitBurst=</varname> are logged by a service,
        all further messages within the interval are dropped until the
        interval is over. A message about the number of dropped
        messages is generated. This rate limiting is applied
        per-service, so that two services which log do not interfere
        with each other's limits. Defaults to 10000 messages in 30s.
        The time specification for
        <varname>RateLimitIntervalSec=</varname> may be specified in the
        following units: <literal>s</literal>, <literal>min</literal>,
        <literal>h</literal>, <literal>ms</literal>,
        <literal>us</literal>. To turn off any kind of rate limiting,
        set either value to 0.</para>

        <para>Note that the effective rate limit is multiplied with a
        factor derived from the available free disk space for the journal.
        Currently, this factor is calculated using the base 2 logarithm.</para>

        <table>
          <title>Example <varname>RateLimitBurst=</varname> rate
            modifications by the available disk space</title>
          <tgroup cols='2'>
            <colspec colname='freespace' />
            <colspec colname='multiplier' />
            <thead>
              <row>
                <entry>Available Disk Space</entry>
                <entry>Burst Multiplier</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>&lt;= 1MB</entry>
                <entry>1</entry>
              </row>
              <row>
                <entry>&lt;= 16MB</entry>
                <entry>2</entry>
              </row>
              <row>
                <entry>&lt;= 256MB</entry>
                <entry>3</entry>
              </row>
              <row>
                <entry>&lt;= 4GB</entry>
                <entry>4</entry>
              </row>
              <row>
                <entry>&lt;= 64GB</entry>
                <entry>5</entry>
              </row>
              <row>
                <entry>&lt;= 1TB</entry>
                <entry>6</entry>
              </row>
            </tbody>
          </tgroup>
        </table>

        <para>If a service provides rate limits for itself through
        <varname>LogRateLimitIntervalSec=</varname> and/or <varname>LogRateLimitBurst=</varname>
        in <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        those values will override the settings specified here.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SystemMaxUse=</varname></term>
        <term><varname>SystemKeepFree=</varname></term>
        <term><varname>SystemMaxFileSize=</varname></term>
        <term><varname>SystemMaxFiles=</varname></term>
        <term><varname>RuntimeMaxUse=</varname></term>
        <term><varname>RuntimeKeepFree=</varname></term>
        <term><varname>RuntimeMaxFileSize=</varname></term>
        <term><varname>RuntimeMaxFiles=</varname></term>

        <listitem><para>Enforce size limits on the journal files
        stored. The options prefixed with <literal>System</literal>
        apply to the journal files when stored on a persistent file
        system, more specifically
        <filename>/var/log/journal</filename>. The options prefixed
        with <literal>Runtime</literal> apply to the journal files
        when stored on a volatile in-memory file system, more
        specifically <filename>/run/log/journal</filename>. The former
        is used only when <filename>/var</filename> is mounted,
        writable, and the directory
        <filename>/var/log/journal</filename> exists. Otherwise, only
        the latter applies. Note that this means that during early
        boot and if the administrator disabled persistent logging,
        only the latter options apply, while the former apply if
        persistent logging is enabled and the system is fully booted
        up. <command>journalctl</command> and
        <command>systemd-journald</command> ignore all files with
        names not ending with <literal>.journal</literal> or
        <literal>.journal~</literal>, so only such files, located in
        the appropriate directories, are taken into account when
        calculating current disk usage.</para>

        <para><varname>SystemMaxUse=</varname> and
        <varname>RuntimeMaxUse=</varname> control how much disk space
        the journal may use up at most.
        <varname>SystemKeepFree=</varname> and
        <varname>RuntimeKeepFree=</varname> control how much disk
        space systemd-journald shall leave free for other uses.
        <command>systemd-journald</command> will respect both limits
        and use the smaller of the two values.</para>

        <para>The first pair defaults to 10% and the second to 15% of
        the size of the respective file system, but each value is
        capped to 4G. If the file system is nearly full and either
        <varname>SystemKeepFree=</varname> or
        <varname>RuntimeKeepFree=</varname> are violated when
        systemd-journald is started, the limit will be raised to the
        percentage that is actually free. This means that if there was
        enough free space before and journal files were created, and
        subsequently something else causes the file system to fill up,
        journald will stop using more space, but it will not be
        removing existing files to reduce the footprint again,
        either. Also note that only archived files are deleted to reduce the
        space occupied by journal files. This means that, in effect, there might
        still be more space used than <varname>SystemMaxUse=</varname> or
        <varname>RuntimeMaxUse=</varname> limit after a vacuuming operation is
        complete.</para>

        <para><varname>SystemMaxFileSize=</varname> and
        <varname>RuntimeMaxFileSize=</varname> control how large
        individual journal files may grow at most. This influences
        the granularity in which disk space is made available through
        rotation, i.e. deletion of historic data. Defaults to one
        eighth of the values configured with
        <varname>SystemMaxUse=</varname> and
        <varname>RuntimeMaxUse=</varname>, so that usually seven
        rotated journal files are kept as history.</para>

        <para>Specify values in bytes or use K, M, G, T, P, E as
        units for the specified sizes (equal to 1024, 1024², … bytes).
        Note that size limits are enforced synchronously when journal
        files are extended, and no explicit rotation step triggered by
        time is needed.</para>

        <para><varname>SystemMaxFiles=</varname> and
        <varname>RuntimeMaxFiles=</varname> control how many
        individual journal files to keep at most. Note that only
        archived files are deleted to reduce the number of files until
        this limit is reached; active files will stay around. This
        means that, in effect, there might still be more journal files
        around in total than this limit after a vacuuming operation is
        complete. This setting defaults to 100.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MaxFileSec=</varname></term>

        <listitem><para>The maximum time to store entries in a single
        journal file before rotating to the next one. Normally,
        time-based rotation should not be required as size-based
        rotation with options such as
        <varname>SystemMaxFileSize=</varname> should be sufficient to
        ensure that journal files do not grow without bounds. However,
        to ensure that not too much data is lost at once when old
        journal files are deleted, it might make sense to change this
        value from the default of one month. Set to 0 to turn off this
        feature. This setting takes time values which may be suffixed
        with the units <literal>year</literal>,
        <literal>month</literal>, <literal>week</literal>,
        <literal>day</literal>, <literal>h</literal> or
        <literal>m</literal> to override the default time unit of
        seconds.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MaxRetentionSec=</varname></term>

        <listitem><para>The maximum time to store journal entries.
        This controls whether journal files containing entries older
        than the specified time span are deleted. Normally, time-based
        deletion of old journal files should not be required as
        size-based deletion with options such as
        <varname>SystemMaxUse=</varname> should be sufficient to
        ensure that journal files do not grow without bounds. However,
        to enforce data retention policies, it might make sense to
        change this value from the default of 0 (which turns off this
        feature). This setting also takes time values which may be
        suffixed with the units <literal>year</literal>,
        <literal>month</literal>, <literal>week</literal>,
        <literal>day</literal>, <literal>h</literal> or <literal>
        m</literal> to override the default time unit of
        seconds.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SyncIntervalSec=</varname></term>

        <listitem><para>The timeout before synchronizing journal files
        to disk. After syncing, journal files are placed in the
        OFFLINE state. Note that syncing is unconditionally done
        immediately after a log message of priority CRIT, ALERT or
        EMERG has been logged. This setting hence applies only to
        messages of the levels ERR, WARNING, NOTICE, INFO, DEBUG. The
        default timeout is 5 minutes. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ForwardToSyslog=</varname></term>
        <term><varname>ForwardToKMsg=</varname></term>
        <term><varname>ForwardToConsole=</varname></term>
        <term><varname>ForwardToWall=</varname></term>

        <listitem><para>Control whether log messages received by the journal daemon shall be forwarded to a
        traditional syslog daemon, to the kernel log buffer (kmsg), to the system console, or sent as wall
        messages to all logged-in users.  These options take boolean arguments. If forwarding to syslog is
        enabled but nothing reads messages from the socket, forwarding to syslog has no effect. By default,
        only forwarding to wall is enabled. These settings may be overridden at boot time with the kernel
        command line options <literal>systemd.journald.forward_to_syslog</literal>,
        <literal>systemd.journald.forward_to_kmsg</literal>,
        <literal>systemd.journald.forward_to_console</literal>, and
        <literal>systemd.journald.forward_to_wall</literal>. If the option name is specified without
        <literal>=</literal> and the following argument, true is assumed. Otherwise, the argument is parsed
        as a boolean.</para>

        <para>When forwarding to the console, the TTY to log to can be changed with
        <varname>TTYPath=</varname>, described below.</para>

        <para>When forwarding to the kernel log buffer (kmsg), make sure to select a suitably large size for
        the log buffer, and ensure the kernel's rate-limiting applied to userspace processes is turned
        off. Specifically, add <literal>log_buf_len=8M</literal> and <literal>printk.devkmsg=on</literal> (or
        similar) to the kernel command line.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MaxLevelStore=</varname></term>
        <term><varname>MaxLevelSyslog=</varname></term>
        <term><varname>MaxLevelKMsg=</varname></term>
        <term><varname>MaxLevelConsole=</varname></term>
        <term><varname>MaxLevelWall=</varname></term>

        <listitem><para>Controls the maximum log level of messages
        that are stored in the journal, forwarded to syslog, kmsg, the
        console or wall (if that is enabled, see above). As argument,
        takes one of
        <literal>emerg</literal>,
        <literal>alert</literal>,
        <literal>crit</literal>,
        <literal>err</literal>,
        <literal>warning</literal>,
        <literal>notice</literal>,
        <literal>info</literal>,
        <literal>debug</literal>,
        or integer values in the range of 0–7 (corresponding to the
        same levels). Messages equal or below the log level specified
        are stored/forwarded, messages above are dropped. Defaults to
        <literal>debug</literal> for <varname>MaxLevelStore=</varname>
        and <varname>MaxLevelSyslog=</varname>, to ensure that the all
        messages are stored in the journal and forwarded to syslog.
        Defaults to
        <literal>notice</literal> for <varname>MaxLevelKMsg=</varname>,
        <literal>info</literal> for <varname>MaxLevelConsole=</varname>,
        and <literal>emerg</literal> for
        <varname>MaxLevelWall=</varname>. These settings may be
        overridden at boot time with the kernel command line options
        <literal>systemd.journald.max_level_store=</literal>,
        <literal>systemd.journald.max_level_syslog=</literal>,
        <literal>systemd.journald.max_level_kmsg=</literal>,
        <literal>systemd.journald.max_level_console=</literal>,
        <literal>systemd.journald.max_level_wall=</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ReadKMsg=</varname></term>

        <listitem><para>Takes a boolean value. If enabled (the
        default), journal reads <filename>/dev/kmsg</filename>
        messages generated by the kernel.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TTYPath=</varname></term>

        <listitem><para>Change the console TTY to use if
        <varname>ForwardToConsole=yes</varname> is used. Defaults to
        <filename>/dev/console</filename>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>LineMax=</varname></term>

        <listitem><para>The maximum line length to permit when converting stream logs into record logs. When a systemd
        unit's standard output/error are connected to the journal via a stream socket, the data read is split into
        individual log records at newline (<literal>\n</literal>, ASCII 10) and NUL characters. If no such delimiter is
        read for the specified number of bytes a hard log record boundary is artificially inserted, breaking up overly
        long lines into multiple log records. Selecting overly large values increases the possible memory usage of the
        Journal daemon for each stream client, as in the worst case the journal daemon needs to buffer the specified
        number of bytes in memory before it can flush a new log record to disk. Also note that permitting overly large
        line maximum line lengths affects compatibility with traditional log protocols as log records might not fit
        anymore into a single <constant>AF_UNIX</constant> or <constant>AF_INET</constant> datagram. Takes a size in
        bytes. If the value is suffixed with K, M, G or T, the specified size is parsed as Kilobytes, Megabytes,
        Gigabytes, or Terabytes (with the base 1024), respectively. Defaults to 48K, which is relatively large but
        still small enough so that log records likely fit into network datagrams along with extra room for
        metadata. Note that values below 79 are not accepted and will be bumped to 79.</para></listitem>
      </varlistentry>

    </variablelist>

  </refsect1>

  <refsect1>
    <title>Forwarding to traditional syslog daemons</title>

    <para>
      Journal events can be transferred to a different logging daemon
      in two different ways. With the first method, messages are
      immediately forwarded to a socket
      (<filename>/run/systemd/journal/syslog</filename>), where the
      traditional syslog daemon can read them. This method is
      controlled by the <varname>ForwardToSyslog=</varname> option. With a
      second method, a syslog daemon behaves like a normal journal
      client, and reads messages from the journal files, similarly to
      <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
      With this, messages do not have to be read immediately,
      which allows a logging daemon which is only started late in boot
      to access all messages since the start of the system. In
      addition, full structured meta-data is available to it. This
      method of course is available only if the messages are stored in
      a journal file at all. So it will not work if
      <varname>Storage=none</varname> is set. It should be noted that
      usually the <emphasis>second</emphasis> method is used by syslog
      daemons, so the <varname>Storage=</varname> option, and not the
      <varname>ForwardToSyslog=</varname> option, is relevant for them.
    </para>
  </refsect1>

  <refsect1>
      <title>See Also</title>
      <para>
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
      </para>
  </refsect1>

</refentry>