man: describe various logging configuration variables

Fixes #17484.

This patch affects systemctl(1), as well as all man pages that include
all of common-variables.xml, i.e. most of our command line tools.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2021-02-28 13:22:06 +01:00
parent 4ef3ca3447
commit 5bd27a17ca
2 changed files with 78 additions and 0 deletions

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@ -7,6 +7,79 @@
<title>Environment</title>
<variablelist class='environment-variables'>
<varlistentry id='log-level'>
<term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
<listitem><para>The maximum log level of emitted messages (messages with a higher log level, i.e. less
important ones, will be suppressed). Either one of (in order of decreasing importance)
<constant>emerg</constant>, <constant>alert</constant>, <constant>crit</constant>,
<constant>err</constant>, <constant>warning</constant>, <constant>notice</constant>,
<constant>info</constant>, <constant>debug</constant>, or an integer in the range 0…7. See
<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more information.</para>
</listitem>
</varlistentry>
<varlistentry id='log-color'>
<term><varname>$SYSTEMD_LOG_COLOR</varname></term>
<listitem><para>A boolean. If true, messages written to the tty will be colored according to
priority.</para>
<para>This setting is only useful when messages are written directly to the terminal, because
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and
other tools that display logs will color messages based on the log level on their own.</para>
</listitem>
</varlistentry>
<varlistentry id='log-time'>
<term><varname>$SYSTEMD_LOG_TIME</varname></term>
<listitem><para>A boolean. If true, log messages will be prefixed with a timestamp.</para>
<para>This setting is only useful when messages are written directly to the terminal or a file, because
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> and
other tools that display logs will attach timestamps based on the entry metadata on their own.</para>
</listitem>
</varlistentry>
<varlistentry id='log-location'>
<term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
<listitem><para>A boolean. If true, messages will be prefixed with a filename and line number
in the source code where the message originates.</para>
<para>Note that the log location is often attached as metadata to journal entries anyway. Including it
directly in the message text can nevertheless be convenient when debugging programs.</para>
</listitem>
</varlistentry>
<varlistentry id='log-tid'>
<term><varname>$SYSTEMD_LOG_TID</varname></term>
<listitem><para>A boolean. If true, messages will be prefixed with the current numerical thread ID
(TID).</para>
<para>Note that the this information is attached as metadata to journal entries anyway. Including it
directly in the message text can nevertheless be convenient when debugging programs.</para>
</listitem>
</varlistentry>
<varlistentry id='log-target'>
<term><varname>$SYSTEMD_LOG_TARGET</varname></term>
<listitem><para>The destination for log messages. One of <constant>console</constant> (log to the
attached tty), <constant>console-prefixed</constant> (log to the attached tty but with prefixes
encoding the log level and "facility", see <citerefentry
project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<constant>kmsg</constant> (log to the kernel circular log buffer), <constant>journal</constant> (log to
the journal), <constant>journal-or-kmsg</constant> (log to the journal if available, and to kmsg
otherwise), <constant>auto</constant> (dermine the appropriate log target automatically, the default),
<constant>null</constant> (disable log output).</para>
<!-- <constant>syslog</constant>, <constant>syslog-or-kmsg</constant> are deprecated -->
</listitem>
</varlistentry>
<varlistentry id='pager'>
<term><varname>$SYSTEMD_PAGER</varname></term>

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@ -2407,6 +2407,11 @@ Jan 12 10:46:45 example.com bluetoothd[8900]: gatt-time-server: Input/output err
</para></listitem>
</varlistentry>
</variablelist>
<xi:include href="common-variables.xml" xpointer="log-level"/>
<xi:include href="common-variables.xml" xpointer="log-color"/>
<xi:include href="common-variables.xml" xpointer="log-time"/>
<xi:include href="common-variables.xml" xpointer="log-location"/>
<xi:include href="common-variables.xml" xpointer="log-target"/>
<xi:include href="common-variables.xml" xpointer="pager"/>
<xi:include href="common-variables.xml" xpointer="less"/>
<xi:include href="common-variables.xml" xpointer="lesscharset"/>