<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>