can't redirect (debug) output of systemd-udevd

[mbiebl]

I'm trying to run systemd-udevd in debug and redirecting the output to a file.
Reading the man page about --debug I tried the following:

/lib/systemd/systemd-udevd --debug 2> /tmp/udev.log

But that file just remains empty. Am I doing something wrong or is this a bug?

[kaysievers]

The log should just end up in the journal because the redirect is not a tty anymore.
You should be able to add SYSTEMD_LOG_TARGET=console.

[kaysievers]

Added log_set_target(LOG_TARGET_CONSOLE); to the code.

We should probably just remove the --debug option and document in the man page how to use the environment variables. No other systemd tool has this switch.

[mbiebl]

In this particular case I was running udev under sysvinit, so no journal is available.

[dvdhrm]

For more details, see src/basic/log.c. The STDERR ("console") fallback is really the last option we chose by default. So if the journal is not available, we still try kmsg.

By setting SYSTEMD_LOG_TARGET appropriately, you can avoid this behavior, as Kay explained.

[mbiebl]

2015-07-01 23:14 GMT+02:00 David Herrmann notifications@github.com:

For more details, see src/basic/log.c. The STDERR ("console") fallback is
really the last option we chose by default. So if the journal is not
available, we still try kmsg.

By setting SYSTEMD_LOG_TARGET appropriately, you can avoid this behavior,
as Kay explained.

Is this behaviour of systemd-udevd documentend somewhere?

Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

[dvdhrm]

Hm, they environment variables are global for all systemd utilities. The only real reference I see is systemd(1).

[keszybz]

systemd-active(1) has

    <title>Environment variables</title>
    <variablelist class='environment-variables'>
      <varlistentry>
        <term><varname>$LISTEN_FDS</varname></term>
        <term><varname>$LISTEN_PID</varname></term>

        <listitem><para>See
        <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$SYSTEMD_LOG_TARGET</varname></term>
        <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
        <term><varname>$SYSTEMD_LOG_COLOR</varname></term>
        <term><varname>$SYSTEMD_LOG_LOCATION</varname></term>

        <listitem><para>Same as in
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para></listitem>
      </varlistentry>
    </variablelist>

Second half of this paragraph could be added to other man pages, probably as a xi:include.