How can I redirect process output from a process started with start-stop-daemon on Debian?

linux bash logging debian start-stop-daemon
Pryo picture Pryo · Oct 8, 2012 · Viewed 7.7k times · Source

There are several questions about this already but none of them seem to work. I have a production system that is currently down and I need to be able to get the stderr output from the daemon quickly to debug it.

I thought I could just redirect the output from the point it is called (in an init.d script) but it is proving extremely difficult.

 start-stop-daemon -d $DDIR -b -m --start --quiet -pidfile $PIDFILE --exec $DAEMON -- \
                $DAEMON_ARGS > /var/log/daemon.log 2>&1 \
                || return 2

This does not work. I tried running a shell script that calls the executable and redirects the output but still the log file remained empty (and I do know that the process is outputting information).

Any help would be extremely appreciated.

Answer

Tim S. picture Tim S. · Nov 24, 2016

If you have start-stop-daemon >= version 1.16.5 you simply call it with --no-close to be able to redirect the output of the started process.

From man start-stop-daemon:

-C, --no-close

          Do not close any file descriptor when forcing the daemon into
          the background (since version 1.16.5).  Used for debugging
          purposes to see the process output, or to redirect file
          descriptors to log the process output.  Only relevant when
          using --background.

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