Linux – upstart script not logging to file

This snippet will pipe the output of your service into logger, while still allowing you to exec the service process (thus replacing the shell process) so that upstart doesn't get confused. It also makes sure the logger process is reparented to init, so it's not a child of your service, and it avoids leaving cruft sitting around in the filesystem, even though it needs to create a fifo temporarily.

script
  mkfifo /tmp/myservice-log-fifo
  ( logger -t myservice </tmp/myservice-log-fifo & )
  exec >/tmp/myservice-log-fifo
  rm /tmp/myservice-log-fifo
  exec myservice 2>/dev/null
end script

Here's how it works:

1. mkfifo /tmp/myservice-log-fifo simply makes the fifo special file (aka named pipe). Type man 7 fifo for more info.
2. ( logger ... </tmp/myservice-log-fifo & ) starts logger reading from the fifo, in the background. The parens cause the logger process to be reparented to init, rather than remaining a child of the current shell process.
3. exec >/tmp/myservice-log-fifo redirects the current shell's stdout to the fifo. Now we have an open file descriptor for that fifo, and we don't actually need the filesystem entry any more...
4. rm /tmp/myservice-log-fifo so we'll remove it.
5. exec myservice 2>/dev/null simply runs the service in the usual way. Stdout is already going to the fifo, and that won't change when the new program executes.

UPDATE: set -e is not needed as Upstart runs scripts with this option by default (see http://upstart.ubuntu.com/cookbook/#develop-scripts-using-bin-sh)

sudo by default stomps on most of the environment. Try this (adding -E):

exec sudo -E -u rsyncuser -c "ls -la" >> /tmp/upstart.log 2>&1

-E tells sudo to preserve the environment.