Debian uses a script and a program start-stop-daemon.  FRom the man page:

       Note: unless --pidfile is specified, start-stop-daemon behaves  similar  to  killall(1).   start-stop-daemon  will  scan  the
       process  table  looking  for any processes which match the process name, uid, and/or gid (if specified). Any matching process
       will prevent --start from starting the daemon. All matching processes will be sent the TERM signal (or the one specified  via
       --signal  or --retry) if --stop is specified. For daemons which have long-lived children which need to live through a --stop,
       you must specify a pidfile.

Of course, one can get the pid by doing

 guix-daemon --blah-blah & 
 pid=$!

But the problem here is that the & means you never know when the daemon has actually started,
which leads to race conditions.  Again, there are tricks to work around that, but having the daemon 
write its own pid makes it a lot easier.

J'

On Sun, Dec 08, 2013 at 04:35:40PM +0100, Ludovic Courtès wrote:
     John Darrington <john@darrington.wattle.id.au> skribis:
     
     > I don't know what you will think of this patch.  But I found that it makes 
     > running guix under debian a whole lot easier.  I suspect the same will be
     > true for many other OSes too.
     
     How does it help exactly?  On GNU, it’s started by dmd, which knows its PID.
     I’d expect it to be the same with other init systems, no?
     
     Thanks,
     Ludo’.

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