qmail supervise - unable to acquire errors

supervise: fatal: unable to acquire qmail-smtpd/supervise/lock:
temporary failure

There are lots of posts in qmail groups about supervise errors that
occur during a qmail stop | start. I couldn't find any posts that were
of particular use, so I'm posting this.

qmailctl references executables without absolute paths (obviously) so
if your path environment variable cannot accomdate qmailctl, 'qmailctl
stop' will not shutdown qmail correctly.

If you then do 'qmailctl start' you will be starting new qmail
processes where old ones have not been shut down. This is what causes
the 'unable to acquire' error messages in relation to the various
daemons that are run under svcscan.

Firstly, to get rid of the annoying screen output, kill svcscan:

cat /var/run/svscan.pid # find the PID
then use kill to get rid of it

Then, find out what qmail processes are still running:

ps -axww | grep qmail | grep -v multilog | grep -v supervise

(supervise and multilog process aren't a problem)

Kill whatever processes you can at this point, so that you're left with
whatever zombie process (the ones in square brackets) that have been
created because of the ineffectual stop|start.

Finally, delete the lock files references in the error messages eg

rm -f /var/qmail/supervise/qmail-smtpd/supervise/lock

touch them to re-create them eg

touch /var/qmail/supervise/qmail-smtpd/supervise/lock

(This breaks the lock between the zombie process and the file)

and then do a 'qmailctl restart'

This works for me. I'm not sure if my logic is entirely correct, but it
saves doing a reboot.