If you’re getting the following error starting Postfix on a Virtualmin system:
Postfix Failed to start : unable to set exclusive lock: Resource temporarily unavailable
You need to kill the process and start Postfix using the proper command.
To find the process:
#fuser /var/lib/postfix/master.lock
7881
Then kill it:
#kill 7881
Note:
If your system cannot find fuser
following this article.