[Mailman-Users] Mailman refusing to stop/start with errors PID unreadable

[Andrew Steele]

We are currently in the process of moving our mailing lists to a new 
virtual server.  The new server is using Webmin/Virtualmin 'control 
panel'.

When installed, Mailman appears in the control panel and we can set up 
our lists without a problem.

However, we have, twice had Mailman suddenly stop working.

If we issue a shell command to mailmanctl to STOP using 
/var/lib/mailman/bin/mailmanctl stop we get the following warning that 
the PID in unreadable.

     Shutting down Mailman's master qrunner
     PID unreadable in: /var/run/mailman/mailman.pid
     [Errno 2] No such file or directory: '/var/run/mailman/mailman.pid'
     Is qrunner even running?

Attempting to restart the qrunner using: 

     /var/lib/mailman/bin/mailmanctl -s start

Produces a series of warning messages and the qrunner does not restart. 

     Traceback (most recent call last):
       File "/var/lib/mailman/bin/mailmanctl", line 554, in ?
         main()
       File "/var/lib/mailman/bin/mailmanctl", line 389, in main
         lock = acquire_lock(force)
       File "/var/lib/mailman/bin/mailmanctl", line 213, in acquire_lock
         lock = acquire_lock_1(force)
       File "/var/lib/mailman/bin/mailmanctl", line 198, in 
     acquire_lock_1
         lock.lock(0.1)
       File "/var/lib/mailman/Mailman/LockFile.py", line 243, in lock
         self.__write()
       File "/var/lib/mailman/Mailman/LockFile.py", line 422, in __write
         fp = open(self.__tmpfname, 'w')
     IOError: [Errno 2] No such file or directory: 
     '/var/lib/mailman/locks/master-qrunner.airedale.9290.1'

Our only solution, so far, has been to remove and reinstall Mailman.  
This is OK whilst we are setting everything up but will not be adequate 
once we 'go live'.

Can anyone offer a solution?  It isn't clear what is triggering this 
occurrence... :-(

Any insight and advice gratefully received.

Andrew