WebLogic server Error: Could not obtain an exclusive lock for directory.

Steps to get out of this situation:

1. Shutdown the server.
2. Delete the lok file from <domain-home>/servers/<server-name>/tmp/.
3. Try to start the server.
4. If the server still fails to start then find the process which is still running on this server using following commands.

ps -ef | grep 'weblogic'

OR
ps -ef | grep 'oracle'

kill -9 PID

4. Now start the server.