Error: "mysqld dead but subsys locked"
 

Trying to restart mysqld an got the error message. The interesting part is that killall -9 mysql doesn't kill mysql processes. So the problem still exist.

[root@localhost opt]# /etc/init.d/mysqld status
mysqld dead but subsys locked

First place to look when you get MySQL problems is in the MySQL error file. Have a look in your MySQL directory (could be /var/lib/mysql if you are using MySQL's own RPMs) for a file called foo.err where foo is the name of your host.

Look at the last few entries of this file (you might want to use tail for this) and you may find what's going on.

Have you tried trying to shut down MySQL (irrespective of whether or not you think it is running) before you try to restart?

mysqladmin -p shutdown

This is the only way I feel safe with.

Hope this helps.