This just happened to me: mysql went down for no apparent reason and I thought it was because I was missing with the .ini file. No matter how I tried, it wouldn't restart.
I checked the error logs and found:
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
This was an indicator that a mysql process was already running it, but I couldn't find it on top, or using
ps aux | grep mysql
So I tried this:
# lsof -i:3306
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
mysqld 24416 mysql 10u IPv4 173905 0t0 TCP localhost:mysql (LISTEN)
# sudo kill 24416
# sudo /etc/init.d/mysql start
That's all it took.
In this case.