“Another MySQL daemon already running with the same unix socket” – error while starting MYSQL

In our environment we had run cluster fencing tests, after hard-reboot our MySQL will not start.

# service mysqld status
mysqld is stopped

# service mysqld start
Another MySQL daemon already running with the same unix socket.
Starting mysqld:                                           [FAILED]

The Solution

The root cause of the above error is that MySQL was not closed properly, during database shutdown. Due to this socket file is not removed by MySQL and had to be removed manually.

1. Verify that MySQL is not running on your system:

# ps aux | grep -i sql
root     10154  0.0  0.0 103252   840 pts/0    S+   11:21   0:00 grep -i sql

2. Remove leftover socket file using following command:

# rm -Rf /var/lib/mysql/mysql.sock

3. Start the MySQL database and verify if its running properly.

# service mysqld start

# service mysqld status