MySQL encounters error while restarting: InnoDB: Unable to lock ./ibdata1 error: 11

Symptoms

If MySQL is failing to restart with the following error, it may likely mean that an old MySQL process is running.

[ERROR] InnoDB: Unable to lock ./ibdata1 error: 11
[Note] InnoDB: Check that you do not already have another mysqld process using the same InnoDB data or log files.
[ERROR] InnoDB: Unable to lock ./ibdata1 error: 11
[Note] InnoDB: Check that you do not already have another mysqld process using the same InnoDB data or log files.

Description 

As the error suggests, this error often means that another process for MySQL is currently running. You can check this using the command:# ps faux | grep mysql[d] 

For example:

# ps faux | grep mysql[d]
root      2382 0.0  0.0 113628  1548 ?        S    Apr19  0:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --pid-file=/var/lib/mysql/testing5.cpaneltechs.tld.pid
mysql    2382 0.3  8.0 1790796 327320 ?      Sl  Apr19  4:35  \_ /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/testing5.cpaneltechs.tld.err --pid-file=/var/lib/mysql/testing5.cpaneltechs.tld.pid
mysql    12382 0.1  1.2 652576 49576 ?        Ssl  13:38  0:00 /usr/sbin/mysqld

As shown above, there is an older MySQL process from an older date.

Workaround

The safest way to resolve this is to stop the older MySQL process. This can normally be done using the command:

systemctl stop mysql.service

Then restart MySQL using the command shown here:

/scripts/restartsrv_mysql

Also, these errors can be caused by a failed process from CloudLinux's MySQL Governor. If you are using MySQL Governor, please also ensure that the Governor service is working before starting your MySQL service. You can attempt to restart this process using this command:

systemctl restart db_governor.service