MySQL Error : Unable to lock ./ibdata1 error: 11

Error :

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

File :  /var/log/mysql/error.log

Fix :

1. 1. lsof -i:3306
   2.  
   3. ////Get PID
   4.  
   5. ////example :
   6. COMMAND  PID  USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
   7. mysqld  2644 mysql   51u  IPv4  20139      0t0  TCP localhost:mysql (LISTEN)
   8.  
   9. kill -9 PROCESS (PID)
   10.  
   11. sudo service mysql restart