Recently I upgraded the MySQL server and I enabled InnoDB and then I was not able to start the MySQL Server.
The next step was to check the mysql logs and I saw the error:
InnoDB: Error: log file ./ib_logfile0 is of different size 0 5256780 bytes
InnoDB: than specified in the .cnf file 0 1077645824 bytes!
[ERROR] Plugin ‘InnoDB’ init function returned error.
[ERROR] Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.
[ERROR] Unknown/unsupported storage engine: InnoDB
The solution for this error is:
Remove the ib_logfile0 and ib_logfile1 files located in /var/lib/mysql.
Then just start the Mysql Server and should be fine now.