InnoDB registration as a STORAGE ENGINE failed

nano /var/lib/mysql/

141212 17:26:27 [ERROR] Plugin 'InnoDB' init function returned error.
141212 17:26:27 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed 

There are two solutions to this particular problem:

1. Restore the my.cnf file to its original state, with an innodb_log_file_size equal to the actual size of the existing InnoDB log files.

2. Rename or move both the ./ib_logfile0 and ./ib_logfile1 files, and then start the MySQL server.
The ./ib_logfile0 and ./ib_logfile1 files are located in the InnoDB data directory (usually /var/lib/mysql). Both files must be moved or renamed for the above procedure to work. When starting MySQL, new InnoDB log files of the appropriate size will be created.

The original InnoDB log files only need to be kept as long as they may be needed for data recovery. If the MySQL server successfully starts after the above procedure, and all data is intact, the original InnoDB log files can be discarded.