First look at the ib_logfile0 and ib_logfile1 in /var/lib/mysql.

If they have been set to size different from the default, that probably will prevent mysqld’s startup. The default for innodb_lkog_file_size is 5M.

Add this in my.cnf

[mysqld]
innodb_log_file_size = 12M

And then Proceed by doing following

/etc/init.d/mysql stop

mv /var/lib/mysql/ib_logfile0 /var/lib/mysql/ib_logfile0.bak # these are your
mv /var/lib/mysql/ib_logfile1 /var/lib/mysql/ib_logfile1.bak # log files

/etc/init.d/mysql start