yum remove mysql-* -y
yum install php-mysql MariaDB-server -y
service mysql start
出现错误：
Starting MySQL. ERROR! The server quit without updating PID file (/var/lib/mysql/AY130906195906317111Z.pid).
查看日志：
131208 19:51:37 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
131208 19:51:37 [Note] InnoDB: The InnoDB memory heap is disabled
131208 19:51:37 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
131208 19:51:37 [Note] InnoDB: Compressed tables use zlib 1.2.3
131208 19:51:37 [Note] InnoDB: CPU does not support crc32 instructions
131208 19:51:37 [Note] InnoDB: Using Linux native AIO
131208 19:51:37 [Note] InnoDB: Initializing buffer pool, size = 128.0M
131208 19:51:37 [Note] InnoDB: Completed initialization of buffer pool
131208 19:51:37 [ERROR] InnoDB: auto-extending data file ./ibdata1 is of a different size 640 pages (rounded down to MB) than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages!
131208 19:51:37 [ERROR] InnoDB: Could not open or create the system tablespace. If you tried to add new data files to the system tablespace, and it failed here, you should now edit innodb_data_file_path in my.cnf back to what it was, and remove the new ibdata files InnoDB created in this failed attempt. InnoDB only wrote those files full of zeros, but did not yet use them in any way. But be careful: do not remove old data files which contain your precious data!
131208 19:51:37 [ERROR] Plugin 'InnoDB' init function returned error.
131208 19:51:37 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
131208 19:51:37 [Note] Plugin 'FEEDBACK' is disabled.
131208 19:51:37 [ERROR] Unknown/unsupported storage engine: InnoDB
131208 19:51:37 [ERROR] Aborting
131208 19:51:37 [Note] /usr/sbin/mysqld: Shutdown complete
服务可能没杀干净，有pid号重叠，将pid文件备份删除看看，它会自动生成。