编译mysql后不能初始化innodb

 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!

解决方法：

mv /var/lib/mysql ./mysqlbak

也就是让mysql从新建立这个文件的内容