mysql无法起动怎么回事 错误信息看不懂 帮我看下啊

050628 13:03:41 mysqld started
050628 13:03:42 InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'create'.
InnoDB: Cannot continue operation.
050628 13:03:42 mysqld ended