再一次做mysql测试的时候，启动mysql，碰到了
[ERROR] /usr/local/mysql55/bin/mysqld: Can't find file: './mysql/host.frm' (errno: 13)
查看err日志：
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120704 12:58:37 [ERROR] /usr/local/mysql55/bin/mysqld: Can't find file: './mysql/host.frm' (errno: 13)
120704 12:58:37 [ERROR] Fatal error: Can't open and lock privilege tables: Can't find file: './mysql/host.frm' (errno: 13)
120704 12:59:33 [Note] Plugin 'FEDERATED' is disabled.
/usr/local/mysql55/bin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
120704 12:59:33 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
120704 12:59:33 InnoDB: Error: trying to open a table, but could not
InnoDB: open the tablespace file './zsd/t1.ibd'!
120704 12:59:34 [ERROR] /usr/local/mysql55/bin/mysqld: Can't find file: './mysql/host.frm' (errno: 13)
120704 12:59:34 [ERROR] Fatal error: Can't open and lock privilege tables: Can't find file: './mysql/host.frm' (errno: 13)
120704 12:59:34 mysqld_safe mysqld from pid file /data/mysqldata/3306/mysql.pid ended
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红字明确了最重要的片段。当然，120704代表的是当天日期，要分析的时候，可以grep当天日期，查看err日志。
由于我之前做了数据目录的cp
只要对数据的权限做一些更改
[root@localhost 3306]# chown mysql:mysql ./*
重新启动mysql服务，即可
