Php Nagios/MySQL错误

我从Nagios收到一个停机警报，说mysql在主机上停机。我登录到主机，在mysql error.log文件中发现以下错误。解决此问题的正确步骤是什么

root@ubuntu:/var/log# tail -f mysql/error.log
101202 11:09:21 [ERROR] Can't open the mysql.plugin table. Please run 
                        mysql_upgrade to create it.
101202 11:09:21  InnoDB: Started; log sequence number 0 44233
101202 11:09:21 [ERROR] /usr/sbin/mysqld: Can't find file: './mysql/host.frm' 
                        (errno: 13)
101202 11:09:21 [ERROR] Fatal error: Can't open and lock privilege tables: 
                        Can't find file: './mysql/host.frm' (errno: 13)
101202 11:09:51 [Note] Plugin 'FEDERATED' is disabled.
                       /usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' 
                       (errno: 13)
101202 11:09:51 [ERROR] Can't open the mysql.plugin table. Please run 
                        mysql_upgrade to create it.
101202 11:09:52  InnoDB: Started; log sequence number 0 44233
101202 11:09:52 [ERROR] /usr/sbin/mysqld: Can't find file: './mysql/host.frm' 
                        (errno: 13)
101202 11:09:52 [ERROR] Fatal error: Can't open and lock privilege tables: 
                        Can't find file: './mysql/host.frm' (errno: 13)
101202 11:10:22 [Note] Plugin 'FEDERATED' is disabled.
                       /usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' 
                       (errno: 13)
101202 11:10:22 [ERROR] Can't open the mysql.plugin table. Please run 
                        mysql_upgrade to create it.
101202 11:10:22  InnoDB: Started; log sequence number 0 44233
101202 11:10:22 [ERROR] /usr/sbin/mysqld: Can't find file: './mysql/host.frm' 
                        (errno: 13)
101202 11:10:22 [ERROR] Fatal error: Can't open and lock privilege tables: 
                        Can't find file: './mysql/host.frm' (errno: 13)

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找出MySQL找不到表的原因。转到MySQL数据目录并查找MySQL子目录（对应于

MySQL

数据库，其中包含用户、进程、权限等内容）。也许有人删除了mysql数据库。可能有人重写了您的my.cnf配置文件，其中一个指向错误的数据目录。

您检查了文件路径吗？