排查修復數據表的經過：

1、訪問網頁，提示錯誤，連接不到數據庫。

2、啟動mysql服務，卸載和關閉rpm安裝的mysql服務

（昨天安裝postfix好像yum安裝了mysql），用netstat -anp |grep mysqld 命令查看mysql服務沒有起來，用mysql -uroot -p也連接不到服務器。

3、查看錯誤提示：

110726 17:02:23 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. 
110726 17:02:23 [ERROR] /usr/local/mysql/libexec/mysqld: Table './mysql/host' is marked as crashed and last (automatic?) repair failed 
110726 17:02:23 [ERROR] Fatal error: Can't open and lock privilege tables: Table './mysql/host' is marked as crashed and last (automatic?) repair failed 110726 17:02:23 mysqld_safe mysqld from pid file /var/lib/mysql/localhost.localdomain.pid ended 
110726 17:24:31 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql 
110726 17:24:31 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
發現提示數據庫表損壞。（./mysql/host）

4、修復數據庫表：

cd /var/lib/mysql/mysql 
myisamchk -of host.MYI 
- recovering (with keycache) MyISAM-table 'host.MYI' 
Data records: 0 
表host.MYI修復成功。

5、再次啟動服務，查看服務是否啟動，登錄mysql，還是不行。所以再次查看錯誤日志。

/usr/local/mysql/libexec/mysqld: Table './mysql/plugin' is marked as crashed and last (automatic?) repair failed 
/usr/local/mysql/libexec/mysqld: Table 'plugin' is marked as crashed and last (automatic?) repair failed 
110726 17:24:31 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. 
110726 17:24:31 [ERROR] /usr/local/mysql/libexec/mysqld: Table './mysql/user' is marked as crashed and last (automatic?) repair failed 
110726 17:24:31 [ERROR] Fatal error: Can't open and lock privilege tables: Table './mysql/user' is marked as crashed and last (automatic?) repair failed 110726 17:24:31 mysqld_safe mysqld from pid file /var/lib/mysql/localhost.localdomain.pid ended 
110726 17:27:13 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql 
110726 17:27:13 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.

6、又發現./mysql/user表損壞。

[root@localhost mysql]# myisamchk -of user.MYI 
- recovering (with keycache) MyISAM-table 'user.MYI' 
Data records: 6

7、表修復成功，但是還是啟動不了服務，繼續看錯誤日志。

/usr/local/mysql/libexec/mysqld: Table './mysql/plugin' is marked as crashed and last (automatic?) repair failed 
/usr/local/mysql/libexec/mysqld: Table 'plugin' is marked as crashed and last (automatic?) repair failed 
110726 17:27:13 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.