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.
110726 17:27:13 [ERROR] /usr/local/mysql/libexec/mysqld: Table './mysql/db' is marked as crashed and last (automatic?) repair failed
110726 17:27:13 [ERROR] Fatal error: Can't open and lock privilege tables: Table './mysql/db' is marked as crashed and last (automatic?) repair failed
110726 17:27:13 mysqld_safe mysqld from pid file /var/lib/mysql/localhost.localdomain.pid ended
8、最后一個錯誤，是./mysql/db表還沒有修復好繼續修復./mysql/db表。
9、執行下面的命令修復./mysql/db表：
[root@localhost mysql]# myisamchk -of db.MYI
- recovering (with keycache) MyISAM-table 'db.MYI'
Data records: 0
Data records: 2
10、最后啟動mysql服務。
/usr/local/mysql/bin/mysqld_safe &
11、查看服務是否在運行。
[root@localhost ~]# netstat -anp | grep mysqld
tcp0 0
0.0.0.0:3306
0.0.0.0:* LISTEN
4360/mysqld
unix 2 [ ACC ] STREAM LISTENING 14172
4360/mysqld /tmp/mysql.sock
這時發現服務已運行。
12、登錄mysql試試。
[root@localhost ~]# mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 35
Server version: 5.1.55-log Source distribution
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL v2 license
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
可以登錄。
13、打開網頁，已經可以正常訪問了，說明MySQL數據庫的數據表修復成功。
