Mysql 启动失败： Can not open the mysql.plugin table

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最近将伺服器搬家，於是将原机器所装的软体改装到新机器，并且 OS 从 CentOS 5.8 升到 CentOS 6.5，结果其中一个软体 Mysql 一直有问题。

Mysql Error

140216 13:56:04 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
 
140216 13:56:05 mysqld_safe Starting mysqld daemon with databases from /www/data/mysqldata/
 
/usr/mysql/libexec/mysqld: Table 'mysql.plugin' doesn't exist
 
140216 13:56:05 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
 
140216 13:56:05 [ERROR] Can't open and lock privilege tables: Table 'mysql.servers' doesn't exist
 
140216 13:56:05 [ERROR] Column count of mysql.db is wrong. Expected 22, found 20. Created with MySQL 50024, now running 50170. Please use mysql_upgrade to fix this error.

首先我使用 mysql_upgrade 更新资料库看看，结果如下：

mysql_upgrade

Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
 
Running 'mysqlcheck with default connection arguments
 
mysqlcheck: Got error: 2002: Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2) when trying to connect
FATAL ERROR: Upgrade failed

在这里有看到一个 error 2002 ，去 Mysql 官网查询后，发现是 Permission Deny ，一开始想说可能是我的资料库 owner 并不是「mysql」这个帐号，但是我启动 mysql 时，有指定 --user=mysql，接著我使用指令

sudo chown -R mysql:mysql /mysqldata

将资料库档案的 owner , group 全部改掉，都改成 Mysql。

但是改完之后，问题仍然存在，后来追查下发现 /etc/my.cnf 这个 Mysql config 的设定没有更新到，於是我更新这个档案，加入如下的设定后， Mysql 就能正常的启动罗

my.cnf

[mysqld] 
datadir=/mysqldata 
socket=/tmp/mysql.sock 
[client] 
socket=/tmp/mysql.sock

问题 2 : mariadb.pid

Mysql 不知为何，突然说无法建立这个档案 /var/run/mariadb/mariadb.pid

log file: /var/log/mariadb/mariadb.log

160226 16:10:27 mysqld_safe Starting mysqld daemon with databases from /var/MysqlData/
160226 16:10:27 [ERROR] /usr/local/share/mysql/libexec/mysqld: Can't create/write to file '/var/run/mariadb/mariadb.pid' (Errcode: 13)
160226 16:10:27 [ERROR] Can't start server: can't create PID file: Permission denied
160226 16:10:27 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended

解决方式为建立 /var/log/mariadb/, /var/run/mariadb/ 资料夹，并将这个资料夹的权限改成 777 或是 owner 改成 mysql 。

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This post was last modified by puritys 2016/06/28