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就在刚刚，MySQL 服务器意外掉电关机 - 设备启动后，无硬件报错，无法启动多实例
[root@db02 ~]# mysql -uroot -S /data/3306/mysql.sock
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/data/3306/mysql.sock’ (111)
## 无法连接到本地 mysql socket ##
查看日志：没有记录 error
尝试启动 mysql 服务，失败
[root@db02 ~]# /data/3306/mysql start
MySQL is running…
[root@db02 ~]# ps -ef|grep msyql #但 mysql 进程并没有启动
root 1327 1273 0 13:25 pts/0 00:00:00 grep –color=auto msyql
[root@db02 ~]#
然后想起 mysql 启动原理，就是通过 mysql 启动脚本，然后调用 mysqld_safe 脚本，最后调用 mysqld 主进程，启动 mysql 服务，生成 socket 文件，所以我去根目录查看，发现服务没有启动 但有个 socket 文件
修复 mysql
[root@db02 3306]# ls /data/3306/data mysql mysql-bin.000002 mysql-bin.index mysql_oldboy3306.errmy.cnf mysql-bin.000001 mysql-bin.000003 mysqld.pid mysql.sock
## 怀疑是刚才意外关机，msyql 服务卡死，造成 sock 文件没有移除，所以考虑将 sock 改名或移动到 /tmp
[root@db02 3306]# cp /data/3306/mysql.sock{,.bak} #将 sock 文件移除
开启 MySQL 服务
[root@db02 3306]# /data/3306/mysql start #开启 mysql 服务
Starting MySQL…
[root@db02 3306]# ps -ef|grep mysql #启动正常
root 1363 1 0 13:31 pts/0 00:00:00 /bin/sh /application/mysql/bin/mysqld_safe –defaults-file=/data/3306/my.cnf
mysql 2087 1363 3 13:31 pts/0 00:00:00 /application/mysql-5.5.32/bin/mysqld –defaults-file=/data/3306/my.cnf –basedir=/application/mysql –datadir=/data/3306/data –plugin-dir=/application/mysql/lib/plugin –user=mysql –log-error=/data/3306/mysql_oldboy3306.err –open-files-limit=1024 –pid-file=/data/3306/mysqld.pid –socket=/data/3306/mysql.sock –port=3306
root 2106 1273 0 13:31 pts/0 00:00:00 grep –color=auto mysql
开启 MySQL 多实例
[root@db02 3306]# mysql -uroot -p -S /data/3306/mysql.sock
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.5.32-log Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.
mysql>
到此为止，恢复正常。
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