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。