Mysql 启动时 报ERROR 2002，分析解决、

1、故障现象

[root@localhost scripts]# mysql -u root
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysqld.sock' (2)

2、故障分析

查看mysql实例的状态

[root@localhost scripts]# netstat -ntlp  | grep 3306
tcp        0      0 :::3306                    :::*                        LISTEN      13001/mysqld

查看my.cnf关于socket的配置

[root@localhost scripts]# more /etc/my.cnf |grep sock
socket = /tmp/mysqld.sock

也就是说mysqld已经声称了正确的sock文件，但客户端连接还是从初始目录去找sock文件

下面查看后台日志，有个ERROR，是关于满查询日志的，是由于目录不存在而产生的错误，与当前故障无关

[root@localhost scripts]# more SZDB.err
            ............
2014-10-11 13:17:21 13001 [Note] InnoDB: 5.6.12 started; log sequence number 1625997
/app/soft/mysql/bin/mysqld: File '/log/mysql_logs/slowquery.log' not found (Errcode: 2 - No such file or directory)
2014-10-11 13:17:21 13001 [ERROR] Could not use /log/mysql_logs/slowquery.log for logging (error 2). Turning logging off for the who
le duration of the MySQL server process. To turn it on again: fix the cause, shutdown the MySQL server and restart it.
2014-10-11 13:17:21 13001 [Note] Server hostname (bind-address): '*'; port: 3306
2014-10-11 13:17:21 13001 [Note] IPv6 is available.
2014-10-11 13:17:21 13001 [Note]  - '::' resolves to '::';
2014-10-11 13:17:21 13001 [Note] Server socket created on IP: '::'.
2014-10-11 13:17:21 13001 [Note] Event Scheduler: Loaded 0 events
2014-10-11 13:17:21 13001 [Note] /app/soft/mysql/bin/mysqld: ready for connections.
Version: '5.6.12-log'  socket: '/tmp/mysql.sock'  port: 3306  Source distribution
#Author ：Leshami
#Blog  : http://www.linuxidc.com

3、解决故障

a、通过配置my.cnf mysql选项socket文件位置解决

先停止mysql服务器

[root@localhost scripts]# systemvtl restart mysqld
Shutting down MySQL.[  OK  ]

修改my.cnf，如下

[root@localhost scripts]# vi /etc/my.cnf
[mysql]
no-auto-rehash
socket = /tmp/mysqld.sock  #添加该行

重启mysql服务器

[root@localhost scripts]# systemctl restart mysqld 
Starting MySQL..[  OK  ]

再次连接正常

[root@localhost scripts]# mysql -uroot -p
Enter password:
mysql> show variables like 'version';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| version      | 5.6.12-log |
+---------------+------------+

b、为socket文件建立链接方式

[root@SZDB mysqldata]# ln -s /tmp/mysql.sock /data/mysqldata/mysql.sock
ln: creating symbolic link `/data/mysqldata/mysql.sock' to `/tmp/mysql.sock': File exists
[root@SZDB mysqldata]# rm mysql.sock    #上面提示文件存在，所以删除之前的mysql.sock文件
[root@SZDB mysqldata]# ln -s /tmp/mysql.sock /data/mysqldata/mysql.sock
[root@SZDB mysqldata]# ls -hltr mysql.sock
lrwxrwxrwx 1 root root 15 Oct 11 14:00 mysql.sock -> /tmp/mysql.sock
[root@SZDB mysqldata]# mysql -uroot -p
Enter password:
mysql> show variables like 'socket';
+---------------+-----------------+
| Variable_name | Value          |
+---------------+-----------------+
| socket        | /tmp/mysql.sock |
+---------------+-----------------+