在安裝好了MySQL之後，使用了新的配置檔案後，MySQL伺服器可以成功啟動，但在登陸的時候出現了ERROR 2002 (HY000): Can’t connect to local MySQL server through socket，即無法通過socket連線到mysql伺服器，同時提供了socket檔案的位置。下面是這個問題的描述與解決辦法。

1、故障現象
[[email protected] mysqldata]# mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/data/mysqldata/mysql.sock’ (111)

故障環境

[[email protected] mysqldata]# more /etc/issue
CentOS release 5.9 (Final)
Kernel \r on an \m

2、故障分析

檢視mysql例項的狀態

[[email protected] mysqldata]# netstat -ntlp | grep 3306
tcp 0 0 :::3306 :::* LISTEN 13001/mysqld

檢視my.cnf關於socket的配置

[[email protected] mysqldata]# more /etc/my.cnf |grep sock
socket = /tmp/mysql.sock

由上可知my.cnf中定義的為/tmp目錄下，而錯誤提示為/data/mysqldata/目錄下

也就是說mysqld已經聲稱了正確的sock檔案，但客戶端連線還是從初始目錄去找sock檔案

下面檢視後臺日誌，有個ERROR，是關於滿查詢日誌的，是由於目錄不存在而產生的錯誤，與當前故障無關

[[email protected] mysqldata]# 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

3、解決故障
a、通過配置my.cnf mysql選項socket檔案位置解決

先停止mysql伺服器

[[email protected] mysqldata]# service mysqld stop
Shutting down MySQL.[ OK ]

修改my.cnf，如下

[[email protected] mysqldata]# vi /etc/my.cnf
[mysql]
no-auto-rehash
socket = /tmp/mysql.sock #新增該行

重啟mysql伺服器

[[email protected] mysqldata]# service mysqld start
Starting MySQL..[ OK ]

再次連線正常

[[email protected] mysqldata]# mysql -uroot -p
Enter password:
mysql> show variables like ‘version’;
+—————+————+
| Variable_name | Value |
+—————+————+
| version | 5.6.12-log |
+—————+————+

b、為socket檔案建立連結方式
[[email protected] mysqldata]# ln -s /tmp/mysql.sock /data/mysqldata/mysql.sock
ln: creating symbolic link /data/mysqldata/mysql.sock' to/tmp/mysql.sock’: File exists
[[email protected] mysqldata]# rm mysql.sock #上面提示檔案存在，所以刪除之前的mysql.sock檔案
[[email protected] mysqldata]# ln -s /tmp/mysql.sock /data/mysqldata/mysql.sock
[[email protected] mysqldata]# ls -hltr mysql.sock
lrwxrwxrwx 1 root root 15 Oct 11 14:00 mysql.sock -> /tmp/mysql.sock
[[email protected] mysqldata]# mysql -uroot -p
Enter password:
mysql> show variables like ‘socket’;
+—————+—————–+
| Variable_name | Value |
+—————+—————–+
| socket | /tmp/mysql.sock |
+—————+—————–+