ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
背景：
mysql -uroot -p123456
提示：
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
原因：
mysql.sock文件是服务器与本地客户端进行通信的Unix套接字文件，默认位置是/tmp/MySQL.sock。可能此文件不存在。
解决：
四种方案
- 在使用mysql 连接的本地数据库时， 命令行添加参数指定，sock 文件的地址
- 配置my.cnf 的 [client] 指定 sock 文件的地址
- 修改MYSQL_UNIX_PORT环境变量， 将其设置为 unix sock 文件的路径
- 重新编译指定 --with-unix-socket-path 选项
方法一
查看当前机器已启动的mysqld使用的socket文件的位置如下：
[user_00@localhost ~]$ ps -ef | grep mysqld
root 5905 1 0 21:08 pts/17 00:00:00 /bin/sh /usr/local/services/mysql-5.6.24/bin/mysqld_safe --datadir=/data/mysql --pid-file=/data/mysql/mysqld.pid
mysql 6144 5905 0 21:08 pts/17 00:00:02 /usr/local/services/mysql-5.6.24/bin/mysqld --basedir=/usr/local/services/mysql-5.6.24 --datadir=/data/mysql --plugin-dir=/usr/local/services/mysql-5.6.24/lib/plugin --user=mysql --log-error=/data/mysql/mysql.err --pid-file=/data/mysql/mysqld.pid --socket=/data/mysql/mysql.sock --port=3306
user_00 6430 5575 0 21:14 pts/19 00:00:00 grep --color=auto mysqld
当前机器监听的本地socket 文件是：
--socket=/data/mysql/mysql.sock
或者，可以通过如下查询：
[user_00@localhost ~]$ netstat -xl | grep mysql
unix 2 [ ACC ] STREAM LISTENING 115130474 /data/mysql/mysql.sock
故可以使用如下方式进行连接：
[user_00@localhost ~]$ mysql -uroot -p123456 -S /data/mysql/mysql.sock
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.6.24 Source distribution
Copyright (c) 2000, 2015, 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>
方法二
在mysql的配置文件 /etc/my.cnf 中指定链接的socket 的地址
[client]
socket=/data/mysql/mysql.sock
再连接，成功
[user_00@localhost ~]$ mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 2
Server version: 5.6.24 Source distribution
Copyright (c) 2000, 2015, 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>
方法三
将MYSQL_UNIX_PORT环境变量设置为Unix套接字文件的路径
[user_00@localhost ~]$ echo $MYSQL_UNIX_PORT
[user_00@localhost ~]$ export MYSQL_UNIX_PORT=/data/mysql/mysql.sock
[user_00@localhost ~]$ mysql -uroot -p123456
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 3
Server version: 5.6.24 Source distribution
Copyright (c) 2000, 2015, 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>
方法四
源码编译MySQL，不用默认Unix套接字文件位置。使用 --with-unix-socket-path 选项指定路径。
检查
用 mysqladmin 连接服务器，测试套接字位置是否正确
[user_00@localhost ~]$ mysqladmin -uroot -p123456 --socket=/data/mysql/mysql.sock version
mysqladmin Ver 9.0 Distrib 5.5.41-MariaDB, for Linux on x86_64
Copyright (c) 2000, 2014, Oracle, MariaDB Corporation Ab and others.
Server version 5.6.24
Protocol version 10
Connection Localhost via UNIX socket
UNIX socket /data/mysql/mysql.sock
Uptime: 29 min 35 sec
Threads: 1 Questions: 6 Slow queries: 0 Opens: 70 Flush tables: 1 Open tables: 63 Queries per second avg: 0.003
用错误的 socket 文件，提示如下
[user_00@localhost ~]$ mysqladmin -uroot -p123456 --socket=/data/mysql/mysqle.sock version
mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/data/mysql/mysqle.sock' (2)'
Check that mysqld is running and that the socket: '/data/mysql/mysqle.sock' exists!