MYSQL之ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock'

登陆时遇到错误：ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2)

解决：

$ /etc/init.d/mysql.server restart
[ ok ] Restarting mysql.server (via systemctl): mysql.server.service.

如果重启还是没有解决，还有一个原因：
由于我们修改了mysql配置“/etc/my.cnf”引起的。比如我们修改了配置文件中“[mysql]”选项下的“socket”参数，而未指定“[client]”、“[mysql]”选项的“socket”参数，导致mysql使用默认的socket文件位置去寻找socket文件，从而导致未找到socket文件而引发此错误。
解决方法：　修改“/etc/my.cnf”配置文件，在配置文件中添加“[client]”选项和“[mysql]”选项，并使用这两个选项下的“socket”参数值，与“[mysqld]”选项下的“socket”参数值，指向的socket文件路径完全一致。如下：

[mysqld]
datadir=/storage/db/mysql
socket=/storage/db/mysql/mysql.sock
...省略n行（爱E族）...
 
[client]
default-character-set=utf8
socket=/storage/db/mysql/mysql.sock
 
[mysql]
default-character-set=utf8
socket=/storage/db/mysql/mysql.sock

具体请参考：http://aiezu.com/article/mysql_cant_connect_through_socket.html

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理论知识：
MYSQL的连接方式有两种：

• 通过本地socket进行连接 【mysql服务器和客户端在同一台机器上】

[mysql]> show variables like 'socket%';  --查看mysql socket文件在哪里
+---------------+-----------------+
| Variable_name | Value           |
+---------------+-----------------+
| socket        | /tmp/mysql.sock |
+---------------+-----------------+

$ mysql -uroot -p123456 -S/tmp/mysql.sock 【本地连接，-S/tmp/mysql.sock可以省略】
[mysql]> \s
--------------
mysql  Ver 8.0.13 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)

Connection id:        20
Current database:    
Current user:        root@localhost
SSL:            Not in use                           -------本地传输，没有网络传输，而ssl是为了防止窃听，因此没有使用ssl
Current pager:        stdout
Using outfile:        ''
Using delimiter:    ;
Server version:        8.0.13 MySQL Community Server - GPL
Protocol version:    10
Connection:        Localhost via UNIX socket   --当前的连接方式是socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:        /tmp/mysql.sock
Uptime:            2 hours 42 min 28 sec

可以在配置文件中$ sudo gedit /etc/my.cnf添加：
[client]
socket=/tmp/mysql.sock

• 通过TCP/IP协议连接【mysql服务器和客户端不在同一台机器上，也可以在一台机器上】

$ mysql -h127.0.0.1 -uroot -p
> show variables like '%ssl%';
+--------------------+-----------------+
| Variable_name      | Value           |
+--------------------+-----------------+
| have_openssl       | YES             |
| have_ssl           | YES             |              ---- 说明已经启用了ssl
 + --------------------------------------+
[mysql]> status
--------------
mysql  Ver 8.0.13 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)

Connection id:        17
Current database:    
Current user:        root@localhost
SSL:            Cipher in use is DHE-RSA-AES128-GCM-SHA256   --启用了ssl
Current pager:        stdout
Using outfile:        ''
Using delimiter:    ;
Server version:        8.0.13 MySQL Community Server - GPL
Protocol version:    10
Connection:        127.0.0.1 via TCP/IP   --当前的连接方式是TCP/IP
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
TCP port:        3306
Uptime:            2 hours 41 min 15 sec

Threads: 2  Questions: 211  Slow queries: 0  Opens: 267  Flush tables: 2  Open tables: 243  Queries per second avg: 0.021
--------------

启动mysql 报错：
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock’ (2)


1.先查看mysql启动状态

#/etc/rc.d/init.d/mysqld status

2.mysql.sock位置查找与验证？

# find / -name mysql.sock
/Data/mydata/mysql.sock
验证目录是否正确
#mysql -u root -p -S /Data/mydata/mysql.sock
备注：-S参数socket file文件验证

3.验证mysql.sock文件权限和用户是否正确？
如果是权限问题，则先改变权限 
#chown -R mysql:mysql /Data/mydata/mysql.sock


[root@localhost ~]# /etc/init.d/mysqld start
启动 MySQL： [ OK]

4.永久解决

修改/etc/my.cnf

添加以下内容到/etc/my.conf:
[client]
socket = /Data/mydata/mysql.sock
[mysqld]
socket = /Data/mydata/mysql.sock