Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

很明显，找不到/var/lib/mysql/mysql.sock，这是因为默认的socket是在/tmp/mysql.sock

编辑/etc/my.cnf ，修改socket (client和server的都要改)

socket          = /var/lib/mysql/mysql.sock   #默认是/tmp/mysql.sock

然后重启mysql，但是shell输出：

mysqld_safe mysqld from pid file /usr/local/mysql/data/iZm5e0mgr2ayoxe7szl6i2Z.pid ended

查看mysql错误日志：

tail -f /usr/local/mysql/data/iZm5e0mgr2ayoxe7szl6i2Z.pid

报错为:

[ERROR] Do you already have another mysqld server running on socket: /var/lib/mysql/mysql.sock ?

2个原因：
/var/lib/mysql 目录不存在
/var/lib/mysql 存在，但是权限不够
创建文件夹并授权：

mkdir -p /var/lib/mysql;   # -p表示如果没有parent文件夹，就创建
chmod -R 777 /var/lib/mysql; 

重启mysql，成功。