另类的问题所在：ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql

 

centos7 ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql

原因是硬盘满了，没有空间创建/var/lib/mysql/mysql

清理日志后启动即可。