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。