# service mysqld start
Redirecting to /bin/systemctl start  mysqld.service
Failed to issue method call: Unit mysqld.service failed to load: No such file or directory.
# systemctl start mysqld.service
Failed to issue method call: Unit mysqld.service failed to load: No such file or directory.
# mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)

解决方法:

systemctl start mariadb.service
systemctl enable mariadb.service

参考资料