Debian / Ubuntu using System V init scripts:

• service mysql restart

Debian / Ubuntu using systemd:

• systemctl enable mysql.service
• systemctl restart mysql.service

Devuan:

• service mysql restart

CentOS 7 and later:

• systemctl enable mariadb.service
• systemctl start mariadb.service

CentOS 6 and earlier, Fedora, and Redhat:

• chkconfig mysqld on
• service mysqld start