Now we've come to the fun part, installing MariaDB. To get the ball rolling, we'll install the mariadb-server package:
# apt-get install mariadb-server
If your organization prefers to stick with MySQL, the package to install is mysql-server instead:
# apt-get install mysql-server
Note
I don't recommend switching from MariaDB to MySQL (or vice versa) on the same server. I've seen some very strange configuration issues occur on servers that had one installed and then were switched to the other (even after wiping the configuration). For the most part, it's best to pick one and stick with it. As a general rule, MySQL should only be used if you have legacy databases to support. For brand-new installations, go with MariaDB.
Going forward, I'll assume that you've installed MariaDB, though the instructions here shouldn't differ between them. Normally, you'd probably use the systemctl command at this point to investigate whether or not the MariaDB daemon has started and is running...