MariaDB can be installed with the following commands on Ubuntu 16.04

apt-get update;
apt-get install mariadb-server;

Follow the Process. Type:

sudo apt-get install mariadb-server mariadb-client

Do not miss to Secure your DB:

sudo mysql_secure_installation

Enter current password for root (enter for none): Just press the Enter
Set root password? [Y/n]: Y
New password: Enter password
Re-enter new password: Repeat password
Remove anonymous users? [Y/n]: Y
Disallow root login remotely? [Y/n]: Y
Remove test database and access to it? [Y/n]: Y
Reload privilege tables now? [Y/n]: Y

Finally Restart you DB:

sudo systemctl restart mysql.service