# update system:
sudo apt-get update
sudo apt-get dist-upgrade
# install mysql server and client
sudo apt-get install mysql-server mysql-client
# set up a root password
sudo mysqladmin -u root -h localhost password [password]
sudo mysqladmin -u root -h myhostname password [password] # if used non-locally
# install mysqli extension (mysql is removed from PHP7)
sudo apt-get install php7.0-mysql
# access mysql directly from CLI
mysql -u root -p