Since Drupal VM is built in a modular fashion, and the upstream Ansible Role that installs and configures MySQL is built in a way that works with any MySQL-compatible replacement, you can easily swap out MySQL for MariaDB.
The simplest way is to add the following lines after the
# MySQL Configuration. line in
mysql_packages: - mariadb-client - mariadb-server - python-mysqldb
This set of packages works out of the box with Ubuntu 14.04 as well as the default Ubuntu 16.04 installation that comes with Drupal VM.
Alternatively, if you want to use RedHat 7 or CentOS 7 instead of Ubuntu, you can set the following variables to install and configure MariaDB instead of MySQL:
mysql_packages: - mariadb - mariadb-server - mariadb-libs - MySQL-python - perl-DBD-MySQL mysql_daemon: mariadb mysql_socket: /var/lib/mysql/mysql.sock mysql_log_error: /var/log/mariadb/mariadb.log mysql_syslog_tag: mariadb mysql_pid_file: /var/run/mariadb/mariadb.pid