Want to ensure that your services (Apache, MySQL, HHVM) on your linux instance are running 24*7? Then you can use crontab for that. This job runs every minute to check the status of the service and if it is not running then, it starts the service.
* * * * * service mysql status || service mysql start * * * * * service apache2 status || service apache2 start * * * * * service hhvm status || service hhvm start
Ctrl+O Save -> Enter -> Ctrl+X Close
service cron restart