Major Changes with the V6 Stack
Engine Yard's stack V6 is the first stack to be based on Ubuntu LTS distribution. Previous stacks were based on Gentoo.
Ruby versions 2.3, 2.4, 2.5, 2,6, and 2.7 are supported. We recommend using Ruby 2.6 or 2.5. Selecting Ruby 2.3 will add 5-15 mins to instance booting since Ruby 2.3 is not included on the AMI and needs to be installed during instance booting.
Monit's use to monitor and restart processes has been reduced on V6. On this stack, monit is tracking the processes of web servers (passenger, puma, unicorn) and background jobs (resque/sidekiq). It's no longer being used for services such as redis.
The unattended-upgrades package can be used to automatically install updated packages, and can be configured to update all packages or just install security updates.Unattended upgrades are disabled by default on /etc/apt/apt.conf.d/20auto-upgrades. Set environment variable "EY_ENABLE_UNATTENDED_UPGRADES" to true to enable security updates. If you wish to utilize unattended-upgrades package differently you have to create a custom recipe to modify its configuration files. File a support ticket and we will be happy to help you configure your instances based on your requirements.
On Stack V6 you have to specifically include the Unicorn dependency in your Gemfile file as Unicorn gem is no longer provided by stack.
Consider adding the following:
Default system shell
Configuring the stack through environment variables
Stack V6 allows several options to be configured directly through environment variable, eliminating the need to use custom Chef recipes for that. Check the v6 recipes repo for details on which options are available, and this detailed KB article for how to use environment variables on EY.