Adjust role for buliding AMIs with Packer

[tomaszkiewicz]

Hi,

I've added a little switch I use often in Ansible for building AMI packages in AWS using Packer tool.
The thing is that while building we don't want to start the services, because they are often in unconfigured state, so setting start_services to false prevents that.

The default behaviour is unchanged, so running playbook with this role installs and starts filebeat.

The other thing I've added (only for RedHat, as I know how to do it in RH) is the environment file reference for systemd file - this is to be used in templates, where you can use env variables for dynamic configuration of filebeat.

Best regards

Łukasz Tomaszkiewicz

[andyshinn]

This would probably make sense as a drop-in unit instead of modifying the unit directly: https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Description

Along with a unit file foo.service, a "drop-in" directory foo.service.d/ may exist. All files with the suffix ".conf" from this directory will be parsed after the unit file itself is parsed. This is useful to alter or add configuration settings for a unit, without having to modify unit files.