This charm will manage a individual custom config file. Additionally it can restart a system service if the file content was changed.
juju deploy ubuntu
juju deploy configfile custommod
juju add-relation ubuntu custommod
juju config custommod filename=/etc/custommod.conf
juju config custommod restart_service=custommodd
juju config custommod content="FILE CONTENT"
This will result in a config file named /etc/custommod.conf containing "FILE CONTENT"
The content of the 'content' field is directly written in the config file. No templating or syntax check is performed.