Looking at this with fresh eyes (good morning), I've realised that by putting this line in the `common.yaml` file, this setting for SFTP will apply to all machines using this Puppet repo.

For this to apply only to a specific machine, you would need to include this line in a YAML file specific to that machine. Looking in the [hiera.yml](https://github.com/alphagov/ci-puppet/blob/master/hiera_production.yaml#L1-L7) file, this would be named along the lines of `role.%{::machine_role}.yaml` or `role.%{::machine_role}.%{::machine_id}.yaml`. Feel free to give me a shout if you're unsure about this.