Comment 4 for bug 1576692

It's worth mentioning the scope of the package upgrade/install issue related to systemd.

For packages like apache2 which do not use dependent systemd service files, those service packages install and start properly.

For packages with dependent service files, like postgresql (it has both a postgresql.service (a dummy) and systemd generator service which creates a postgresql@<version>-<dbname> service; they currently do not start automatically due to being installed during cloud-init's cloud-config.service unit execution.

W.r.t package upgrades, the issue is scoped to service packages in the image which have an update that's not in the current image and also require an update to systemd services.