The official dokku/dokku image gains a HEALTHCHECK directive backed by a loopback-only HTTP endpoint at `127.0.0.1:18080/_dokku/health`. The endpoint reports 200 once first-boot bootstrap finishes, sshd and nginx are accepting connections, and `dokku ps:restore` completes; otherwise it returns 503. Changes are scoped to the Docker overlay and Dockerfile so debian-package installs are unaffected.
During docker image generation, certain folders either do not exist or are symlinked in an odd fashion, causing the install trigger to fail. This is not the case at runtime, so we should defer the install trigger until container start and provide a method of skipping it when generating a docker image.
Closes#7308
When deploying the Dokku via Docker, ssh keys are added directly via the ssh-keys:add command, and thus we can skip this step completely (as there won't be a public key in that path).
On newer Ubuntu Noble, cron (among other things) has a transitory dependency on systemd, forcing our systemd/runit detection to fail. This change allows overriding the detected init on Ubuntu systems, ensuring we always do the right thing when interacting with init.
This change allows supporting the openresty package as installed on Ubuntu 18.04 from the official openresty package repository, while also returning general nginx support.
Closes#3675
