This is a self deploying container for running a Univention Corporate Server (UCS) with the role of primary, backup, replica directory node or managed node.
First fo all, you have to understand the structure of all the important running parts. The container starts with the process identifier ( PID ) number one by the command/entrypoint /bin/systemd or better systemd. From now controlls systemd all type of service units and will start a service unit called univention-container-mode-firstboot for the first start/boot process with some depencies like the environment service unit univention-container-mode-environment. The same applies to the service unit univention-container-mode-pre-installed-role. But much faster, because almost all packages are already installed.
| ID | TYPE AND DESCRIPTION |
|---|---|
| 00 | system and defaults |
| 10 | free to use |
| 20 | - |
| 30 | service units preprocessing |
| 40 | setup preprocessing |
| 50 | setup and join processing |
| 60 | setup postprocessing |
| 70 | service units postprocessing |
| 80 | - |
| 90 | free to use |
| 99 | system and cleanups |
A closer look into univention-container-mode-firstboot will explain that the command ( run-parts --verbose -- join ) runs all scripts from the join directory. Finaly copy, rename and modify the template into the directory root/usr/lib/univention-container-mode/join/ and run your own container build to deploy the new feature on your local registry.