Quadlet support for initContainers

[hluengas]

Feature request description

It seems pod initContainers are only supported manually through podman-create (using --init-ctr) or with systemd through [kube] quadlet definitions (using an initContainers definition in the supplied yaml).

It would be nice if quadlet [pod]/[container] definitions also supported this important feature.

As a user, I want to use one type of resource defintion for all my container infrastructure. To that end, native quadlet should support all the features for pods that [kube] definitions support, including initContainers.

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Suggest potential solution

I don't have much knowledge of how podman works under the hood, but as a user I would suggest that a quadlet definition for a [container] unit should have another key similar to StartWithPod like

InitContainer=true

The description for StartWithPod mentions:

If Pod= is defined, container is started by pod

The new key, InitContainer would also have a dependency on Pod= and also be a simple boolean value.

I am not sure if podman-run would also need to be changed to add initContainer support or if quadlet changes alone are sufficient.

As I understand, [pod] & [container] quadlet units utilize podman-run, while [kube] units utilize podman-kube-play.

podman-kube-play supports initContainers, but podman-run does not. In native podman this is only supported using podman-create.

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Have you considered any alternatives?

I am aware what I want to do can be achieved with [kube] quadlet units but i think this feature should be available with [container] & [pod] units also.

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Additional context

For some context I previously defined all my container infrastructure using [kube] systemd/quadlet definitions as it seemed like the most clean and portable way, but eventually I encountered some podman functionality that wasn't well supported using this method.

For example I struggled to get GPU access working in a rootless container using a [kube] definition but was able to use the combination of --device and --group-add keep-groups with a the [pod] and [container] defintions.

Because of this I bit the bullet and swithced to using the pure quadlet definitons, because it seemed that kube-play support is more of a compatability after thought.

Now I find myself needing to setup a pod with a certbot initContainer, and of course I want to use systemd to manage the lifecycle of the pod, but it seems this is only possible using a [kube] quadlet definition.

The only other issue I found for this Vrothberg mentions:

"I agree. podman generate systemd shouldn't receive new features as our focus lies on Quadlet which supports running Pods by means of Kubernetes YAML."