[HELP] Is there a way to add the plymouth module to dracut?

[ProbstDJakob]

I am trying to build a container image which will be deployed to bare metal machines. In order to test this first I am building a qcow2 file via bootc-image-builder and running it with qemu. In order to not scare away users with a wall of text at the start up, I would like to add a plymouth boot screen. Installing plymouth and setting the default theme is not the problem, but generating an initramfs.img containing the theme is. As far as I understand the process and bootc, initrds are generated when building the image and placed at /usr/lib/modules/<kernel-version>/initramfs.img. But no matter what I am doing, I am unable to add the dracut module plymouth. I've even tried it with a config at /usr/lib/dracut/dracut.conf.d/99-plymouth.conf containing add_dracutmodules+=" plymouth " and force_add_dracutmodules+=" plymouth ", but without luck. The output of lsinitrd stays the same and thus no plymouth boot screen appears. Besides manually adding it, if I am correct the plymouth module should already be added by default. But that is just a guess, since I do not know to what some of the variables would expand during the execution of the check function.

My question is, how to get plymouth to work and is it even possible at the moment to specify "custom" dracut modules?

[cgwalters]

(Converted to a discussion Q&A)

See https://docs.fedoraproject.org/en-US/bootc/initramfs/

I'd be sure you're listing and writing to the correct initrd location. As far as debugging dracut, it is a pain, but there's definitely nothing too bootc specific that I'm aware of. You should be able to even add a check in your container build that the expected module is there in lsinitrd (be sure you're passing the full file path in /usr/lib/modules/$kver/initramfs.img).

[ProbstDJakob]

As you may have noticed via my issue in the bootc-image-builder repo, I've got plymouth to work thanks to your hint. I miss read the docs (https://containers.github.io/bootc/bootc-images.html#kernel) and thought bootc will generate the initrd when building the qcow2 image (or to be more precise when bootc-image-builder runs bootc install to-filesystem). But with this wrong assumption out of the way, everything works as expected. No need to write anything to /usr/lib/dracut/dracut.conf.d/. Thank you.

[cgwalters]

bootc will generate the initrd when building the qcow2 image (or to be more precise when bootc-image-builder runs bootc install to-filesystem

Our philosophy in general with bootc is that your Linux system is defined at build time, and to minimize runtime computation. Hence the initramfs is always defined to come from the container image.

A different way to state this philosophy is that to the greatest extent possible, disk images are just "materialized shells" of the container content. Yes, they'll have a filesystem and block layout, but anything that is a file comes from the container image, basically.

Glad you got it working!

[ProbstDJakob]

I like this philosophy and share it personally in my own work. I always strive for achieving as much infrastructure-as-code as possible over manual configuration. That's why the GitLab Pipeline is my best friend ^^
And thanks again for helping me out.