Distrobox is an amazing tool! It allows you to run countless distros inside Podman (or Docker) on your host with the important parts of the host mounted inside. This creates a rather unforeseen problem with OCI images, they are all meant for servers, but, Distrobox is treating them more like a desktop. This means, most dedicated desktop distros do not have an image that can be used to create a container. There were two in particular I was interested in trying: Pop! OS as I am on a System76 laptop and Pop is very useful, and it's just plain better then Ubuntu, and SteamOS because I am curious to see what all the hype is about. Now, I could just bootstrap a distro with a container image to the one I want, but where's the fun in that!
# Pop OS
The simpler of the two by far was Pop! First of all, you will need to grab the ISO, from System76.
Part of what's cool about ISO images, is that you can simply mount them with sudo mount </path/to/iso> </path/to/mount-dir>.
That will give us access to the raw rootfs of the live installer for Pop! However, this is still not the rootfs of the disrto itself. For that we need to find the rootfs.squashfs. A great tool for that is fd, so simply run fd squashfs and it should look something like casper_pop-os_22.04_amd64_intel_debug_152/filesystem.squashfs. That is what we want to import into Docker/Podman, but they do not understand squashfs, so we must unsquash it with sudo unsquashfs -f -d roootfs </path/to/filesystem.squashfs>.
We now have a raw rootfs of Pop! However, we still cannot import that into Docker/Podman directly, but because we can stack together Linux tools, we can use the command sudo tar -C rootfs/ -c . | docker import - popos/latest (if you are using Podman, make sure Docker compatibility is enabled).
Now if you run podman images you will see something like localhost/popos/latest latest 2541c585efb1 23 hours ago 13.5 GB.
To create a Distrobox container using that image, simply run distrobox crate --name popos --image localhost/popos/latest.
It's certainly not the most space efficient container, but it certainly works.
# SteamOS
This one is a bit more complicated due to the fact that SteamOS 3.0 does not exactly exist yet, but that's also what makes it fun!
Fist off, grab a SteamDeck recovery image. This is an img, not an iso, so we can't just sudo mount. Instead, we need to create a loop-back device, by running sudo losetup -f -P steamdeck-recovery-4.img.
Running lsblk -f should reveal a loop device that looks something like:
loop1
├─loop1p1 vfat FAT32 esp 492E-154F
├─loop1p2 vfat FAT32 efi 4934-F915
├─loop1p3 btrfs rootfs 304d3526-c99e-45e9-81b5-b8cf4367a4a7
├─loop1p4 ext4 1.0 var 17d46966-cb62-416d-8c9d-603d5fde06c4
└─loop1p5 ext4 1.0 home 952128a7-3815-484e-9fe9-423858e036b3
We are wanting to extract the btrfs rootfs, so I would run sudo mount /dev/loop1p3 </path/to/mont-dir>.
SteamOS uses an read-only root with A/B partition updating. This does not work in a container, so run sudo cp -r rootfs/* new-rootfs, because the SteamOS image does not contain everything for Pacman to work out of the box. To ensure Pacman works, run mkdir -p new-rootfs/var/lib/pacman/local. Now import it into Podman like before by running sudo tar -C new-rootfs/ -c . | docker import - steamos/latest.
We now have a SteamOS image, but it still will not work. Why? Due to the A/B rootfs, Pacman is a bit borked in the image. So, I use the following Containerfile to force Pacman to work properly:
FROM localhost/steamos/latest
RUN pacman -Syy --noconfirm
run pacman-db-upgrade
RUN pacman -Syuu --noconfirm
RUN pacman -S --noconfirm --overwrite "*" bc curl coreutils findutils less ncurses pinentry sudo util-linux wget vte-common bash xorg
RUN chown -R root /etc
RUN userdel deck
After running podman build . I can finally create a distrobox by running distrbox create --name steamos --image <image-hash> and I have a working SteamOS distrobox.
# Known Issues:
This Containerfile is still a work in progress, and I will probably update it in the future. That said, the big issue I have noticed is Pacman giving errors along the lines of xorg-server: /usr/share/licenses/xorg-server/COPYING exists in filesystem. If this happens, just run sudo pamcan -S --noconfirm --overwrite "*" <package-name>. I am changing up the Containerfile to mitigate this in the future, but I have not done so yet.