Podman Machine WSL OS

Source code to build and release the Fedora-based VM image for WSL.

The image is distributed as a zstd compressed .tar file for both amd64 and arm64 architectures.

The CI is triggered every 3 hours and at every push to the main branch.

At every update of the disk image:

• a new GitHub release is created and the new zstd-compressed disk images is added.
• a new OCI artifact is pushed to quay.io/podman/machine-os-wsl

Build Process Details

The source code that builds the WSL image for podman is in this Cirrus CI manifest.

To build the content of the Fedora-based disk the CI execute the following steps:

• Pulls the latest docker.io/library/fedora
• Starts a container named fedora-update and execute the commands to install Podman and other packages

After that, if the are no changes compared to the last time the CI has been executed (i.e. neither the docker.io/library/fedora image nor Podman and other packages have been updated), the build stops. When there are some changes, then a new image disk is built:

• Export the fedora-update container content to the file rootfs.tar (podman export --output rootfs.tar fedora-update)
• Remove the content of the file /etc/resolv.conf in rootfs.tar and compress it using zstd

If at least one of the 2 images (amd64 and arm64) has been updated then the CI publishes a new release:

• Creates a new GitHub release, using the build timestamp as version, and uploads the
• Push the OCI artifact to quay.io/podman/machine-os-wsl using the next version of Podman as the image tag

That's done for both amd64 and arm64 architectures. And v5.1 and v5.2 zstd files are identical.

The Delay with Podman Releases

WSL disk images build is disconnected to Podman release process.

The WSL disk image build is triggered every 3 hours and it looks for a new version of Podman. But it looks for an update on Fedora stable and that's usually updated a few days after a Podman release.

For example Podman v5.2.2 has been released on the 2024-08-21 but has been included in Fedora 40 stable one week after that, and the updated WSL disk image has been released on the 2024-08-27.

Always publish current and old version of the disk on GitHub

Podman v5.y.z downloads v5.y of the WSL OS image from the latest release on this GitHub repository. For example Podman v5.1.2 downloads the file 5.1-rootfs-amd64.tar.zst (or the arm64 equivalent) from the latest release.

That means that every GitHub release needs to include WSL disk images for old and new versions of Podman 5.

When a new version of Podman is released

When there is a new version of Podman, a new version of the Disk Image should be included in the releases:

-    # temporary 5.1, 5.2, 5.3 clone until divergance occurs
+    # temporary 5.1, 5.2, 5.3, 5.4 clone until divergance occurs
    for arch in amd64 arm64; do
      cp $VER_PFX-rootfs-$arch.tar.zst 5.1-rootfs-$arch.tar.zst
      cp $VER_PFX-rootfs-$arch.tar.zst 5.2-rootfs-$arch.tar.zst
      cp $VER_PFX-rootfs-$arch.tar.zst 5.3-rootfs-$arch.tar.zst
+     cp $VER_PFX-rootfs-$arch.tar.zst 5.4-rootfs-$arch.tar.zst
      cp $VER_PFX-latest-$arch 5.1-latest-$arch
      cp $VER_PFX-latest-$arch 5.2-latest-$arch
      cp $VER_PFX-latest-$arch 5.3-latest-$arch
+     cp $VER_PFX-latest-$arch 5.4-latest-$arch

And the OCI artifact tag should be updated using development Podman version:

-    IMAGE_TAG: "5.3"
+    IMAGE_TAG: "5.4"