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Embedding MicroShift Container Images for Offline Deployments

Image Builder supports building rpm-ostree system images with embedded container images. Embedded container images are immediately available to container engines like podman and cri-o after booting the system, without having to pull images over the network from a container registry. This means container workloads can start up without delay and without requiring network connectivity.

To embed a container image, add it to the Image Builder blueprint as follows:

[[containers]]
source = "<your_image_pullspec_with_tag_or_digest>"

To embed MicroShift container images, you need to know the exact list of container image references used by the MicroShift version you are deploying. You can obtain this list by installing the microshift-release-info RPM package of the same version, for example:

$ sudo dnf install -y microshift-release-info-4.12.0-1
$ ls /usr/share/microshift/release
release-aarch64.json  release-x86_64.json

Alternatively, you can download and unpack the RPM package without installing it:

$ sudo dnf download microshift-release-info-4.12.0-1
microshift-release-info-4.12.0-1.el8.noarch.rpm
$ rpm2cpio microshift-release-info-4.12.0-1.el8.noarch.rpm | cpio -idmv
./usr/share/microshift/release/release-aarch64.json
./usr/share/microshift/release/release-x86_64.json

Using the release info for your CPU architecture, you can now generate the section to embed the container images to your blueprint.toml:

$ jq -r '.images | .[] | ("[[containers]]\nsource = \"" + . + "\"\n")' release-$(uname -m).json >> blueprint.toml

Remember to pin the version of the MicroShift RPMs in the blueprint to the version matching your container images. The resulting blueprint.toml should look similar to this:

name = "microshift-offline"

description = ""
version = "0.0.1"
modules = []
groups = []

[[packages]]
name = "microshift"
version = "4.12.0-1"

[[containers]]
source = "quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:9945c3f5475a37e145160d2fe6bb21948f1024a856827bc9e7d5bc882f44a750"

[[containers]]
source = "quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:82cfef91557f9a70cff5a90accba45841a37524e9b93f98a97b20f6b2b69e5db"

...

You need to add a pull secret for authenticating to the registry. To do so, set the auth_file_path in the [containers] section of the osbuilder worker configuration in /etc/osbuild-worker/osbuild-worker.toml (you might need to create directory and file).

[containers]
auth_file_path = "/etc/osbuild-worker/pull-secret.json"

You need to restart the osbuild-worker when you changed that configuration using sudo systemctl restart osbuild-worker@1

Refer to the Container registry credentials section of the osbuild guide for more details.

Now you can composer-cli blueprint push ... the modified blueprint and composer-cli compose start ... the build as usual. The resuling commit will have the images embedded.