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README-devel.md

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Developing bootupd

Currently the focus is Fedora CoreOS.

You can use the normal Rust tools to build and run the unit tests:

cargo build and cargo test

For real e2e testing, use e.g.

export COSA_DIR=/path/to/fcos
cosa build-fast
kola run -E $(pwd) --qemu-image fastbuild-fedora-coreos-bootupd-qemu.qcow2  --qemu-firmware uefi ext.bootupd.*

See also the coreos-assembler docs.

Building With Containers

Many folks use a pet container or toolbox to do development on immutable, partially mutabable, or non-Linux OS's. For those who don't use a pet/toolbox and you'd prefer not to modify your host system for development you can use the build-in-container make target to execute building inside a container.

$ make build-in-container
podman build -t bootupd-build -f Dockerfile.build
STEP 1: FROM registry.fedoraproject.org/fedora:latest
STEP 2: VOLUME /srv/bootupd
--> Using cache a033bf0e43d560e72d7187459d7fad65ab30a1d01c576e8257194d82836472f7
STEP 3: WORKDIR /srv/bootupd
--> Using cache 756114416fb4a68e72b68a2097c57d9cb94c830f5b351401319baeafa062695e
STEP 4: RUN dnf update -y &&     dnf install -y make cargo rust glib2-devel openssl-devel ostree-devel
--> Using cache a8e2b525ff0701f735e01bb5703c63bb0e67683625093d34be34bf1123a7f954
STEP 5: COMMIT bootupd-build
--> a8e2b525ff0
a8e2b525ff0701f735e01bb5703c63bb0e67683625093d34be34bf1123a7f954
podman run -ti --rm -v .:/srv/bootupd:z localhost/bootupd-build make
cargo build --release
    Updating git repository `https://gitlab.com/cgwalters/ostree-rs`
    Updating crates.io index
[...]
$ ls target/release/bootupd
target/release/bootupd
$

Integrating bootupd into a distribution/OS

Today, bootupd only really works on systems that use RPMs and ostree. (Which usually means rpm-ostree, but not strictly necessarily)

Many bootupd developers (and current CI flows) target Fedora CoreOS and derivatives, so it can be used as a "reference" for integration.

There's two parts to integration:

Generating an update payload

Bootupd's concept of an "update payload" needs to be generated as part of an OS image (e.g. ostree commit).
A good reference for this is https://github.com/coreos/fedora-coreos-config/blob/88af117d1d2c5e828e5e039adfa03c7cc66fc733/manifests/bootupd.yaml#L12

Specifically, you'll need to invoke bootupctl backend generate-update-metadata / as part of update payload generation. This scrapes metadata (e.g. RPM versions) about shim/grub and puts them along with their component files in /usr/lib/bootupd/updates/.

Installing to generated disk images

In order to correctly manage updates, bootupd also needs to be responsible for laying out files in initial disk images. A good reference for this is https://github.com/coreos/coreos-assembler/blob/93efb63dcbd63dc04a782e2c6c617ae0cd4a51c8/src/create_disk.sh#L401

Specifically, you'll need to invoke /usr/bin/bootupctl backend install --src-root /path/to/ostree/deploy /sysroot where the first path is an ostree deployment root, and the second is the physical root partition.

This will e.g. inject the initial files into the mounted EFI system partition.