bootc is a great project, and I really like the idea of "Boot and upgrade via container images". However, due to the developement history bootc is highly related with ostree and many other projects.
bootd would provide a simple way just rely on systemd / drucat / grub / composefs make boot from container image as simple as possible.
It only handles mount oci composefs as sysroot.
The final goal is merged back to bootc project.
There are three parts
- build: build image from Containerfile, need handle kernel/initramfs(dracut)
- deploy: grub bls BootLoaderSpec
- boot: dracut module
bootc don't support the way https://github.com/containers/bootc/blob/main/docs/src/bootc-images.md
FROM fedora
RUN dnf -y install kernel
But this way is really simple and can adoptable for most distroful Containerfile. In order to boot, bootd still need add few requirements.
Containerfile
- require composefs
- cfs-prepare-sysroot
- kernel / initramfs (dracut)
ARG base=docker.io/library/ubuntu:rolling
FROM $base as composefs
# prepare composefs
FROM $base
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y systemd ostree dracut
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y linux-image-generic
COPY --from=composefs /cfs/target/usr /usr
RUN mkdir -p /usr/lib/dracut/modules.d
COPY dracut.d /usr/lib/dracut/modules.d/80cfs-prepare-root
...
podman build -t localhost/bootc-ubuntu:latest . -f images/Containerfile.ubuntu
podman image mount localhost/bootc-ubuntu:latest
ln -s sysroot/composefs composefs
/var/lib/containers/storage/overlay/98cf94224120f2355d5efc4df25632f6789c3b251f52cc0893562f959d72a7f6/merged
mkcomposefs /var/lib/containers/storage/overlay/98cf94224120f2355d5efc4df25632f6789c3b251f52cc0893562f959d72a7f6/merged --digest-store=/sysroot/composefs/repo /sysroot/composefs/images/bootc-cs9.cfs