initrd/Dockerfile

from golang:1.21.4-alpine3.18 as build

workdir /src
copy go.mod go.sum .
run go mod download

copy . .
run go test ./...
run go build -o /go/bin/init -trimpath .

# ------------------------------------------------------------------------
from alpine:3.18.4 as initrd

run apk add --no-cache xz

workdir /layer
run wget -O- https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-minirootfs-3.18.4-x86_64.tar.gz |tar zxv

run apk add --no-cache -p . musl lvm2 lvm2-dmeventd udev cryptsetup e2fsprogs btrfs-progs lsblk
run rm -rf usr/share/apk var/cache/apk

copy --from=build /go/bin/init .

# check viability
run chroot /layer /init hello

run find |cpio -H newc -o >/initrd

# ------------------------------------------------------------------------
from alpine:3.18.4
copy --from=initrd /initrd /
entrypoint ["base64","/initrd"]