feat: Produce a working minimal image using imagecraft in a livcd-rootfs hook

- Added manifest and filelist generation
- Currently, we only produce minimal images for amd64
- Tested the changes by booting an instance on OVH
- Hook was also tested to be run in a local CPC Jenkins pipeline

debian/changelog

@@ -1,3 +1,9 @@
+livecd-rootfs (26.04.24) resolute; urgency=medium
+
+  * Added a hook to produce a working minimal Ubuntu image using imagecraft
+
+ -- Allen Abraham <allen.abraham@canonical.com>  Tue, 03 Mar 2026 10:54:22 -0500
+
 livecd-rootfs (26.04.23) resolute; urgency=medium
 
   [ Tobias Heider ]

live-build/ubuntu-cpc/hooks.d/base/imagecraft-configs/cloud-init/etc/cloud/cloud.cfg.d/99-os_cloud.cfg

@@ -0,0 +1 @@
+datasource_list: [ OpenStack, None ]

live-build/ubuntu-cpc/hooks.d/base/imagecraft-configs/cloud-init/var/lib/cloud/seed/nocloud/meta-data

@@ -0,0 +1,2 @@
+dsmode: local
+instance_id: ubuntu-server

live-build/ubuntu-cpc/hooks.d/base/imagecraft-configs/imagecraft.yaml

@@ -0,0 +1,100 @@
+name: ubuntu-minimal
+version: "0.1"
+base: bare
+build-base: devel
+summary: Minimal Ubuntu image for CPC
+description: A minimal Ubuntu image to be built using livecd-rootfs by CPC
+
+platforms:
+  amd64:
+
+volumes:
+  pc:
+    schema: gpt
+    structure:
+      # 1. BIOS Boot
+      - name: bios-boot
+        type: 21686148-6449-6E6F-744E-656564454649
+        role: system-boot
+        filesystem: vfat
+        size: 4M
+      # 2. EFI System Partition
+      - name: efi
+        type: C12A7328-F81F-11D2-BA4B-00A0C93EC93B
+        filesystem: vfat
+        filesystem-label: UEFI
+        role: system-boot
+        size: 106M
+      # 3. Linux Extended Boot
+      - name: boot
+        type: 0FC63DAF-8483-4772-8E79-3D69D8477DE4
+        filesystem: ext4
+        filesystem-label: BOOT
+        role: system-data
+        size: 913M
+      # 4. Root Filesystem
+      - name: rootfs
+        type: 0FC63DAF-8483-4772-8E79-3D69D8477DE4
+        filesystem: ext4
+        filesystem-label: cloudimg-rootfs
+        role: system-data
+        size: 3G
+
+filesystems:
+  default:
+    - mount: "/"
+      device: "(volume/pc/rootfs)"
+    - mount: "/boot"
+      device: "(volume/pc/boot)"
+    - mount: "/boot/efi"
+      device: "(volume/pc/efi)"
+
+parts:
+  rootfs:
+    plugin: nil
+    build-packages: ["mmdebstrap"]
+    override-build: |
+      mmdebstrap --arch $CRAFT_ARCH_BUILD_FOR \
+       --mode=sudo \
+       --format=dir \
+       --variant=minbase \
+       --include=apt \
+       resolute \
+       $CRAFT_PART_INSTALL/ \
+       http://archive.ubuntu.com/ubuntu/
+      rm -r $CRAFT_PART_INSTALL/dev/*
+      mkdir $CRAFT_PART_INSTALL/boot/efi
+    organize:
+      '*': (overlay)/
+
+  packages:
+    plugin: nil
+    overlay-packages:
+      - ubuntu-server-minimal
+      - grub2-common
+      - grub-pc
+      - shim-signed
+      - linux-image-generic
+    overlay-script: |
+      rm $CRAFT_OVERLAY/etc/cloud/cloud.cfg.d/90_dpkg.cfg
+
+  snaps:
+    plugin: nil
+    after: [packages]
+    overlay-script: |
+      env SNAPPY_STORE_NO_CDN=1 snap prepare-image --classic \
+        --arch=amd64 --snap snapd --snap core24 "" $CRAFT_OVERLAY
+
+  fstab:
+    plugin: nil
+    after: [snaps]
+    overlay-script: |
+      cat << EOF > $CRAFT_OVERLAY/etc/fstab
+      LABEL=cloudimg-rootfs  /          ext4    discard,errors=remount-ro  0  1
+      LABEL=BOOT             /boot      ext4    defaults                   0  2
+      LABEL=UEFI             /boot/efi  vfat    umask=0077                 0  1
+      EOF
+
+  cloud-init:
+    plugin: dump
+    source: cloud-init/

live-build/ubuntu-cpc/hooks.d/base/imagecraft-image.binary

@@ -0,0 +1,86 @@
+#!/bin/bash -eux
+
+. config/functions
+
+ARCH="${ARCH:-}"
+SUBPROJECT="${SUBPROJECT:-}"
+
+# We want to start off imagecraft builds with just amd64 support right now
+case $ARCH in
+	amd64)
+		;;
+	*)
+	  echo "$ARCH builds for imagecraft is currently not implemented."
+		exit 0
+		;;
+esac
+
+case ${SUBPROJECT} in
+  minimized)
+    ;;
+  *)
+    echo "$SUBPROJECT builds for imagecraft is currently not implemented"
+    exit 0
+    ;;
+esac
+
+_src_d=$(dirname $(readlink -f ${0}))
+
+snap install imagecraft --classic --channel latest/edge
+apt install -y qemu-utils parted locales
+
+locale-gen C.UTF-8
+export LANG=C.UTF-8
+export LC_ALL=C.UTF-8
+
+cp -r "$_src_d"/imagecraft-configs/* .
+
+CRAFT_BUILD_ENVIRONMENT=host imagecraft --verbosity debug pack
+
+mount_image_partitions() {
+  mount_image "${disk_image}" "$ROOT_PARTITION"
+
+  # Making sure that the loop device is ready
+  partprobe "${loop_device}"
+  udevadm settle
+  ls -l "${loop_device}"*
+
+  mkdir -p "$mountpoint"
+  
+  mount_partition "${rootfs_dev_mapper}" "$mountpoint"
+  mount "${loop_device}p3" "$mountpoint/boot"
+  mount "${loop_device}p2" "$mountpoint/boot/efi"
+}
+
+install_grub_on_image() {
+  divert_grub "$mountpoint"
+  chroot "$mountpoint" grub-install --target=i386-pc "${loop_device}"
+  chroot "$mountpoint" update-grub
+  undivert_grub "$mountpoint"
+
+  echo "GRUB installed successfully."
+}
+
+unmount_image_partitions() {
+  umount "$mountpoint/boot/efi"
+  umount "$mountpoint/boot"
+
+  umount_partition "$mountpoint"
+  rmdir "$mountpoint"
+}
+
+disk_image="pc.img"
+ROOT_PARTITION=4
+mountpoint="mountpoint"
+
+mount_image_partitions
+
+install_grub_on_image
+create_manifest  "$mountpoint/" "$PWD/livecd.ubuntu-cpc.imagecraft.manifest" "$PWD/livecd.ubuntu-cpc.imagecraft.spdx"  "cloud-image-$ARCH-$(date +%Y%m%dT%H:%M:%S)" "false"
+
+unmount_image_partitions
+
+clean_loops
+trap - EXIT
+
+qemu-img convert -f raw -O qcow2 "${disk_image}" livecd.ubuntu-cpc.imagecraft.img

live-build/ubuntu-cpc/hooks.d/base/series/base

@@ -6,3 +6,4 @@ depends qcow2
 depends vmdk
 depends vagrant
 depends wsl
+depends imagecraft-image

live-build/ubuntu-cpc/hooks.d/base/series/imagecraft-image

@@ -0,0 +1,5 @@
+base/imagecraft-image.binary
+
+provides livecd.ubuntu-cpc.imagecraft.img
+provides livecd.ubuntu-cpc.imagecraft.manifest
+provides livecd.ubuntu-cpc.imagecraft.filelist