ubuntu-cloud-image/build.sh

#!/bin/bash

OS_CODENAME=focal
OS_VERSION=20.04
DEV=/dev/nbd0
TYPE=cloud
DOWNLOAD=yes
MAAS_ID=20220524

if [ ${TYPE} == cloud ]; then
	ROOTPART="${DEV}p1"
else
	BOOTPART="${DEV}p1"
	ROOTPART="${DEV}p2"
fi

function download(){
	if [ -z "$DOWNLOAD" ]; then
		return
	fi
	echo "Downloading"
	if [ ${TYPE} == "cloud" ]; then
		wget -O build/${TYPE}/initrd.img \
			https://cloud-images.ubuntu.com/$OS_CODENAME/current/unpacked/${OS_CODENAME}-server-cloudimg-amd64-initrd-generic
		wget -O build/${TYPE}/vmlinuz \
			https://cloud-images.ubuntu.com/${OS_CODENAME}/current/unpacked/${OS_CODENAME}-server-cloudimg-amd64-vmlinuz-generic
		wget -O build/${TYPE}/rootfs.tar.xz \
			https://cloud-images.ubuntu.com/${OS_CODENAME}/current/${OS_CODENAME}-server-cloudimg-amd64-root.tar.xz
	else
		wget -O build/${TYPE}/initrd.img \
			https://images.maas.io/ephemeral-v3/stable/${OS_CODENAME}/amd64/${MAAS_ID}/ga-${OS_VERSION}/boot-initrd
		wget -O build/${TYPE}/vmlinuz \
			https://images.maas.io/ephemeral-v3/stable/${OS_CODENAME}/amd64/${MAAS_ID}/ga-${OS_VERSION}/boot-kernel
		wget -O build/${TYPE}/rootfs.squashfs \
			https://cloud-images.ubuntu.com/${OS_CODENAME}/amd64/${MAAS_ID}/squashfs
fi
}

sudo apt -yq install syslinux syslinux-common syslinux-efi extlinux f2fs-tools

mkdir -p build/${TYPE} mnt out squashmount

download

KERNEL_VERSION="$(file build/${TYPE}/vmlinuz |cut -d, -f2|cut -d\  -f3)"
echo "Detected kernel ${KERNEL_VERSION}"

echo "Creating empty image"
qemu-img create -f qcow2 build/${TYPE}/ubuntu-${OS_CODENAME}.qcow2 2G || exit 1

echo "attaching image"
sudo modprobe nbd
sudo qemu-nbd -c "${DEV}" build/${TYPE}/ubuntu-${OS_CODENAME}.qcow2 || exit 1

echo "partitioning"
sudo parted -s "${DEV}" -- \
        mklabel gpt \
        unit MiB \
        mkpart '"Ubuntu"' btrfs 1 100% \
        set 1 legacy_boot on
until [ -b "${DEV}1" ] || [ -b "${DEV}p1" ]; do
   sleep 1
done


echo "installing hybrid bootloader"
sudo dd bs=440 count=1 conv=notrunc \
   if=/usr/lib/syslinux/mbr/gptmbr.bin of="$DEV" 2> /dev/null
sync

if [ ${TYPE} == "cloud" ]; then
	echo "mkfs.btrfs"
	sudo mkfs.btrfs -L rootfs ${ROOTPART}" || exit 1
else
	echo "mkfs.btrfs"
	sudo mkfs.btrfs -L boot ${BOOTPART}" || exit 1
	echo "mkfs.f2fs"
	sudo mkfs.f2fs -l rootfs -O extra_attr,inode_checksum,sb_checksum,compression ${ROOTPART} || exit 1
fi
sync

echo "mounting root"
if [ ${TYPE} == "cloud" ]; then
	sudo mount -t btrfs ${ROOTPART} mnt || exit 1
else
	sudo mount -t f2fs ${ROOTPART} mnt || exit 1
	sudo mkdir -p mnt/boot
	sudo mount -t btrfs ${BOOTPART} mnt/boot || exit 1
fi

echo "unpacking root fs"
if [ ${TYPE} == "cloud" ]; then
	sudo tar xJf build/${TYPE}/rootfs.tar.xz -C mnt || exit 1
else
	sudo mount -t squashfs build/${TYPE}/rootfs.squashfs squashmount -o ro,loop || exit 1
	cp -ar squashmount/. mnt
fi

echo "installing kernel and inintd"
sudo mkdir -p mnt/boot
sudo cp -ar build/${TYPE}/initrd.img "mnt/boot/initrd.img-${KERNEL_VERSION}"
sudo cp -ar build/${TYPE}/vmlinuz "mnt/boot/vmlinuz-${KERNEL_VERSION}"
sudo ln -s "vmlinuz-${KERNEL_VERSION}" mnt/boot/vmlinuz
sudo ln -s "initrd.img-${KERNEL_VERSION}" mnt/boot/initrd.img

echo "installing legacy syslinux files"
sudo mkdir -p mnt/boot/syslinux
sudo cp /usr/lib/syslinux/modules/bios/*.c32 mnt/boot/syslinux/
sudo cp syslinux/{mainmenu,syslinux}.cfg mnt/boot/syslinux
if [ -n "$1" ]; then
    echo "Patching UUID $1"
    sudo sed -i -e "s/?/?uuid=$1\&/g" mnt/boot/syslinux/mainmenu.cfg
    cat mnt/boot/syslinux/mainmenu.cfg
fi

echo "here is the fstab"
if [ ${TYPE} == "cloud" ]; then
	echo "LABEL=rootfs / btrfs defaults 0 1" | sudo tee mnt/etc/fstab
else
	echo "LABEL=rootfs / f2fs defaults 0 1" | sudo tee mnt/etc/fstab
	echo "LABEL=boot /boot btrfs defaults 0 1" | sudo tee -a mnt/etc/fstab
fi

echo "installing syslinux bootloader"
sudo extlinux -i mnt/boot/syslinux

echo "umounting"
sync
if [ ${TYPE} != "cloud" ]; then
	umount /mnt/boot
fi
sudo umount mnt

echo "detaching"
sudo qemu-nbd -d "${DEV}"

echo "compressing"
qemu-img convert -cpO qcow2 build/${TYPE}/ubuntu-${OS_CODENAME}.qcow2 out/ubuntu-${OS_CODENAME}-${TYPE}.qcow2
# rm -f out/ubuntu-${OS_CODENAME}.qcow2

echo "done"