CLOUD_IMG_STR="# CLOUD_IMG: This file was created/modified by the Cloud Image build process"
IMAGE_SIZE=$((2252*1024**2))  # 2.2G (the current size we ship)

rootfs_dev_mapper=
loop_device=
loop_raw=

clean_loops() {
    [ -z "${rootfs_dev_mapper}" ] || {
        udevadm settle
        find /dev/mapper -iname "${loop_device///dev\//}*" | \
            xargs -n1 -I DEVICE dmsetup remove DEVICE ||
                kpartx -d "${rootfs_dev_mapper}"
        losetup -d "${loop_device}" || echo "Failed to detach disk"
        unset loop_raw
    }
}

create_empty_disk_image() {
    # Prepare an empty disk image
    dd if=/dev/zero of="$1" bs=1 count=0 seek="${IMAGE_SIZE}"
}

make_ext4_partition() {
    device="$1"

    mkfs.ext4 -F -b 4096 -i 8192 -m 0 -L cloudimg-rootfs -E resize=536870912 "$device"
}

mount_image() {
    apt-get install -qqy kpartx
    trap clean_loops EXIT
    loop_raw="$(kpartx -s -v -a "$1" )"
    loop_device="$(echo -e "${loop_raw}" | head -n1 | awk '{print($(NF-1))}')"
    rootfs_dev_mapper="/dev/mapper${loop_device///dev/}p1"
    [ ! -b "${rootfs_dev_mapper}" ] &&
        echo "${rootfs_dev_mapper} is not a block device" && exit 1
    return 0
}

mount_partition() {
    partition="$1"
    mountpoint="$2"

    mount "$partition" "$mountpoint"
    mount --bind /dev "$mountpoint/dev"
    mount proc-live -t proc "$mountpoint/proc"
    mount sysfs-live -t sysfs "$mountpoint/sys"
    mv "$mountpoint/etc/resolv.conf" resolv.conf.tmp
    cp /etc/resolv.conf "$mountpoint/etc/resolv.conf"
}

umount_partition() {
    mountpoint="$1"

    mv resolv.conf.tmp "$mountpoint/etc/resolv.conf"
    umount "$mountpoint/proc"
    umount "$mountpoint/sys"
    umount "$mountpoint/dev"
    umount "$mountpoint"
}