Make Ubuntu Cloud images bootable in virtualbox. Pre-requirements: qemu-img (package qemu-utils in Ubuntu repo), extlinux Tested under Ubuntu 13.04, might work on other linux distros. Get ubuntu image: http://cloud-images.ubuntu.com/precise/current/*.img

ubuntu-cloud-bootable.sh

#!/bin/bash
##
## Usage: sudo ubuntu-cloud-bootable.sh precise-server-cloudimg-amd64-disk1.img
##

set -e

mount_point="$(mktemp -d)"
raw="$(mktemp)"
echo ">>> Converting to raw: $raw ..."
qemu-img convert -O raw "$1" "$raw"
echo ">>> Installing bootloader..."
offset=$(fdisk -l "$raw" | grep -E "${raw}p?1" | awk '{print $3}')
mount -o loop,offset=$(($offset * 512)) "$raw" "$mount_point"
mkdir "$mount_point/extlinux/"
extlinux --install "$mount_point/extlinux/"
echo "DEFAULT /vmlinuz" > "$mount_point/extlinux/extlinux.conf"
echo "APPEND root=/dev/sda init=/usr/lib/cloud-init/uncloud-init" \
     "ubuntu-pass=ubuntu ds=nocloud" >> "$mount_point/extlinux/extlinux.conf"
umount "$mount_point"
rmdir "$mount_point"
echo ">>> Converting to vdi..."
vdi="$(dirname "$1")/$(basename "$1" .img)-bootable.vdi"
qemu-img convert -O vdi "$raw" "$vdi"
rm "$raw"
chown --reference="$1" "$vdi"
echo "Image ready: $vdi"