mk-firecracker

#!/bin/bash

usage() {
	echo -e "mk-firecracker -s <SIZE> -i <QCOW2_IMG> -p <ROOT_PART>"
	echo -e "options:"
	echo -e "\t-s : size of final ext4 file in GB (eg -s 4 == 4GB)"
	echo -e "\t-i : QCOW2 image to transform"
	echo -e "\t-p : Partition where the filesystem is kept in QCOW2_IMG"
	echo -e "\n\texample:\n\t$ mk-firecracker -s 10 -i arch.qcow2 -p 3\n"
}

SIZE=""
QEMU_IMG=""
PART=""

while [[ ! -z "$1" ]]; do
	case "$1" in
		-h|--help)
			usage
			exit 1
			;;
		-s|--size)
			SIZE=$2
			shift
			;;
		-i|--img)
			QEMU_IMG=$2
			shift
			;;
		-p|--partition)
			PART=$2
			shift
			;;
	esac
	shift
done

ID=$(id | awk '{ print $1; }' | cut -b 5-8 | sed 's/[^0-9]*//g')
if [[ $ID != "0" ]]; then
	echo -e "Error: Must be root"
	exit 1
fi

if [[ $SIZE == "" || $QEMU_IMG == "" || $PART == "" ]]; then
	echo -e "ERROR: Missing parameter"
	usage
	exit 1
else
	echo -e "size = $SIZE image = $QEMU_IMG partition = $PART"
fi

BASE=`pwd`
EXT=$BASE/ext4-dir

umount ext4-dir 2> /dev/null
umount raw-dir 2> /dev/null
rm -rf ext4-dir raw-dir 2> /dev/null
mkdir ext4-dir raw-dir

rm OS.ext4 2> /dev/null
dd if=/dev/zero of=OS.ext4 bs=1G count=$SIZE
mkfs.ext4 OS.ext4

LOOP_0=`losetup -f`
losetup -fP OS.ext4
mount $LOOP_0 ext4-dir

LOOP_1=`losetup -f`
LOOP_1+="p$PART"

isqemu=$(file $QEMU_IMG | grep -i "qemu qcow")
if [[ ! -z "$isqemu" ]]; then
	rm $QEMU_IMG.raw 2> /dev/null
	qemu-img convert -f qcow2 -O raw $QEMU_IMG $QEMU_IMG.raw
	QEMU_IMG="$QEMU_IMG.raw"
fi

losetup -fP $QEMU_IMG
mount "$LOOP_1" raw-dir

cd raw-dir
#cd root
tar c . | tar x -C $EXT
cd $BASE
rm -rf ext4-dir/lost+found
rm ext4-dir/etc/fstab
touch ext4-dir/.autorelabel
ls -l ext4-dir

umount raw-dir
umount ext4-dir
losetup -d $LOOP_1
losetup -d $LOOP_0
rm -rf raw-dir ext4-dir