extract-alarmpi

# SOURCE is a .tar.gz file containing arch linux for raspberry pi
UPSTREAM_SOURCE="ArchLinuxARM-rpi-latest.tar.gz"
UPSTREAM_URL="http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-latest.tar.gz"
if [ "$1" = "-h" ]
then
    echo "Usage: extract-alarmpi [SOURCE [TARGET [SIZE]]]" >/dev/stderr
    echo "       SOURCE should be a .tar.gz file"
    echo "       SIZE is specified in gigabytes (10^9 bytes)"
fi

if [ -n "$1" ]
then
    SOURCE=$1
else
    echo "Downloading latest Arch Linux ARM distribution..."
    wget -N "${UPSTREAM_URL}"
    SOURCE="${UPSTREAM_SOURCE}"
fi
# TARGET is a .img binary file
TARGET=image
[ -n "$2" ] && TARGET=$2 
# SIZE in bytes
SIZE=$((1000*1000*1000*8)) # 8G
[ -n "$3" ] && SIZE=$((1000*1000*1000*${3}))
shift 3
LOOP_DEVICE=/dev/loop0

modinfo loop | grep -q max_part || {
    echo "You must modprobe 'loop' so it is loaded with 'max_part=2' or greater"
    exit 1
}

# Delete any existing image
rm -f "$TARGET"
# Make a file filled with zeros
dd if=/dev/zero of="$TARGET" bs=1024 count=$((SIZE/1024))
sync
losetup ${LOOP_DEVICE} "${TARGET}" || exit 1
# Format the disk to have a FAT32 partition and then an ext4 partition
fdisk "${LOOP_DEVICE}" <<EOF
o
p
n
p
1

+100M
t
c
n
p
2


w
EOF
BOOT_DEVICE="${LOOP_DEVICE}p1"
ROOT_DEVICE="${LOOP_DEVICE}p2"
mkfs.vfat ${BOOT_DEVICE}
mkfs.ext4 ${ROOT_DEVICE}

mkdir /tmp/boot /tmp/root

mount ${BOOT_DEVICE} /tmp/boot
mount ${ROOT_DEVICE} /tmp/root
bsdtar -xpf "${SOURCE}" -C /tmp/root
mv /tmp/root/boot/* /tmp/boot

umount /tmp/boot /tmp/root
rmdir /tmp/root /tmp/boot
sudo losetup -d "${LOOP_DEVICE}"

# Reproducible build
touch -r "${SOURCE}" "${TARGET}"
# Set the file to be owned by the real user and not root
chown ${SUDO_UID:-$(id -r -u)}:${SUDO_GID:-$(id -r -g)} "${TARGET}"