#!/bin/sh

dev=$1
if [ -z "$dev" ]; then
	echo 'pass the device on which to install' >&2
	exit 1
fi

# try to remake boot.img if it's missing
if [ ! -f boot.img ]; then
	make || exit 1
fi

# safety check
if mount | grep ^$dev >/dev/null 2>&1; then
	echo "device $dev seems to be in use." >&2
	echo "Make sure it's the correct device, and unmount the following filesystems first:" >&2
	echo "" >&2
	mount | grep ^$dev >&2
	exit 1
fi

# copy the existing MBR to preserve the partition table
echo "saving copy of existing MBR to preserve partition table ..."
dd if=$dev of=/tmp/instmbr.mbr bs=512 count=1 status=none
echo "writing boot image to $dev ..."
dd if=boot.img of=$dev bs=512 status=none conv=notrunc
echo "patching boot sector with saved partition table ..."
dd if=/tmp/instmbr.mbr of=$dev bs=1 seek=440 skip=440 count=70 status=none conv=notrunc

sync