openwrt/target/linux/x86-2.6/image/gen_image.sh

#!/usr/bin/env bash
# Copyright (C) 2006 OpenWrt.org
set -x 
[ $# == 5 ] || {
    echo "SYNTAX: $0 <file> <kernel size> <kernel directory> <rootfs size> <rootfs image>"
    exit 1
}

OUTPUT="$1"
KERNELSIZE="$2"
KERNELDIR="$3"
ROOTFSSIZE="$4"
ROOTFSIMAGE="$5"

rm -f "$OUTPUT"

head=16
sect=63
cyl=$(( ($KERNELSIZE + $ROOTFSSIZE) * 1024 * 1024 / ($head * $sect * 512)))

# create partition table
set `ptgen -o "$OUTPUT" -h $head -s $sect -p ${KERNELSIZE}m -p ${ROOTFSSIZE}m`

KERNELOFFSET="$(($1 / 512))"
ROOTFSOFFSET="$(($2 / 512))"

BLOCKS="$((($ROOTFSOFFSET - $KERNELOFFSET) / 2 - 1))"

genext2fs -d "$KERNELDIR" -b "$BLOCKS" "$OUTPUT.kernel"
dd if="$OUTPUT.kernel" of="$OUTPUT" bs=512 seek="$KERNELOFFSET" conv=notrunc
dd if="$ROOTFSIMAGE" of="$OUTPUT" bs=512 seek="$ROOTFSOFFSET" conv=notrunc
#rm -f "$OUTPUT.kernel"

which chpax >/dev/null && chpax -zp $(which grub)
grub --batch --no-curses --no-floppy --device-map=/dev/null <<EOF
device (hd0) $OUTPUT
geometry (hd0) $cyl $head $sect
root (hd0,0)
setup (hd0)
quit
EOF