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#!/bin/sh
BLKSZ=65536
[ -f "$1" -a -f "$2" ] || {
echo "Usage: $0 <kernel image> <rootfs image> [output file]"
exit 1
}
# Make sure provided images are 64k aligned.
kern=$(mktemp)
root=$(mktemp)
dd if="$1" of="$kern" bs=$BLKSZ conv=sync 2>/dev/null
dd if="$2" of="$root" bs=$BLKSZ conv=sync 2>/dev/null
# Calculate md5sum over combined kernel and rootfs image.
md5=$(cat "$kern" "$root" | md5sum -)
# Write image header followed by kernel and rootfs image.
# The header is padded to 64k, format is:
# CI magic word ("Combined Image")
# <kernel length> length of kernel encoded as zero padded 8 digit hex
# <rootfs length> length of rootfs encoded as zero padded 8 digit hex
# <md5sum> checksum of the combined kernel and rootfs image
( printf "CI%08x%08x%32s" \
$(stat -c "%s" "$kern") $(stat -c "%s" "$root") "${md5%% *}" | \
dd bs=$BLKSZ conv=sync;
cat "$kern" "$root"
) > ${3:-openwrt-combined.img} 2>/dev/null
# Clean up.
rm -f "$kern" "$root"
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