scripts/combined-image.sh

   1 #!/bin/sh
   2
   3 BLKSZ=65536
   4
   5 [ -f "$1" -a -f "$2" ] || {
   6         echo "Usage: $0 <kernel image> <rootfs image> [output file]"
   7         exit 1
   8 }
   9
  10 # Make sure provided images are 64k aligned.
  11 kern=$(mktemp)
  12 root=$(mktemp)
  13 dd if="$1" of="$kern" bs=$BLKSZ conv=sync 2>/dev/null
  14 dd if="$2" of="$root" bs=$BLKSZ conv=sync 2>/dev/null
  15
  16 # Calculate md5sum over combined kernel and rootfs image.
  17 md5=$(cat "$kern" "$root" | md5sum -)
  18
  19 # Write image header followed by kernel and rootfs image.
  20 # The header is padded to 64k, format is:
  21 #  CI               magic word ("Combined Image")
  22 #  <kernel length>  length of kernel encoded as zero padded 8 digit hex
  23 #  <rootfs length>  length of rootfs encoded as zero padded 8 digit hex
  24 #  <md5sum>         checksum of the combined kernel and rootfs image
  25 ( printf "CI%08x%08x%32s" \
  26         $(stat -c "%s" "$kern") $(stat -c "%s" "$root") "${md5%% *}" | \
  27         dd bs=$BLKSZ conv=sync;
  28   cat "$kern" "$root"
  29 ) > ${3:-openwrt-combined.img} 2>/dev/null
  30
  31 # Clean up.
  32 rm -f "$kern" "$root"