image_to_squashfs

#!/usr/bin/bash

usage() {
cat <<EOF
Usage: $0 <diskimage> [<squashfsfile>]"

This tool converts a raw disk or filesystem image
into a by dracut bootable squashfs.

It has some logic to strip the label and bootloader from a
disk image to retrieve the filesystem.
EOF
}

info() { echo $(date +%X) $@ ; }
die() { echo $@ >&2 ; exit 1 ; }

find_first_fs_offset_kib() {
  DISKIMAGE=$1
  START_BYTES=$(parted -ms "$DISKIMAGE" unit KiB print | sed -n "/^1:/ p" | cut -d: -f2 | tr -d kiB)
  echo $START_BYTES
}

extract_first_fs() {
  DISKIMAGE=$1
  FSIMAGE=$2
  OFFSET=$(find_first_fs_offset_kib "$DISKIMAGE")
  nice ionice dd conv=sparse bs=1K skip=$OFFSET if="$DISKIMAGE" of="$FSIMAGE"
}

image_to_squashfs()
{
  SRCIMAGE=$1
  DSTIMAGE=$2

  [[ -f $SRCIMAGE ]] || die "Source image '$SRCIMAGE' does not exist."
  [[ -f $DSTIMAGE ]] && die "Destination image '$DSTIMAGE' already exists, please remove manually."
  [[ -e squashfs-root ]] && die "squashfs-root already exists, please remove manually."

  mkdir -p squashfs-root/LiveOS

  # Check if it's a disk image, then we need to remove the label
  # to get the partition, assumption: On partition

  # FIXME The size of the mbr/label is hardcoded, works by removing the label from the disk image
  [[ $(file $SRCIMAGE) =~ "boot sector" ]] && {
    info "Found a disk image, extracting the filesystem ..."
    extract_first_fs "$SRCIMAGE" "squashfs-root/LiveOS/rootfs.img"
  }

  # If the image is already afilesystem, take it directly
  [[ $(file $SRCIMAGE) =~ "filesystem" ]] && {
    info "Found a filesystem image, using this directly."
    ln -v $SRCIMAGE squashfs-root/LiveOS/rootfs.img
  }

  [[ -f squashfs-root/LiveOS/rootfs.img ]] || die "Failed to create squashfs image."

  info "Creating squashfs ..."
  mksquashfs squashfs-root $DSTIMAGE -comp xz -noappend

  info "Cleaning up"
  rm -rvf squashfs-root
}

main() {
  SRC=$1
  DST=${2:-squashfs.img}
  [[ -n $SRC ]] || die "No source given"

  image_to_squashfs $SRC $DST
}

[[ -n $@ ]] && main $@ || usage