combine-squashfs.sh

#!/bin/bash
#
# Combine multiple squashfs files.
#
# Usage:
#
#   $ ../combine-squashfs file1.squashfs file2.squashfs …

set -xeuo pipefail

declare -a MOUNTS

unmount_all() {
  for mount in "${MOUNTS[@]}"
  do
    umount "$mount"
    rmdir "$mount"
  done
}

TARGET=$(mktemp -d)

trap unmount_all EXIT

for ARG
do
  mount="$TARGET/mount/${ARG%.squashfs}"

  mkdir -p "$mount"
  mount -o loop "$ARG" "$mount"

  MOUNTS+=("$mount")
done

mksquashfs "$TARGET/mount" "$HOME/combined-$(date +%s).squashfs"