#!/bin/sh

set -e

mkdir -p /tmp/rootfs
cd /tmp/rootfs

# input is a tarball of filesystem on stdin with the root filesytem
# output is a squashfs image on stdout

# extract. BSD tar auto recognises compression, unlike GNU tar
# only if stdin is a tty, if so need files volume mounted...
[ -t 0 ] || bsdtar xzf -
cd /tmp

# we want everything except the final result to stderr
(
    exec 1>&2;

    mksquashfs rootfs ./rootfs.img
)
cat rootfs.img