#!/bin/sh
DIR="$1"
[ -z "${DIR}" ] && exit 1 
#if ! grep -q overlay /proc/filesystems
#then
#    echo "Filesystem overlay is not available. You need a kernel update: apt-get update && apt-get upgrade"  >&2
#    exit 2
#fi
if [ ! -d "${DIR}_org" ]
then
    echo "${DIR}_org does not exist" >&2
    exit 1
fi
if [ ! -d "${DIR}_rw" ]
then
    echo "${DIR}_rw does not exist" >&2
    exit 1
fi
#
# ro must be the first mount option for root .....
#
#ROOT_MOUNT=$( grep -v "^#" /etc/fstab | awk '$2=="/" { print substr($4,1,2) }' )
ROOT_MOUNT=$( awk '$2=="/" { print substr($4,1,2) }' /proc/mounts )

if [ "$ROOT_MOUNT" != "ro" ]; then
    /bin/mount --bind ${DIR}_org ${DIR}
else
    /bin/mount -t tmpfs ramdisk ${DIR}_rw
    /bin/mkdir ${DIR}_rw/upper
    /bin/mkdir ${DIR}_rw/work
    OPTS="-o lowerdir=${DIR}_org,upperdir=${DIR}_rw/upper,workdir=${DIR}_rw/work"
    /bin/mount -t overlay ${OPTS} overlay ${DIR}
fi