home/files/bin/do_chroot

#!/bin/sh

arg0=$(basename "$0")

fatal() {
	echo "F: $arg0: $@"
	exit 1
}

if [ $# -gt 0 -a -d "$1" ]; then
	DIR="$1"
	shift
else
	DIR="."
fi


cd "$DIR" || fatal "$DIR: invalid chroot dir"
DIR=$(pwd -P)

error=false
for x in dev dev/pts proc sys tmp; do
	if ! grep -q " $DIR/$x " /proc/mounts; then
		mount --bind /$x $DIR/$x || error=true

		if $error; then
			[ "$x" != dev ] || fatal "can't do anything"
			break
		fi
	fi
done

$error || chroot "$DIR" "$@"

while grep -q " $DIR/" /proc/mounts; do
	sleep 0.2
	grep " $DIR/" /proc/mounts | cut -d' ' -f2 | tac | xargs -r --verbose -- umount
done