#!/bin/sh

# Copyright (C) 2005-2010 Junjiro R. Okajima
#
# This program, aufs is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#set -x
tmp=/tmp/$$
set -e

test $# -eq 0 -o "$1" = "-help" -o "$1" = "--help" &&
cat << EOF 1>&2 && exit 1
usage: $0 dir [command]
Makes a jail or chrooted environment under the given dir for the given
command such as chroot(8), but it is based upon AUFS.
If you want to hide/modify something under /, then remove/modify it
under AUFS or customize this script.

This script includes a sample customization for apache on debian
system. e.g. "sudo sh ./auroot.sh /tmp/jail /etc/init.d/apache2 start"
EOF

dir="$1"
mkdir -p "$dir" "$tmp"
mount -t tmpfs none "$tmp"

# a sample for generic mount
#mount -o ro,rbind / $tmp.ro
#mount -t aufs -o br:$tmp.rw:$tmp.ro aufs "$dir"

# a sample for my test system,
# which has /, /dev, /var and /usr on separated partitions for each.
f()
{
	mntpnt="$1"
	name="$2"
	rw="$tmp/rw.$name"

	mkdir -p "$rw"
	mount -t aufs -o br:"$rw":"$mntpnt"=ro aufs "$dir$mntpnt"
}

f / root
for i in dev var usr
do
	f /$i $i
done

# a sample for apache2 on debian
f="$dir/etc/default/apache2"
test -w $f && echo 'NO_START=0' >> $f

exec chroot "$@"