if [ "$0" == "chroot.sh" ]; then
 echo Do not execute this, source it instead: "source $0" >&2
 exit 1
fi
root_dir=$(readlink -f $(pwd))
if [ -z "$CHROOTER" ]; then
 CHROOTER=$USER
fi
echo Will chroot to $root_dir then become user $CHROOTER >&2
if [ "$root_dir" == "/opt/wheezy64" ]; then
 sudo mount -t proc proc proc/
 sudo mount -t sysfs sys sys/
 sudo mount -o bind /dev dev/
 sudo mount -t devpts devpts dev/pts
 sudo mount -o bind /media/sda3 media/sda3
 sudo mount -o bind /home/jcomeau home/jcomeau
 sudo chroot . /bin/bash -c "su - $CHROOTER"
 # upon exit from chroot, undo the mounts
 sudo umount home/jcomeau
 sudo umount media/sda3
 sudo umount dev/pts
 sudo umount dev
 sudo umount sys
 sudo umount proc
else
 echo Unexpected root directory $root_dir, nothing done >&2
fi