Horst von Brand wrote:
> What about mounts under the (now old) root? What if /new_root/usr doesn't
> exist, is not a directory, has something else mounted? What happens with
> open /dev/whatever?
Wrong approach: too complex, too intrusive, too unreliable.
Just changing root and cwd if they are exactly at the root of the file
system covers 99.9% of the useful cases. Things that access anything else
are likely to have a strong dislike to being "rerouted", because then you
also have to touch the inode. Think of /var/log/syslog becoming
/elsewhere/var/log/syslog, or subtle cases like
ln /dev/tty0 /dev/console vs. cd /elsewhere/dev; ln ttyS0 console
No, let's keep this simple. If you try to root-hop a fully running
system, you're almost guaranteed that something will get in the way, or
that you'll screw up something's assumptions in a subtle but
disastrous way. So it's not worth even trying.
On the other hand, changing root and cwd iff at the old root, while
already a bit hackish, still gives predictable semantics, e.g. from the
perspective of the process experiencing the forced chroot, this is
pretty much equivalent to root doing an rm -rf / followed by
re-populating / with some other content. A bit rude perhaps, but
something that could happen in the real world. (Unlike a VC becoming a
serial port, file, etc.)
- Werner
-- _________________________________________________________________________ / Werner Almesberger, ICA, EPFL, CH werner.almesberger@ica.epfl.ch / /_IN_N_032__Tel_+41_21_693_6621__Fax_+41_21_693_6610_____________________/- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Jan 31 2000 - 21:00:16 EST