umount-root-6 (was Re: [PATCH] root-hopping for pre-2.3.41-3)

From: almesber@lrc.di.epfl.ch
Date: Wed Jan 26 2000 - 02:04:49 EST


I wrote:
> Sigh, a new system call then :-(

Done ;-) I've attached the patch for pre-2.3.41-3 (also works with
2.3.40) and pivot_root.c . The complete package with examples is at
ftp://icaftp.epfl.ch/pub/people/almesber/misc/umount-root-6.tar.gz

Changes: /proc/mounts skips unreachable mount points, and quota is "dumb"
again. Umount flags are gone. Instead, there's a pivot_root system call
(with implicit global chroot), similar to what Peter suggested.

Concerning unreachable mount points: you can still get them by pivoting a
directory which is not a mount point itself, e.g. if you mount /iRoot and
/iRoot/opaque_office_beige, and then you pivot_root to
/iRoot/transp_light_yellow, /proc/mounts doesn't show
/iRoot/opaque_office_beige anymore. However, it "knows" that /iRoot is
special and shows it as /. I you pivot_root /sth /sth/junk again, all
that mess comes back under /junk/iRoot, as it should. So basically all
cases that make any sense in real life look pretty normal.

Cheers, Werner

-- 
  _________________________________________________________________________
 / Werner Almesberger, ICA, EPFL, CH       werner.almesberger@ica.epfl.ch /
/_IN_N_032__Tel_+41_21_693_6621__Fax_+41_21_693_6610_____________________/



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