Re: per-process namespace?

[Ram Pai]

On Tue, 2004-06-29 at 14:10, Mike Waychison wrote:
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> Ram Pai wrote:
> > Is there a way for an application to
> > 1. fork its own namespace and modify it, and
> > 2. still be able to see changes to the system namespace?
> >
> > Al Viro's Per-process namespace implementation provides the first
> > feature.  But is there any work done to do the second part? Is it worth
> > doing?
> >
> > RP
> 
> In what sense?
> 
> The current model has no definition for a 'system namespace'.

by 'system namespace' I mean the very first initial  hand-crafted
namespace. 

> 
> Accessing /proc/<pid>/mounts where <pid> is running in a different
> namespace appears to work.

Are you sure? I dont see it to be the case. I just verified it  on 2.6.7
/proc/<pid>/mounts is a file. However /proc/pid/root is a symbolic link 
to the root directory of the process. So the process with a cloned
namespace wont be able to access it through its namespace.


>   As well, you can always fchdir back into
> another namespace temporarily.  As long as you don't reference any
> file/directories using absolute paths (including following symlinks),
> then you can already navigate the entire namespace.

If this feature is available then great!

> 
> This falls apart though when there are no longer any processes keeping
> that namespace alive.  When this happens, the vfsmount's are unstitched
> and you end up 'stuck' on a given mount :(.

> Another caveat is that the current system disallows you from doing any
> mount/umount's in another namespace (bogus security?)
> .
> 
> - --
> Mike Waychison
> Sun Microsystems, Inc.
> 1 (650) 352-5299 voice
> 1 (416) 202-8336 voice
> http://www.sun.com
> 
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> NOTICE:  The opinions expressed in this email are held by me,
> and may not represent the views of Sun Microsystems, Inc.
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