Re: Challenge: Find potential use cases for non-trivial confinement

[Bas Wijnen]

On Tue, May 02, 2006 at 12:10:18AM +0200, Pierre THIERRY wrote:
> > > For the same reason applied to the faculty or each student, the
> > > program cannot run as an advertised service with CPU quota given
> > > especially by the faculty or taken from the students collectively.
> > This situation needs better system administration, not non-trivial
> > confinement.
> 
> First, stop rejecting answers so fast with so few argumentation. That's
> very annoying. If you know a precise better system administration scheme
> that would fit my requirements for the use case, please expose it.

I can see you are irritated.  I am sorry about this.  I just sent short
answers with things which seemed obviously wrong about the cases.  I may or
may not be correct about that.  I did not intend to suggest "You must be
stupid if you don't see the problem with this use case".  I'm sorry if it
appeared that way.

> And if we accept that better sysadmin is a solution here, it is not an
> ``equivalent, alternative mechanism''.

No, but it would IMO be a case that doesn't need fixing.  If the system
administration is so bad that it cannot respond to wishes from the people
they're supposed to help, then that's a problem that needs solving, but not in
software.  I know this is a real problem, it happens at my own university.
But I don't think it should be solved in the OS.  However, please read on.

> Please keep in mind my mail was an answer to a very specific challenge.
> Please answer only WRT the challenge.

You are correct that the challenge didn't specify that we can assume good
system administration.  Still I don't agree that this criticism was unfounded.

> > These extra requirements are not realistic. The owner of the computer
> > (the faculty) wants things to work. "We cannot touch the quota" is not
> > a valid argument.
> 
> Using external CPU quotas here would be somewhat difficult[1], and
> unfair. You could add a specific quota for the course, and run the
> program as an advertised service on this quota. But if some students use
> the master program more intensively than others, they could harm each
> other. That would introduce a DoS vulnerability.

Now _that_ is a very good argument indeed.  I hadn't thought of this, and need
to think about it a bit more.

Thanks,
Bas

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