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From: Bjoern Steinbrink (bjoern.steinbrink_at_isp4p.net)
Date: Tue 21 Dec 2004 - 18:25:35 GMT


On 2004.12.21 18:19:26 +0100, Ola Lundqvist wrote:
> Hello
>
> I forward this bugreport that I have got from
> Helmut Toplitzer <helmut_at_ifit.uni-klu.ac.at> that fix a problem
> with context misunderstanding at start of a vserver.
>
> It is a quite simple patch and as far as I have tested it works fine.
>
> It is applied to the debian version of util-vserver.
>
> For full information see http://bugs.debian.org/280723
>
> Regards,
>
> // Ola
>
> ----- Forwarded message from Helmut Toplitzer <helmut_at_ifit.uni-klu.ac.at> -----
>
> Envelope-to: ola_at_opal.dhs.org
> Delivery-date: Mon, 15 Nov 2004 16:30:57 +0100
> From: Helmut Toplitzer <helmut_at_ifit.uni-klu.ac.at>
> Organization: University of Klagenfurt
> To: opal_at_debian.org
> Subject: Re: Bug#280723: [util-vserver]: vserver-stat shows wrong server as started one
> Cc: 280723_at_bugs.debian.org
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>
>
> Some analysis:
>
> /usr/sbin/vserver script:
>
> Context of new vserver is set
> - by /etc/vservers/name.conf
> - or by /var/run/vservers/name.ctx
> - or by the chcontext script itself
>
> "running" is evaluated by:
> - /var/run/vservers/name.ctx lockfile exists?
> - (vps ax | grep context | wc -l) >0 ?
>
> 1) Checking for running vserver in "start" makes
> no sense because .ctx files are never deleted
> and it's possible that other vserver has same
> context and is already running.
> So the result of "running" is running even
> if other vserver is started in this context.

What's the sense in having two or more vservers sharing the same
context? It may occur with vserver's having a dynamic context id that a
context id gets reused, but you should use static context ids anyway.
And even if there's another vserver running in the same context, do you
really want a second vserver to be started in that context? I doubt it.
So IMHO checking if the vserver is running before starting it is fine in
the way it is done right now.

>
> 2) Deleting vservers .ctx file makes no sense
> either because it can be missed by a hard reboot,
> kill, etc.
>

And it's not necessary, if no process is actually running in the context
whose id is stored in the .ctx file, the vserver is considered "not
runnning".

> 3) Solution: before starting any vserver test
> for ALL vservers if they are running and remove
> remaining .ctx files of not running ones.
> Once booted into the schema everything should work.
> (hopefully *sigh*)

Now where's the difference, apart from the fact that all outdated .ctx
files are removed? Your patch removes exactly those files that would not
lead to the result that a vserver is considered running...

Regards
Bjoern
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