Re: [PATCH 0/9] namespaces: Introduction

From: Eric W. Biederman
Date: Fri May 19 2006 - 12:28:43 EST

Andrew Morton <akpm@xxxxxxxx> writes:

> Herbert Poetzl <herbert@xxxxxxxxxxxx> wrote:
>> let me
>> give a simple example here:
> Examples are useful.
>> "pid virtualization"
>> - Linux-VServer doesn't really need that right now.
>> we are perfectly fine with "pid isolation" here, we
>> only "virtualize" the init pid to make pstree happy
>> - Snapshot/Restart and Migration will require "full"
>> pid virtualization (that's where Eric and OpenVZ
>> are heading towards)
> snapshot/restart/migration worry me. If they require complete
> serialisation of complex kernel data structures then we have a problem,
> because it means that any time anyone changes such a structure they need to
> update (and test) the serialisation.

There is a strict limit to what is user visible, and if it isn't user visible
we will never need it in a checkpoint. So internal implementation details
should not matter.

> This may be a show-stopper, in which case maybe we only need to virtualise
> pid #1.

Except we do need something for pid isolation, and a pid namespace is
quite possibly the light weight solution. If you can't see the pid it is
clearly isolated from you.

> Anyway. Thanks, guys. It sound like most of this work will be nicely
> separable so we can think about each bit as it comes along.

Yes, and there are enough issues it is significant.

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