Message-ID: <4FCDD315.502@free.fr>
Date: Tue, 05 Jun 2012 11:36:21 +0200
From: Daniel Lezcano <daniel.lezcano@free.fr>
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To: Glauber Costa <glommer@parallels.com>
CC: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, devel@openvz.org,
        kir@parallels.com, Serge Hallyn <serge.hallyn@canonical.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH] allow a task to join a pid namespace
References: <1338816828-25312-1-git-send-email-glommer@parallels.com>
In-Reply-To: <1338816828-25312-1-git-send-email-glommer@parallels.com>
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On 06/04/2012 03:33 PM, Glauber Costa wrote:
> Currently, it is possible for a process  to join existing
> net, uts and ipc namespaces. This patch allows a process to join an
> existing pid namespace as well.
> 
> For that to remain sane, some restrictions are made in the calling process:
> 
> * It needs to be in the parent namespace of the namespace it wants to jump to
> * It needs to sit in its own session and group as a leader.
> 
> The rationale for that, is that people want to trigger actions in a Container
> from the outside. For instance, mainstream linux recently gained the ability
> to safely reboot a container. It would be desirable, however, that this
> action is triggered from an admin in the outside world, very much like a
> power switch in a physical box.
> 
> This would also allow us to connect a console to the container, provide a
> repair mode for setups without networking (or with a broken one), etc.

Hi Glauber,

I am in favor of this patch but I think the pidns support won't be
complete and some corner-cases are not handled.

May be you can look at Eric's patchset [1] where, IMO, everything is
taken into account. Some of the patches may be already upstream.

Thanks
  -- Daniel

[1]
http://git.kernel.org/?p=linux/kernel/git/ebiederm/linux-namespace-control-devel.git;a=summary
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