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Subject: Re: [PATCH 05/10] Core checkpoint/restart support code
From: Nathan Lynch <ntl@pobox.com>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org,
        Oren Laadan <orenl@cs.columbia.edu>,
        Alexey Dobriyan <adobriyan@gmail.com>
In-Reply-To: <20110403190324.GD15044@hallyn.com>
References: <1298936432-29607-1-git-send-email-ntl@pobox.com>
 <1298936432-29607-6-git-send-email-ntl@pobox.com>
 <20110403190324.GD15044@hallyn.com>
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Date: Mon, 04 Apr 2011 10:00:28 -0500
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On Sun, 2011-04-03 at 14:03 -0500, Serge E. Hallyn wrote:
> Quoting ntl@pobox.com (ntl@pobox.com):
> > Only a pid namespace init task - the child process produced by a call
> > to clone(2) with CLONE_NEWPID - is allowed to call these.  The state
> 
> So you make this useful for your cases by only using this with
> application containers - created using lxc-execute, or, more precisely,
> using lxc-init as the container's init.  So a container running a stock
> distro can't be checkpointed.

Correct, a conventional distro init won't work, and application
containers are my focus for now, at least.


> Is this just to keep the patch simple for now, or is there some reason
> to keep this limitation in place?

I guess you're asking whether non-pid-init processes could be allowed to
use the syscalls?  I don't think so... almost certainly not restart(2).

I think that restriction keeps the implementation simple and the
semantics clear.  And init is uniquely positioned to carry out any setup
required (mounts, networking) before calling restart.


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