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Date: Thu, 29 May 2014 14:36:56 +0400
From: Pavel Emelyanov <xemul@parallels.com>
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To: Richard Weinberger <richard@nod.at>
CC: Vasily Kulikov <segoon@openwall.com>,
        <containers@lists.linux-foundation.org>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v2] /proc/pid/status: show all sets of pid according to
 ns
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On 05/29/2014 02:19 PM, Richard Weinberger wrote:
> Am 29.05.2014 12:02, schrieb Pavel Emelyanov:
>>>> We need to know what pid namespaces a task lives in and how pid, sid and
>>>> pgid look in all of them. A short example with pids only
>>>
>>> So use case is to checkpoint/restore nested containers? :)
>>
>> Yes, but there's one more scenario. AFAIK some applications create pid namespaces 
>> themselves, without starting what is typically called "a container" :) And when 
>> such an applications are run inside, well ... "more real" container (e.g. using
>> openvz, lxc or docker tools) we face this issue.
> 
> Do you know such an application?

There were a couple of them reported on the criu mailing list, but I didn't
track those :(

> I'm a aware of systemd which uses CLONE_NEWNET/NS to implement security features.

Yup, this is its typical behavior.

> We could add a directory like /proc/<pidX>/ns/proc/ which would contain everything
> from /proc/<pidX inside the namespace>/.

But how would it help to find out which $pid directories correspond to which
to properly collect the pid mappings?

> This needs definitely more discussion and must not solved by ad-hoc solutions.

Absolutely.

Thanks,
Pavel