From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753376AbbBKQEA (ORCPT ); Wed, 11 Feb 2015 11:04:00 -0500 Received: from mail-qa0-f41.google.com ([209.85.216.41]:58205 "EHLO mail-qa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752429AbbBKQD7 (ORCPT ); Wed, 11 Feb 2015 11:03:59 -0500 Date: Wed, 11 Feb 2015 11:03:47 -0500 From: Tejun Heo To: "Serge E. Hallyn" Cc: "Eric W. Biederman" , Richard Weinberger , Linux API , Linux Containers , Serge Hallyn , "linux-kernel@vger.kernel.org" , Andy Lutomirski , cgroups mailinglist , Ingo Molnar Subject: Re: [PATCHv3 8/8] cgroup: Add documentation for cgroup namespaces Message-ID: <20150211160347.GE21356@htj.duckdns.org> References: <20150107230615.GA28630@htj.dyndns.org> <87fvbm2nni.fsf@x220.int.ebiederm.org> <87y4peyxw5.fsf@x220.int.ebiederm.org> <20150107233553.GC28630@htj.dyndns.org> <20150211034616.GA25022@mail.hallyn.com> <20150211040957.GC21356@htj.duckdns.org> <20150211042942.GA27931@mail.hallyn.com> <87oap1qbv3.fsf@x220.int.ebiederm.org> <20150211051704.GB24897@mtj.duckdns.org> <20150211160023.GA1579@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150211160023.GA1579@mail.hallyn.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 11, 2015 at 05:00:23PM +0100, Serge E. Hallyn wrote: > We absolutely would love to use cgroup namespaces to run older > userspace in containers. I don't know that it's actually possible > to do both that and use unified hierarchy at the same time though, > which is unfortunate. So an Ubuntu 12.04 container will never, afaics, > be able to run inside an ubuntu 16.04 host that is using unified > hierarchy, without using backported newer versions of lxc (etc) in > the container. So, the constraint there are the controllers. A controller can't be attached to two hierarchies at the same time for obvious reasons, so regardless of NS, you can't use the same controller on a unified hierarchy *and* a traditional hierarchy. NS doesn't adds or substracts from the situation. If you decide to attach a controller to a traditional hierarchy, that's where it's gonna be available. If you attach it to the unified hierarchy, the same story. Thanks. -- tejun