linux-kernel - Re: CGroup Namespaces (v4)

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Date:	Mon, 16 Nov 2015 14:54:52 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Richard Weinberger <richard@....at>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Richard Weinberger <richard.weinberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"open list:ABI/API" <linux-api@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LXC development mailing-list 
	<lxc-devel@...ts.linuxcontainers.org>, Tejun Heo <tj@...nel.org>,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: CGroup Namespaces (v4)

On Mon, Nov 16, 2015 at 09:50:55PM +0100, Richard Weinberger wrote:
> Am 16.11.2015 um 21:46 schrieb Serge E. Hallyn:
> > On Mon, Nov 16, 2015 at 09:41:15PM +0100, Richard Weinberger wrote:
> >> Serge,
> >>
> >> On Mon, Nov 16, 2015 at 8:51 PM,  <serge@...lyn.com> wrote:
> >>> To summarize the semantics:
> >>>
> >>> 1. CLONE_NEWCGROUP re-uses 0x02000000, which was previously CLONE_STOPPED
> >>>
> >>> 2. unsharing a cgroup namespace makes all your current cgroups your new
> >>> cgroup root.
> >>>
> >>> 3. /proc/pid/cgroup always shows cgroup paths relative to the reader's
> >>> cgroup namespce root.  A task outside of  your cgroup looks like
> >>>
> >>>         8:memory:/../../..
> >>>
> >>> 4. when a task mounts a cgroupfs, the cgroup which shows up as root depends
> >>> on the mounting task's  cgroup namespace.
> >>>
> >>> 5. setns to a cgroup namespace switches your cgroup namespace but not
> >>> your cgroups.
> >>>
> >>> With this, using github.com/hallyn/lxc #2015-11-09/cgns (and
> >>> github.com/hallyn/lxcfs #2015-11-10/cgns) we can start a container in a full
> >>> proper cgroup namespace, avoiding either cgmanager or lxcfs cgroup bind mounts.
> >>>
> >>> This is completely backward compatible and will be completely invisible
> >>> to any existing cgroup users (except for those running inside a cgroup
> >>> namespace and looking at /proc/pid/cgroup of tasks outside their
> >>> namespace.)
> >>>    cgroupns-root.
> >>
> >> IIRC one downside of this series was that only the new "sane" cgroup
> >> layout was supported
> >> and hence it was useless for everything which expected the default layout.
> >> Hence, still no systemd for us. :)
> >>
> >> Is this now different?
> > 
> > Yes, all hierachies are no supported.
> > 
> 
> Should read "now"? :-)
> If so, *awesome*!

D'oh!  Yes, now :-)

-serge
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