linux-kernel - Re: Detecting if you are running in a container

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Message-ID: <20111012150847.GA21061@hallyn.com>
Date:	Wed, 12 Oct 2011 15:08:47 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	david@...g.hm
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Theodore Tso <tytso@....EDU>,
	Matt Helsley <matthltc@...ibm.com>,
	Lennart Poettering <mzxreary@...inter.de>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org, harald@...hat.com, david@...ar.dk,
	greg@...ah.com, Linux Containers <containers@...ts.osdl.org>,
	Linux Containers <lxc-devel@...ts.sourceforge.net>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Paul Menage <paul@...lmenage.org>
Subject: Re: Detecting if you are running in a container

Quoting david@...g.hm (david@...g.hm):
> On Tue, 11 Oct 2011, Eric W. Biederman wrote:
> 
> >david@...g.hm writes:
> >
> >>On Tue, 11 Oct 2011, Eric W. Biederman wrote:
> >>
> >>>Theodore Tso <tytso@....EDU> writes:
> >>>
> >>>>On Oct 11, 2011, at 2:42 AM, Eric W. Biederman wrote:
> >>>>
> >>>I admit for a lot of test cases that it makes sense not to use a full
> >>>set of userspace daemons.  At the same time there is not particularly
> >>>good reason to have a design that doesn't allow you to run a full
> >>>userspace.
> >>
> >>how do you share the display between all the different containers if they are
> >>trying to run the X server?
> >
> >Either X does not start because the hardware it needs is not present or
> >Xnest or similar gets started.
> >
> >>how do you avoid all the containers binding to the same port on the default IP
> >>address?
> >
> >Network namespaces.
> >
> >>how do you arbitrate dbus across the containers.
> >
> >Why should you?
> 
> because the containers are simulating different machines, and dbus
> doesn't work arcross different machines.

Exactly - Eric is saying dbus should not be (and is not) shared among
containers.

> >>when a new USB device gets plugged in, which container gets control of
> >>it?
> >
> >None of them.  Although today they may all get the uevent.  None of the
> >containers should have permission to call mknod to mess with it.
> 
> why would the software inside a container not have the rights to do
> a mknod inside the container?

Why shouldn't an unprivileged user be allowed to mknod on the host?

-serge
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