From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762165AbXKPJnk (ORCPT ); Fri, 16 Nov 2007 04:43:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755014AbXKPJnb (ORCPT ); Fri, 16 Nov 2007 04:43:31 -0500 Received: from sacred.ru ([62.205.161.221]:60296 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753618AbXKPJna (ORCPT ); Fri, 16 Nov 2007 04:43:30 -0500 Message-ID: <473D6434.5020201@openvz.org> Date: Fri, 16 Nov 2007 12:34:44 +0300 From: Pavel Emelyanov User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Andrew Morton CC: Cedric Le Goater , Serge Hallyn , "Eric W. Biederman" , Linux Kernel Mailing List , Linux Containers , Theodore Tso Subject: [PATCH][DOCUMENTATION] The namespaces compatibility list doc Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-3.0 (sacred.ru [62.205.161.221]); Fri, 16 Nov 2007 12:34:47 +0300 (MSK) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >>From time to time people begin discussions about how the namespaces are working/going-to-work together. Ted T'so proposed to create some document that describes what problems user may have when he/she creates some new namespace, but keeps others shared. I liked this idea, so here's the initial version of such a document with the problems I currently have in mind and can describe somewhat audibly - the "namespaces compatibility list". The Documentation/namespaces/ directory is about to contain more docs about the namespaces stuff. Thanks to Cedirc for notes and spell checks on the doc. Signed-off-by: Pavel Emelyanov --- commit 83061c56e1c4dcd54d48a62b108d219a7f5279a0 Author: Pavel Date: Fri Nov 16 12:25:53 2007 +0300 Namespaces compatibility list diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX index 910e511..3ead06b 100644 --- a/Documentation/00-INDEX +++ b/Documentation/00-INDEX @@ -262,6 +262,8 @@ mtrr.txt - how to use PPro Memory Type Range Registers to increase performance. mutex-design.txt - info on the generic mutex subsystem. +namespaces/ + - directory with various information about namespaces nbd.txt - info on a TCP implementation of a network block device. netlabel/ diff --git a/Documentation/namespaces/compatibility-list.txt b/Documentation/namespaces/compatibility-list.txt new file mode 100644 index 0000000..9c9e5c1 --- /dev/null +++ b/Documentation/namespaces/compatibility-list.txt @@ -0,0 +1,33 @@ + Namespaces compatibility list + +This document contains the information about the problems user +may have when creating tasks living in different namespaces. + +Here's the summary. This matrix shows the known problems, that +occur when tasks share some namespace (the columns) while living +in different other namespaces (the rows): + + UTS IPC VFS PID User Net +UTS X +IPC X 1 +VFS X +PID 1 1 X +User 2 X +Net X + +1. Both the IPC and the PID namespaces provide IDs to address + object inside the kernel. E.g. semaphore with ipcid or + process group with pid. + + In both cases, tasks shouldn't try exposing this id to some + other task living in a different namespace via a shared filesystem + or IPC shmem/message. The fact is that this ID is only valid + within the namespace it was obtained in and may refer to some + other object in another namespace. + +2. Intentionnaly, two equal user ids in different user namespaces + should not be equal from the VFS point of view. In other + words, user 10 in one user namespace shouldn't have the same + access permissions to files, beloging to user 10 in another + namespace. But currently this is not so. +