From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Per-instance devpts Date: Fri, 01 Aug 2008 11:12:21 -0700 Message-ID: <48935205.3090807@zytor.com> References: <20080412172933.GA19295@us.ibm.com> <1208027215.28187.17.camel@x61.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1208027215.28187.17.camel-xJGG6ySDJhrj0SQisxZUdA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Eric W. Biederman" Cc: Greg KH , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Containers , Alan Cox , Pavel Emelyanov List-Id: containers.vger.kernel.org Since the issue of PTY namespaces came up (and was rejected) back in April, I have thought a little bit about changing ptys to be tied directly into a devpts instance. devpts would then be a "normal" filesystem, which can be mounted multiple times (or not at all). pty's would then become private to a devpts instance. This is what it would appear would have to change, and I'd like to get people's feeing for the user-space impact: 1. /dev/ptmx would have to change to a symlink, ptmx -> pts/ptmx. 2. Permissions on /dev/ptmx would not be persistent, and would have to be set via devpts mount options (unless they're 0666 root.tty, which would presumably be the default.) 3. The /proc/sys/kernel/pty limit would be global; a per-filesystem limit could be added on top or instead (presumably via a filesystem mount options.) I worry #1 would have substantial user-space impact, but I don't see a way around it, since there would be no obvious way to associate /dev/ptmx with a filesystem. -hpa