linux-kernel - Re: Per-instance devpts

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Message-ID: <20080802085443.GA7817@wavehammer.waldi.eu.org>
Date:	Sat, 2 Aug 2008 10:54:43 +0200
From:	Bastian Blank <bastian@...di.eu.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Containers <containers@...ts.osdl.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: Per-instance devpts

On Fri, Aug 01, 2008 at 11:12:21AM -0700, H. Peter Anvin wrote:
> 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.)

On Debian based systems /dev/ptmx is 0666 root.root.  But the gid of tty
is already supplied for devpts.

> 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.

Hmm. Several possibilities:
- Change the filesysteme name and the old name remains usable with
  /dev/ptmx.
  Problem: You could mount the filesystem with the old name within a
  container.
- Make the first mounted one special. 
  Problem: Will not survive a umount/mount cycle. But this would be not
  the case anyway.

But you are sure, none of them is a pretty solution.

Bastian

-- 
I'm a soldier, not a diplomat.  I can only tell the truth.
		-- Kirk, "Errand of Mercy", stardate 3198.9
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