From owner-freebsd-current@FreeBSD.ORG Fri Apr 30 06:54:33 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8247E16A4CE for ; Fri, 30 Apr 2004 06:54:33 -0700 (PDT) Received: from harmony.village.org (rover.bsdimp.com [204.144.255.66]) by mx1.FreeBSD.org (Postfix) with ESMTP id 00D1343D6B for ; Fri, 30 Apr 2004 06:54:33 -0700 (PDT) (envelope-from imp@bsdimp.com) Received: from localhost (warner@rover2.village.org [10.0.0.1]) by harmony.village.org (8.12.10/8.12.9) with ESMTP id i3UDsLZJ090783; Fri, 30 Apr 2004 07:54:21 -0600 (MDT) (envelope-from imp@bsdimp.com) Date: Fri, 30 Apr 2004 07:54:48 -0600 (MDT) Message-Id: <20040430.075448.70646001.imp@bsdimp.com> To: phk@phk.freebsd.dk From: "M. Warner Losh" In-Reply-To: <6695.1083331489@critter.freebsd.dk> References: <20040430.070341.26991317.imp@bsdimp.com> <6695.1083331489@critter.freebsd.dk> X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit cc: freebsd-current@freebsd.org Subject: Re: DEVFS in a chroot? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Apr 2004 13:54:33 -0000 In message: <6695.1083331489@critter.freebsd.dk> "Poul-Henning Kamp" writes: : In message <20040430.070341.26991317.imp@bsdimp.com>, "M. Warner Losh" writes: : >In message: <5473.1083327210@critter.freebsd.dk> : > "Poul-Henning Kamp" writes: : >: >Should I mount /var/chroot/dev as type devfs? : >: : >: Yes: : >: : >: mount -t devfs randomargument /var/chroot/dev : > : >What if I have hundreds of these chroots? We build our product inside : >a chroot right now and I'm worried what the overhead of : >mounting/unmounting this for every build would be... : : As far as I recall, our mountlist handling is not optimised for : hundreds of simultaneous mountpoints: we basically walk the list. : That said, I belive we only do so during the actual mount/unmount : operations, so I do not think there is a performance issue as such. Would the performance issues be mitigated by mounting/unmounting devfs all the time? Eg, only mount it while it is actively being used? Also, the devices that the chroot needs to access are best characterized as simple: null, random, tty. It looks like most of the issues can be delt with, but like you say, there appear to be problems with things like /dev/tty. One alternative would be to tar up /dev and extract it into the chroot. However, this appears to have problems with /dev/tty being wrong for users on other ttys. I've not yet investigated the problems that might accrue with things like ptys and people doing a chroot outside of the build system. Warner