From owner-freebsd-hackers Sun Feb 10 8:21:35 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from magellan.palisadesys.com (magellan.palisadesys.com [192.188.162.211]) by hub.freebsd.org (Postfix) with ESMTP id 6D54437B416 for ; Sun, 10 Feb 2002 08:21:32 -0800 (PST) Received: from spencer (desmdslgw5poolb54.desm.uswest.net [63.230.49.54]) (authenticated (0 bits)) by magellan.palisadesys.com (8.11.6/8.11.6) with ESMTP id g1ABKrw19333 (using TLSv1/SSLv3 with cipher RC4-MD5 (128 bits) verified NO); Sun, 10 Feb 2002 05:21:39 -0600 From: "Guy Helmer" To: "'BOUWSMA Beery'" , Subject: RE: nullfs and unionfs Date: Sun, 10 Feb 2002 10:20:44 -0600 Organization: Palisade Systems, Inc Message-ID: <000001c1b24e$ffacea40$0200000a@spencer> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2627 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Importance: Normal In-Reply-To: <200112200108.fBK18fJ00337@crotchety.newsbastards.org> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Wednesday, December 19, 2001 7:09 PM BOUWSMA Beery wrote: > > Is it safe (relatively speaking) to use the null and the union > filesystems? The LINT kernel config file still includes dire > warnings, as do the man pages, but so far I've successfully > mounted a handful of filesystems without panicking my system, > though I've been careful to do it read-only when possible > ... > I do this by keeping the actual source read-write for cvsup > in /usr/local/system, which I then mount_null read-only on > /usr/src. (Likewise ports and stuff) > > Over top of this nullfs /usr/src I mount read-write my own > directory which gets my changes in /usr/local/source-hacks. It looks like there are still some serious problems with this. I just tried a similar thing on FreeBSD 4.4 and 4.5. I created a directory of binaries to use for multiple jails, then null-mounted (read-only) the binaries for each of the jails to use. To allow the /etc and other parts of the jails to be written, I union-mounted a per-jail writeable filesystem over each of the null mounts. It seemed to work well until my jail setup program actually started a binary from inside the jail (i.e., from the null mount) when the kernel panic'ed with trap 12. Guy Helmer Palisade Systems, Inc. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message