From owner-freebsd-stable@FreeBSD.ORG Sun Mar 23 18:42:52 2014 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 246BD492 for ; Sun, 23 Mar 2014 18:42:52 +0000 (UTC) Received: from mail.egr.msu.edu (dauterive.egr.msu.edu [35.9.37.168]) by mx1.freebsd.org (Postfix) with ESMTP id EDEE98B4 for ; Sun, 23 Mar 2014 18:42:50 +0000 (UTC) Received: from dauterive (localhost [127.0.0.1]) by mail.egr.msu.edu (Postfix) with ESMTP id 278EA2A07F for ; Sun, 23 Mar 2014 14:42:44 -0400 (EDT) X-Virus-Scanned: amavisd-new at egr.msu.edu Received: from mail.egr.msu.edu ([127.0.0.1]) by dauterive (dauterive.egr.msu.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id u_5iCrQF4deC for ; Sun, 23 Mar 2014 14:42:44 -0400 (EDT) Received: from EGR authenticated sender Message-ID: <532F2B1B.5090702@egr.msu.edu> Date: Sun, 23 Mar 2014 14:42:35 -0400 From: Adam McDougall User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: freebsd-stable@freebsd.org Subject: Re: ZFS cautions (pool flag additions committed) References: <532F1ED8.8010004@denninger.net> In-Reply-To: <532F1ED8.8010004@denninger.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 23 Mar 2014 18:42:52 -0000 On 03/23/2014 13:50, Karl Denninger wrote: > When ZFS code imports are brought forward that add feature flags there > is a potential time bomb for existing users in that creation of a new > pool becomes non-revertible (except read-only!) with regard to mounting > on older revisions of the code. > > The same thing happens if you do a "zpool upgrade" of course, but at > least that's an explicit act. You might not realize that you're at risk > on a pool create, however, unless you **carefully** scrutinize the flags > that were on the last version compared against the current one. > > The primary "gotcha" here occurs if you don't upgrade your emergency > boot media and for some reason you need to boot from a CD or USB key -- > you can be left SEVERELY screwed, and since -RELEASE is typically not > rebuilt when this happens if you don't have a second machine laying > around on which you can build a RELEASE image.... > > I've caught this twice now since 10.0-RELEASE shipped and, while I > haven't been bit by it, it serves as a caution because eventually > someone tracking -STABLE is going to get badly hurt and be left with an > unrepairable system. IMHO there should be some sort of notice on the > list when new zpool feature flags show up so you're fairly warned that > building a new emergency boot media copy is required if you intend to > track -STABLE on a continuing basis. > I understand your point, but you can also get snapshot isos built pretty regulary, so there should be no need to build your own in an emergency: ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/ISO-IMAGES/ If weekly is not good enough, you can get daily: https://pub.allbsd.org/FreeBSD-snapshots/