From owner-freebsd-questions@freebsd.org Sun Mar 25 04:34:02 2018 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 48574F6C59D for ; Sun, 25 Mar 2018 04:34:02 +0000 (UTC) (envelope-from vas@mpeks.tomsk.su) Received: from relay2.tomsk.ru (mail.sibptus.tomsk.ru [212.73.124.5]) by mx1.freebsd.org (Postfix) with ESMTP id 99CF472CC8 for ; Sun, 25 Mar 2018 04:34:00 +0000 (UTC) (envelope-from vas@mpeks.tomsk.su) X-Virus-Scanned: by clamd daemon 0.98.5_1 for FreeBSD at relay2.tomsk.ru Received: from [212.73.125.240] (HELO admin.sibptus.transneft.ru) by relay2.tomsk.ru (CommuniGate Pro SMTP 5.1.16) with ESMTPS id 39963191; Sun, 25 Mar 2018 10:29:05 +0600 Received: from admin.sibptus.transneft.ru (sudakov@localhost [127.0.0.1]) by admin.sibptus.transneft.ru (8.15.2/8.15.2) with ESMTP id w2P4Xtdj095443; Sun, 25 Mar 2018 11:33:57 +0700 (+07) (envelope-from vas@mpeks.tomsk.su) Received: (from sudakov@localhost) by admin.sibptus.transneft.ru (8.15.2/8.15.2/Submit) id w2P4XpvC095442; Sun, 25 Mar 2018 11:33:51 +0700 (+07) (envelope-from vas@mpeks.tomsk.su) X-Authentication-Warning: admin.sibptus.transneft.ru: sudakov set sender to vas@mpeks.tomsk.su using -f Date: Sun, 25 Mar 2018 11:33:51 +0700 From: Victor Sudakov To: Warren Block Cc: freebsd-questions@freebsd.org Subject: Re: Solved. Re: Dualboot and ZFS Message-ID: <20180325043351.GA95361@admin.sibptus.transneft.ru> References: <20180116034929.GB89443@admin.sibptus.transneft.ru> <20180131082738.GA46395@admin.sibptus.transneft.ru> <547e65d16ef16667f61d88463ca73079@roundcube.fjl.org.uk> <20180319025914.GA57490@admin.sibptus.transneft.ru> <20180322012621.GA15678@admin.sibptus.transneft.ru> <20180323023202.GA55860@admin.sibptus.transneft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: AO "Svyaztransneft", SibPTUS X-PGP-Key: http://www.dreamwidth.org/pubkey?user=victor_sudakov X-PGP-Fingerprint: 10E3 1171 1273 E007 C2E9 3532 0DA4 F259 9B5E C634 User-Agent: Mutt/1.9.3 (2018-01-21) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 Mar 2018 04:34:02 -0000 Warren Block wrote: > On Fri, 23 Mar 2018, Victor Sudakov wrote: > >>>>> > >>>>> sysctl kern.geom.debugflags=0x10 > >>>> > >>>> Please reconsider doing this without it being required. It means "allow > >>>> destroying mounted partitions" and is usually not necessary. > >>> > >>> It is recommended, or even required ("must") by the zfsboot(8) man page: > >> > >> The vagueness here is from the "If the drive is currently in use". It > >> could easily be replaced with "If the user wants to destroy data from a > >> drive that is currently being used". > > > > In my script, the ${DISK} is supposed to be a new disk onto which a > > system is installed (cloned actually), so any data thereon would be > > destroyed anyway. > > > >> I would argue that we should > >> remove or rewrite that, as it is misleading. Overwriting a drive that > >> is "in use" is generally exactly the opposite of what people want. > > > > I'm afraid your concern is a bit misdirected. If you can suggest a way > > to install zfsboot without dd, and document it in zfsboot(8) then of course > > kern.geom.debugflags=0x10 is better avoided. > > That's the thing, dd should work without the debugflags setting. If it > does not, it means you are trying to overwrite something in use. To my surprise, my script works just fine without sysctl kern.geom.debugflags=0x10. This may mean that this requirement in man zfsboot is superfluous. Thanks for pointing this out, I've updated my bug report https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=226714 Still I'm surprised that geom permits my overwriting of a VBR with dd. -- Victor Sudakov, VAS4-RIPE, VAS47-RIPN AS43859