From owner-freebsd-stable@FreeBSD.ORG Mon May 13 03:14:24 2013 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 4CAFD92F for ; Mon, 13 May 2013 03:14:24 +0000 (UTC) (envelope-from wollman@hergotha.csail.mit.edu) Received: from hergotha.csail.mit.edu (wollman-1-pt.tunnel.tserv4.nyc4.ipv6.he.net [IPv6:2001:470:1f06:ccb::2]) by mx1.freebsd.org (Postfix) with ESMTP id 0867F10B for ; Mon, 13 May 2013 03:14:23 +0000 (UTC) Received: from hergotha.csail.mit.edu (localhost [127.0.0.1]) by hergotha.csail.mit.edu (8.14.5/8.14.5) with ESMTP id r4D3EKQ9016782; Sun, 12 May 2013 23:14:20 -0400 (EDT) (envelope-from wollman@hergotha.csail.mit.edu) Received: (from wollman@localhost) by hergotha.csail.mit.edu (8.14.5/8.14.4/Submit) id r4D3EKaJ016781; Sun, 12 May 2013 23:14:20 -0400 (EDT) (envelope-from wollman) Date: Sun, 12 May 2013 23:14:20 -0400 (EDT) From: Garrett Wollman Message-Id: <201305130314.r4D3EKaJ016781@hergotha.csail.mit.edu> To: jdc@koitsu.org Subject: Re: Reinstalling boot blocks on a ZFS-only system X-Newsgroups: mit.lcs.mail.freebsd-stable In-Reply-To: <20130512205837.GA69605@icarus.home.lan> References: Organization: none X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (hergotha.csail.mit.edu [127.0.0.1]); Sun, 12 May 2013 23:14:20 -0400 (EDT) X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED autolearn=disabled version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on hergotha.csail.mit.edu Cc: freebsd-stable@freebsd.org X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 May 2013 03:14:24 -0000 In article <20130512205837.GA69605@icarus.home.lan>, jdc@koitsu.org writes: >You may also need to set kern.geom.debugflags=0x10 to inhibit GEOM's >"safety measure" / to permit writing to LBA 0; see GEOM(4) and search >for the word "foot". If you have set up your partitioning properly (read: following the clearly recommended best practice on the wiki), there should never, ever be any reason to do this. (That is why it's called a DEBUG flag.) The necessary and sufficient invocation is: # gpart bootcode -b /boot/pmbr -p /boot/gptzfsloader -i 1 [a]daX I have no idea how this works with MBR partitioning, but I would make one suggestion in that regard: DON'T. Whatever makes you think you want to do that, think harder and find another way. -GAWollman