From owner-freebsd-questions@FreeBSD.ORG Thu Oct 30 17:49:32 2008 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3490A1065673; Thu, 30 Oct 2008 17:49:32 +0000 (UTC) (envelope-from xcllnt@mac.com) Received: from asmtpout013.mac.com (asmtpout013.mac.com [17.148.16.88]) by mx1.freebsd.org (Postfix) with ESMTP id 1F3308FC1F; Thu, 30 Oct 2008 17:49:31 +0000 (UTC) (envelope-from xcllnt@mac.com) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from [192.168.1.95] (209-128-86-226.bayarea.net [209.128.86.226]) by asmtp013.mac.com (Sun Java(tm) System Messaging Server 6.3-7.03 (built Aug 7 2008; 32bit)) with ESMTPSA id <0K9K00L6A9CI6P50@asmtp013.mac.com>; Thu, 30 Oct 2008 09:48:19 -0700 (PDT) Message-id: <33E2BB19-64F9-42E2-89A6-034051390053@mac.com> From: Marcel Moolenaar To: John Baldwin In-reply-to: <200810300936.05232.jhb@freebsd.org> Date: Thu, 30 Oct 2008 09:48:17 -0700 References: <49059437.4000700@free.fr> <200810291754.07992.jhb@freebsd.org> <200810300936.05232.jhb@freebsd.org> X-Mailer: Apple Mail (2.929.2) Cc: Franck , questions@freebsd.org Subject: Re: GPT Support on Freebsd X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Oct 2008 17:49:32 -0000 On Oct 30, 2008, at 6:36 AM, John Baldwin wrote: > Ok, so it's not a PMBR. My understanding is that a GPT requires the > MBR to be > a PMBR (only one partition in the 4th slot with a special type of > 0xee that > covers the whole disk). What this box is doing is trying to make > the MBR > match the first 4 partitions in the GPT. I'm not sure if you will > be able to > get FreeBSD's GPT stuff to recognize that reliably. Marcel (cc'd) > might have > some ideas. In FreeBSD 6, the kernel checks explicitly for a PMBR when it checks for a GPT. Besides being part of the specification, it also avoids conflicts. In the GEOM framework, there's no a priori support for having one GEOM control another. When there's a valid MBR as well as a valid GPT, it's undeterministic which one will be used, unless they both cooperate. They don't. This is where GPart helps out. In FreeBSD 7 and up, GPart supports multiple partitioning schemes, including MBR and GPT. The kernel will not enforce a PMBR in front of a GPT, because upon detecting both a MBR and a GPT, the GPT will be used. However, this only applies when the kernel is configured with GEOM_PART_MBR and not with GEOM_MBR. At this time GEOM_MBR is still the default. So, to make it work for you, you need at least FreeBSD 7.1 (to be released shortly) or use next month's snapshot and build a custom kernel without GEOM_MBR and with GEOM_PART_MBR. In FreeBSD 8 and up GPart is the default and you won't have to make a custom kernel in that case. FYI, -- Marcel Moolenaar xcllnt@mac.com