From owner-freebsd-hackers@freebsd.org Tue Jan 31 21:08:18 2017 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 75EC2CCA2A0 for ; Tue, 31 Jan 2017 21:08:18 +0000 (UTC) (envelope-from bu7cher@yandex.ru) Received: from forward5h.cmail.yandex.net (forward5h.cmail.yandex.net [IPv6:2a02:6b8:0:f35::15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "forwards.mail.yandex.net", Issuer "Yandex CA" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 307A7373 for ; Tue, 31 Jan 2017 21:08:18 +0000 (UTC) (envelope-from bu7cher@yandex.ru) Received: from smtp2h.mail.yandex.net (smtp2h.mail.yandex.net [IPv6:2a02:6b8:0:f05::116]) by forward5h.cmail.yandex.net (Yandex) with ESMTP id 86E0A20FA8; Wed, 1 Feb 2017 00:08:06 +0300 (MSK) Received: from smtp2h.mail.yandex.net (localhost.localdomain [127.0.0.1]) by smtp2h.mail.yandex.net (Yandex) with ESMTP id 1DD98780BA2; Wed, 1 Feb 2017 00:08:03 +0300 (MSK) Received: by smtp2h.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id 86GpUdRPUH-83j8583S; Wed, 01 Feb 2017 00:08:03 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1485896883; bh=jq7/oix1sKGpZETZvJH1ih3053NZ1ZkPbq7MEuxIyDU=; h=Subject:To:References:Cc:From:Message-ID:Date:In-Reply-To; b=D4MvnuOwsv2P4aVnaMPmcfP9pm/6EWKKh05i2im/zKJR2oQOTtpX6PngwKdh9IxIY T422ZhRXSrprBQedmvg7PfDxqveiMpO78CQaNabtlHK/UGCcGJj/+ftFe26FGIY69k SIkpvu/iRxPYg5vdhISHJDGf2qukb4RQjk9Kl1I0= Authentication-Results: smtp2h.mail.yandex.net; dkim=pass header.i=@yandex.ru X-Yandex-Suid-Status: 1 0,1 0,1 0,1 0 Subject: Re: How to safely remove rest of GTP? To: "Rodney W. Grimes" References: <201701312058.v0VKwlut046163@pdx.rh.CN85.dnsmgr.net> Cc: Warren Block , freebsd-hackers@freebsd.org, Slawa Olhovchenkov From: "Andrey V. Elsukov" Message-ID: Date: Wed, 1 Feb 2017 00:06:47 +0300 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: <201701312058.v0VKwlut046163@pdx.rh.CN85.dnsmgr.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 31 Jan 2017 21:08:18 -0000 On 31.01.2017 23:58, Rodney W. Grimes wrote: >> No, it will not lead to this situation. >> /boot/boot0 is similar to /boot/mbr in the example, and with /dev/ada0 >> all will behaves like with /dev/md0. > > Well if that is the case then the GPT backup copy is... well useless as > I just clobbered the MBR of a drive and now gpart is gona just take that > as fine and dandy? > > Doesnt that defeat the purpose of the backup GPT? When you overwrite PMBR with MBR, you get MBR, but the GPT is still here. If you need to recover your GPT, you need to put PMBR back (or just destroy MBR with `gpart destroy`), and GPT will be detected again. Even if you have overwritten GPT primary header and GPT primary table, backup header and table give a chance for recovery to you. -- WBR, Andrey V. Elsukov