Date: Sat, 4 Feb 2017 11:57:08 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: "Andrey V. Elsukov" <bu7cher@yandex.ru> Cc: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net>, freebsd-hackers@freebsd.org, Slawa Olhovchenkov <slw@zxy.spb.ru> Subject: Re: How to safely remove rest of GTP? Message-ID: <alpine.BSF.2.20.1702041151110.91330@wonkity.com> In-Reply-To: <515e709a-5c34-0bc1-bc3b-7cff99f6dd97@yandex.ru> References: <201701311543.v0VFh0Bl044986@pdx.rh.CN85.dnsmgr.net> <515e709a-5c34-0bc1-bc3b-7cff99f6dd97@yandex.ru>
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On Tue, 31 Jan 2017, Andrey V. Elsukov wrote: > On 31.01.2017 18:43, Rodney W. Grimes wrote: >> ... much deleted ... >>> >>>> It is impossible to have a corrupted GPT and some >>>> other type of partition table in the same time. >> >> I believe that statement is in error. >> dd if=/boot/boot0 of=/dev/ada0 >> Would not that lead to this very situation if done >> to a GPT parted disk drive? > > 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. > >>> Maybe when only using FreeBSD and gpart, but I'm pretty sure I've seen >>> forum users who have tried some crappy other formatting tool and have >>> overwritten the primary GPT with a valid MBR and left the secondary GPT >>> untouched. This only becomes obvious when they bring the disk back to a >>> FreeBSD system. >> >> As almost all MBR tools are un aware of GPT so well not do anything to >> destroy the secondary GPT, so this is infact very likely to occur. > > Please, give me some working example, when or where you have a problem, and > not some theoretical, based on previous negative experience or memories. I just encountered something similar with a Windows 7 install on a disk that previously had a FreeBSD GPT layout. Clonezilla reported a conflicting GPT/MBR layout on the disk. In gpart, it showed a valid GPT (not corrupt) with no partitions. After all the cursing, I ran 'sudo sgdisk -z /dev/sda' as instructed by Clonezilla. It was only after that I realized I should have saved at least the partition tables.
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