From owner-freebsd-hackers@freebsd.org  Mon Jan 30 15:55:41 2017
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Date: Mon, 30 Jan 2017 08:55:38 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: "Andrey V. Elsukov" <ae@FreeBSD.org>
cc: Slawa Olhovchenkov <slw@zxy.spb.ru>, freebsd-hackers@freebsd.org
Subject: Re: How to safely remove rest of GTP?
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On Fri, 30 Dec 2016, Andrey V. Elsukov wrote:

> On 30.12.2016 15:44, Slawa Olhovchenkov wrote:
>> How to safely remove rest of GPT?
>> Disk have actual data (part of ZFS), I am don't need to destroy this
>> data.
>> 
>> GEOM: da6: the primary GPT table is corrupt or invalid.
>> GEOM: da6: using the secondary instead -- recovery strongly advised.
>> GEOM: da22: the primary GPT table is corrupt or invalid.
>> GEOM: da22: using the secondary instead -- recovery strongly advised.
>> GEOM: da6: the primary GPT table is corrupt or invalid.
>> GEOM: da6: using the secondary instead -- recovery strongly advised.
>> GEOM: da22: the primary GPT table is corrupt or invalid.
>> GEOM: da22: using the secondary instead -- recovery strongly advised.
>
> You may try attached patch, I did only basic tests, so first try somewhere :)

I really like the idea of gpart being able to remove the secondary GPT, 
but combining it with the existing destroy command is ambiguous.  It's 
hard for the user to tell what will happen, and the command itself 
implies that it will destroy all partitioning.

A different command or option name, maybe, but it's hard to think of a 
good name on a Monday morning. Certainly the problem of stale secondary 
GPTs comes up a lot.