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Date:      Wed, 28 Sep 2016 15:02:46 -0400
From:      Allan Jude <allanjude@freebsd.org>
To:        freebsd-current@freebsd.org
Subject:   Re: Destroy GPT partition scheme absolutely, how?
Message-ID:  <9b345002-5fb1-5cc3-3a60-9bf872d79d21@freebsd.org>
In-Reply-To: <CANCZdfpPPOqT0TFhaYiyEvX3hoq%2B=5Jwxdw8xNJ6NTHKRFFAUg@mail.gmail.com>
References:  <20160926150109.0d0d793e@hermann> <57E92726.2020605@gmail.com> <5484D815-4B17-456B-BA60-CC6F4E97AFE3@gmail.com> <1785064.lgVzRW13Wf@ralph.baldwin.cx> <C03C20AC-FE67-4D7C-8239-ED48F844EE38@dons.net.au> <CANCZdfp%2BOq7cYz681zYB%2B1DWqXPgxcKN5kn_YdsgfyDNuQoEOQ@mail.gmail.com> <DDEEDE89-AA72-47E8-9D52-A22A79E6CC2B@dons.net.au> <CANCZdfpPPOqT0TFhaYiyEvX3hoq%2B=5Jwxdw8xNJ6NTHKRFFAUg@mail.gmail.com>

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From: Allan Jude <allanjude@freebsd.org>
To: freebsd-current@freebsd.org
Message-ID: <9b345002-5fb1-5cc3-3a60-9bf872d79d21@freebsd.org>
Subject: Re: Destroy GPT partition scheme absolutely, how?
References: <20160926150109.0d0d793e@hermann> <57E92726.2020605@gmail.com>
 <5484D815-4B17-456B-BA60-CC6F4E97AFE3@gmail.com>
 <1785064.lgVzRW13Wf@ralph.baldwin.cx>
 <C03C20AC-FE67-4D7C-8239-ED48F844EE38@dons.net.au>
 <CANCZdfp+Oq7cYz681zYB+1DWqXPgxcKN5kn_YdsgfyDNuQoEOQ@mail.gmail.com>
 <DDEEDE89-AA72-47E8-9D52-A22A79E6CC2B@dons.net.au>
 <CANCZdfpPPOqT0TFhaYiyEvX3hoq+=5Jwxdw8xNJ6NTHKRFFAUg@mail.gmail.com>
In-Reply-To: <CANCZdfpPPOqT0TFhaYiyEvX3hoq+=5Jwxdw8xNJ6NTHKRFFAUg@mail.gmail.com>

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On 2016-09-27 01:58, Warner Losh wrote:
> On Mon, Sep 26, 2016 at 11:06 PM, O'Connor, Daniel <darius@dons.net.au>=
 wrote:
>>
>>> On 27 Sep 2016, at 14:28, Warner Losh <imp@bsdimp.com> wrote:
>>> dd of 2MB of zeros to the start and end of the disk. That will destro=
y
>>> pretty much everything. For SSDs, sometimes you can do the same with
>>> TRIMs only faster (other times they are slower or unreliable).
>>
>> Yeah, but it would be nicer to not have to know that particular magic =
incarnation :)
>=20
> Disk formatting has always been 3 parts magic, 2 parts luck and 1 part =
skill :)
>=20
> It doesn't fit nicely into geom because metadata can live elsewhere.
>=20
> I forgot to add the caveat not to try this on a disk that is part of a
> RAID volume.
>=20
> Warner
> _______________________________________________
> freebsd-current@freebsd.org mailing list
> https://lists.freebsd.org/mailman/listinfo/freebsd-current
> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.o=
rg"
>=20

I wonder if this issue is related at all to the new 'auto resize' gpart
bits. That leaves the 'uncommitted' transaction pending, and may require
a 'gpart undo' before the other commands will work correctly.

I wonder if something like 'zpool labelclear', but for gpart would be
useful, that just nukes the first and last few MB of the disk. I know in
the installer we jump through a number of hoops to try to clear out old
stuff, and having one command would be better.

--=20
Allan Jude


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