Date: Tue, 04 Oct 2016 10:24:39 -0700 From: John Baldwin <jhb@freebsd.org> To: Warren Block <wblock@wonkity.com> Cc: freebsd-current@freebsd.org, Ngie Cooper <yaneurabeya@gmail.com>, Ernie Luzar <luzar722@gmail.com>, "Hartmann, O." <ohartman@mail.zedat.fu-berlin.de> Subject: Re: Destroy GPT partition scheme absolutely, how? Message-ID: <16661613.eI4FiDRTSB@ralph.baldwin.cx> In-Reply-To: <alpine.BSF.2.20.1610040620250.9819@wonkity.com> References: <20160926150109.0d0d793e@hermann> <1785064.lgVzRW13Wf@ralph.baldwin.cx> <alpine.BSF.2.20.1610040620250.9819@wonkity.com>
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On Tuesday, October 04, 2016 06:23:26 AM Warren Block wrote:
> On Mon, 26 Sep 2016, John Baldwin wrote:
>
> > On Tuesday, September 27, 2016 12:36:22 AM Ngie Cooper wrote:
> >>
> >>> On Sep 26, 2016, at 22:48, Ernie Luzar <luzar722@gmail.com> wrote:
> >>
> >> ...
> >>
> >>> This little script has been posted before. Maybe it will be what your looking for. Called gpart.nuke
> >>>
> >>> #! /bin/sh
> >>> echo "What disk do you want"
> >>> echo "to wipe? For example - da1 :"
> >>> read disk
> >>> echo "OK, in 10 seconds I will destroy all data on $disk!"
> >>> echo "Press CTRL+C to abort!"
> >>> sleep 10
> >>> diskinfo ${disk} | while read disk sectorsize size sectors other
> >>> do
> >>> # Delete MBR and partition table.
> >>> dd if=/dev/zero of=/dev/${disk} bs=${sectorsize} count=1
> >>> # Delete GEOM metadata.
> >>> dd if=/dev/zero of=/dev/${disk} bs=${sectorsize} oseek=`expr $sectors - 2` count=2
> >>> done
> >>
> >> Why not just use "gpart destroy -F provider"?
> >
> > That doesn't always work. In particular, if a disk was partitioned with GPT
> > and then you use normal MBR on it afterwards, the 'gpart destroy -F' of the
> > MBR will leave most of the GPT intact and the disk will come up with the old
> > GPT partitions, not as a raw disk.
>
> Right. So do a gpart destroy -F of whatever is on there, ignoring
> errors, then a gpart create -s gpt. Now there is definitely a secondary
> GPT, and a final gpart destroy -F removes it cleanly.
It is usually simpler to just dd zeroes over the first N and last N sectors.
The only fool-proof way to ensure you don't have dangling tables in the
middle of the disk is to zero the entire disk, but that takes too long.
--
John Baldwin
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