[debbugs-tracker] bug#36853: closed (mklabel does not clear mdraid version 0.90 metadata)

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Your message dated Tue, 30 Jul 2019 10:29:48 -0700
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and subject line Re: bug#36853: mklabel does not clear mdraid version 0.90 
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has caused the debbugs.gnu.org bug report #36853,
regarding mklabel does not clear mdraid version 0.90 metadata
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36853: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=36853
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--- Begin Message --- Subject: mklabel does not clear mdraid version 0.90 metadata Date: Tue, 30 Jul 2019 21:19:49 +1200

Chasing down a bug report https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1828558 where installing over a device previously used in a RAID array, I found that parted's mklabel does not erase mdraid metadata 0.90 metadata (and only that version). Here's my test script

#!/bin/bash
set -xeu

parted --version
rm -f image.img
truncate -s 1G image.img
n=$(uuidgen | cut -d- -f1)
dev="$(losetup -Pf --show image.img)"
mdadm --create --metadata 0.90 --force --level 1 -n 1 --assume-clean /dev/md/$n $dev
mdadm --stop /dev/md/$n
losetup -d $dev
parted --script --align optimal image.img --  mklabel msdos
wipefs image.img

and here's the output on my system:

+ parted --version
parted (GNU parted) 3.2
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by <http://git.debian.org/?p=parted/parted.git;a=blob_plain;f=AUTHORS>.
+ rm -f image.img
+ truncate -s 1G image.img
++ uuidgen
++ cut -d- -f1
+ n=e0c43267
++ losetup -Pf --show image.img
+ dev=/dev/loop44
+ mdadm --create --metadata 0.90 --force --level 1 -n 1 --assume-clean /dev/md/e0c43267 /dev/loop44
mdadm: array /dev/md/e0c43267 started.
+ mdadm --stop /dev/md/e0c43267
mdadm: stopped /dev/md/e0c43267
+ losetup -d /dev/loop44
+ parted --script --align optimal image.img -- mklabel msdos
+ wipefs image.img
DEVICE    OFFSET     TYPE              UUID                                 LABEL
image.img 0x3fff0000 linux_raid_member 6dbbfe69-809c-7a77-14d5-894fb9296617
image.img 0x1fe      dos                                                    

Looking at ped_disk_clobber none of this is surprising: the 0.90 metadata is somewhere between 127 and 64 kiB from the end of the device and this isn't touched.

If this is indeed deemed a bug it could be pragmatically fixed by wiping more from the end of the disk or more cleverly by using libblkid to locate and zap all superblocks.

Cheers,

mwh

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#36853: mklabel does not clear mdraid version 0.90 metadata
>
>
>
>
> Date: 
>
> Tue, 30 Jul 2019 10:29:48 -0700
>
>
>
>
> User-agent: 
>
> Mutt/1.12.0 (2019-05-25)
>
>
>
>
> On Tue, Jul 30, 2019 at 09:19:49PM +1200, Michael Hudson-Doyle wrote:
> > Chasing down a bug report
> > https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1828558 where
> > installing over a device previously used in a RAID array, I found that
> > parted's mklabel does not erase mdraid metadata 0.90 metadata (and only
> > that version). Here's my test script
>
> This is working as expected, parted tries not to touch more than it
> needs to and this situation will often come up when you re-partition a
> disk using the same values as a previous installation. You need to use
> something like wipefs on the disk before creating the new partitions.
>
> Thanks,
>
> -- 
> Brian C. Lane (PST8PDT) - weldr.io - lorax - parted
>
>
> --- End Message ---