From: "Helmut Hullen" <Hullen@t-online.de>
To: linux-btrfs@vger.kernel.org
Subject: Re: LABEL only 1 device
Date: 27 Feb 2012 13:24:00 +0100 [thread overview]
Message-ID: <C3f3Dlli1uB@helmut.hullen.de> (raw)
In-Reply-To: <20120227120640.GO1046@twin.jikos.cz>
Hallo, David,
Du meintest am 27.02.12:
[deleting btrfs partition]
>> OK, the real problem you're seeing is that when btrfs removes a
>> device from the filesystem, that device is not modified in any way.
>> This means that the old superblock is left behind on it, containing
>> the FS label information. What you need to do is, immediately after
>> removing a device from the FS, zero the first part of the partition
>> with dd and /dev/zero.
> A correction here: if the device being removed is writable, the
> superblock is cleared so it's not recognized as a part of any other
> fs:
[...]
> Doing this manually means zeroing 4k block at all offsets up to
> partition size:
> Superblock 0 offset 65536
> Superblock 1 offset 67108864
> Superblock 2 offset 274877906944
> Superblock 3 offset 1125899906842624
> Superblock 4 offset 4611686018427387904
My actual experiments:
dd if=/dev/zero of=/dev/sdxn bs=16M count=1
seems to be enough. Perhaps deleting the first 16 MByte is too much.
Viele Gruesse!
Helmut
prev parent reply other threads:[~2012-02-27 12:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-26 15:23 LABEL only 1 device Helmut Hullen
2012-02-26 15:30 ` Hugo Mills
2012-02-26 16:12 ` Helmut Hullen
2012-02-26 16:44 ` Hugo Mills
2012-02-26 16:57 ` Helmut Hullen
2012-02-26 17:14 ` Hugo Mills
2012-02-26 18:11 ` Helmut Hullen
2012-02-27 6:44 ` Helmut Hullen
2012-02-27 10:11 ` Hugo Mills
2012-02-27 10:27 ` Helmut Hullen
2012-02-27 16:48 ` Duncan
2012-02-27 21:15 ` Helmut Hullen
2012-02-27 21:23 ` Hugo Mills
2012-02-27 21:33 ` Felix Blanke
2012-02-27 21:45 ` Hugo Mills
2012-02-27 21:59 ` Helmut Hullen
2012-02-26 18:07 ` Duncan
2012-02-28 22:35 ` Karel Zak
2012-03-01 0:54 ` Duncan
2012-02-27 12:06 ` David Sterba
2012-02-27 12:24 ` Helmut Hullen [this message]
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