From: Pascal Hambourg <pascal@plouf.fr.eu.org>
To: Wols Lists <antlists@youngman.org.uk>,
David T-G <davidtg-robot@justpickone.org>,
linux-raid@vger.kernel.org
Subject: Re: mirroring existing boot drive sanity check
Date: Fri, 12 Aug 2022 10:38:54 +0200 [thread overview]
Message-ID: <a0143fd9-b99b-6c41-e2a0-da60d0d11cd2@plouf.fr.eu.org> (raw)
In-Reply-To: <fc6cd184-5570-3afa-e477-03008be58183@youngman.org.uk>
Le 12/08/2022 à 09:23, Wols Lists a écrit :
> On 11/08/2022 22:26, Pascal Hambourg wrote:
>> However I do not think it is possible to cleanly boot from an
>> unpartitioned drive used as a software RAID member, as a RAID capable
>> boot loader could hardly fit in the 4-KiB area before the RAID
>> superblock.
>
> Firstly, is there a 4K block there? iirc it's only 1.2 that leaves said
> block.
Yes, but 1.2 is the default, so I assumed it.
> And secondly, does raid assume that 4K space belongs to it? I know it's
> seen as a safety space, so there's nothing permanent left there, but
> that's no guarantee raid doesn't think "that's mine, I'll stash
> something there temporarily". After all, the space allocated explicitly
> begins at the start of the 4K.
On one hand other 1.x subversions do not have that 4-KiB space so I
assume it is not used. Also the gap between the superblock and the data
may be used to hold temporary stuff.
On the other hand ext* filesystems do not use the first sector either
but mke2fs erases it anyway, wiping any existing boot sector.
Anyway, as I wrote previously, no usable boot loader would fit there, so
the point is moot.
prev parent reply other threads:[~2022-08-12 8:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-09 14:50 mirroring existing boot drive sanity check David T-G
2022-08-10 7:03 ` Wols Lists
2022-08-11 21:26 ` Pascal Hambourg
2022-08-12 7:23 ` Wols Lists
2022-08-12 8:38 ` Pascal Hambourg [this message]
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