linux-ext4 - Re: hiding an partition and preventing to get automounted

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Date:	Fri, 10 Nov 2006 17:11:57 -0600
From:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
To:	"\"Thomas B." Rücker" <dm8tbr@...npma.org>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: hiding an partition and preventing to get automounted

On Fri, 2006-11-10 at 21:31 +0100, "Thomas B. Rücker" wrote:
> Short description of the situation:
> - embedded linux device running 2.4.19 montavista (Archos PMA430)
> - redesigning the firmware to as open source as possible
> - moved system partition from an loop mounted ext3 image on a fat32
> partition to a real partition.
> - device supports usb-mass-storage mode (complete hdd gets handed over
> to a usb-bridge)
> 
> Now we're trying to avoid unmounting that ext3 partition because we use
> it with unionfs to have a writeable root filesystem.
> The problem is that when the hdd is accessed via usb the operating
> system of that desktop PC might mount that ext3 partition and change it.
> What would be a clean way to hide the partition from systems accessing
> it? What would be a clean way of making it ReadOnly to those systems?
> 
> We had some ideas like using a different magic for the filesystem or a
> high and unique revision number we could patch our kernel for, but I'm
> not sure if there would be bad side effects to that. Marking the
> partition as e.g. hidden FAT16 (0x16) won't keep a linux system from
> recognizing and automounting it.
> 
> Any ideas or pointers?

Using a unique superblock magic sounds simple and is probably as
foolproof as anything.

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center

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