linux-ext4 - Re: EXT4 partition changes every time it's mounted. (How to stop this?)

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Message-Id: <A129F9FD-E914-408C-8997-FD145AA2A697@mit.edu>
Date:	Sun, 22 May 2011 07:47:49 -0400
From:	Theodore Tso <tytso@....EDU>
To:	Lee Davis <l.davis37@...il.com>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: EXT4 partition changes every time it's mounted. (How to stop this?)

On May 21, 2011, at 3:45 PM, Lee Davis wrote:

> I'm setting up a Linux system with full disk encryption. I've written a script (to run on every boot) which will verify that neither the MBR or /boot partition (ext4) has been modified.
> 
> Problem is that every time I boot up the system, my /boot partition hashes differently.
> 
> I'm guessing there is something behind the scenes which is changed/updated each time the filesystem is mounted? If so, can it be disabled?

Yes, there is a last mounted time in the superblock.   If you mount the file system read-only, then not only will that field not be changed, but you can guarantee that nothing else will change...

-- Ted

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