Date: Thu, 13 Dec 2001 09:01:56 -0600 (CST)
From: Jesse Pollard <pollard@tomcat.admin.navo.hpc.mil>
Message-Id: <200112131501.JAA41764@tomcat.admin.navo.hpc.mil>
To: bodnar42@phalynx.dhs.org, Stewart Allen <stewart@neuron.com>
Subject: Re: passing params to boot readonly
In-Reply-To: <E16EPYW-0003nW-00@phalynx>
Cc: linux-kernel@vger.kernel.org
Sender: linux-kernel-owner@vger.kernel.org

---------  Received message begins Here  ---------

> 
> On December 12, 2001 21:50, Stewart Allen wrote:
> > I'm in a bit of a pickle and need to find a way to pass boot params to a
> > reiserfs rootfs to *prevent* it from replaying the journal on single-user
> > boot. This may seem like a strange request, but I've got a degraded RAID
> > array that I need to poke around in before deciding whether or not to send
> > a disk off to a rehab lab. If the replay occurs, it will potentially
> > destroy the fs since I'm using a degraded snapshot of the failed disk in
> > hopes of reclaiming *some* of my data. The system is running 2.2.x (can't
> > remember and can't find out w/out booting).
> >
> > Do I have a snowball's chance of pulling this off?
> 
> Well, kinda. The only thing that can deter ReiserFS from replaying the 
> journal is convincing it that the physical media it's on is actually read 
> only. Some quick less/grep work revealed that there is no option that makes 
> the SCSI subsystem claim its devices are readonly (although it'd be extremely 
> useful for situations such as this).
> 
> It'd probably be pretty easy to make a boot disk using a hacked version of 
> ReiserFS that refuses to replay the journal, by adding a "return 0;" near the 
> top of journal_read(struct super_block *) in journal.c. However, you might 
> feel more comfortable sending it off for data recovery than testing kernel 
> hacks on it ;)

Wouldn't it be better to make a backup (dd copy) of the disk volume to another
drive? The raid would not be mounted, so the fs would not be updated.

I would recommend that be done even before sending the disk out.

ALTERNATIVE TO READ-ONLY and this might not be possible.

If the raid is SCSI based, then there is (should be) a read-only switch
in the disk configuration. Most disks do not have a jumper there, and since
they are usually internal only, the option is not used. Putting the jumper
on (or removing one if it is there - depends on the drive) will make the
disk read-only.

Even some IDE drives may have this option, though finding documentation on
it may be difficult to locate.
-------------------------------------------------------------------------
Jesse I Pollard, II
Email: pollard@navo.hpc.mil

Any opinions expressed are solely my own.
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