2.4TB disk - MBR and GPT coexist?

Jason Thomson jason.thomson at mintel.com
Fri Jan 12 10:11:50 UTC 2007

Jo Rhett wrote:

> Marcel Moolenaar wrote:
>> On Jan 11, 2007, at 1:56 PM, Jo Rhett wrote:
>>> Since we're going to be stuck with old BIOSes for a long time after 
>>> 2TB is a cheap disk drive at [store], is anyone considering doing the 
>>> work to make GPT co-exist with an MBR block?
>> It is already possible for them to coexist. It's not uncommon in the
>> industry to use MBR partitions even though the disk has GPT. The
>> point is that you need to tools to avoid making a mess. Ideally you
>> want the MBR partitions mirrored by the GPT so that the kernel only
>> has to deal with GPT. The BIOS will use the MBR to boot.
>> The gpt(8) tool can actually be used to set this up. You partition
>> the disk with fdisk, but only for the boot partition. Then you run
>> gpt(8) to migrate the MBR into a GPT, specifying the -s option so
>> that you get a single GPT partition overlapping the MBR slice. After
>> that you restore the MBR partition. Now you can use GPT to define
>> a big partition. The kernel will use GPT and since you used -s when
>> you migrate the MBR, the kernel will create device nodes with the
>> same name as it would for the MBR partitions...
> That is exactly what I was hoping to find, but was unable to be certain 
> that it was possible from what I saw in the searches.
> To make this into a step-by-step, what do you mean by "restore the MBR 
> partition" ?  From backup, or...?

Jo, if you manage to do this,  could you possibly post a step-by-step

We want to do this here on an existing box,  with existing data.  (I
know - the safe way is backup & restore - but that's tricky with 1.8TB
of data).

Marcel,  do you know if it is possible to do this without destroying the
existing file systems?

I have a feeling it may be very difficult for us,  because I think we
ended up fudging our set up with two fdisk partitions - one 28G for the
standard filesystems,  and one almost 2T to store data.  The reason why
we want to reconfigure is that we have an additional 250GB we'd like to
be able to access.

I guess we ought to play it safe - but I'd be interested in how you get

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