linux-kernel - Re: completely hide parts of the partition table from Windows?

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Message-ID: <19083.16290.445891.283072@pilspetsen.it.uu.se>
Date:	Wed, 19 Aug 2009 01:56:18 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	"Andries E. Brouwer" <Andries.Brouwer@....nl>
Cc:	Mikael Pettersson <mikpe@...uu.se>, linux-kernel@...r.kernel.org
Subject: Re: completely hide parts of the partition table from Windows?

Andries E. Brouwer writes:
 > On Tue, Aug 18, 2009 at 11:22:30PM +0200, Mikael Pettersson wrote:
 > 
 > > So what I'm looking for is some sub-partition table format with the
 > > following two properties:
 > > 1. resides in an msdos partition entry of a type that Windows does
 > >    not inspect (for whatever extended partitions or Apple/BSD/Sun
 > >    stuff that Windows may have been taught to recognize)
 > > 2. the locations and sizes of the sub-partitions are NOT limited by
 > >    the parent msdos partition entry
 > 
 > The reason I added type 85 = LINUX_EXTENDED_PARTITION
 > was precisely your concern: it should be something
 > that DOS/Windows doesnt know about.
 > 
 > > I've looked at the code in fs/partitions/msdos.c, and it seems that
 > > most of the extended/BSD/Sun formats don't give me property #2 above.
 > 
 > The standard description of extended partitions says that the size field
 > of the parent extended partition descriptor is irrelevant, only the
 > starting sector matters.
 > 
 > If you look at the parse_extended() code in msdos.c you'll see
 > that it does not use its parameter first_size.
 > (Except in a certain case that you will not be in.)

Right. I misread the "process the data partitions" part to imply
that the limits were enforced for all four entries, not just the
last two usually-junk entries. Thanks for clarifiying that.

 > Make a table that has a Linux extended partition (type 85)
 > that is short enough not to cause Windows to worry. Have logical
 > partitions inside of any size and location you desire.

I have created extended partitions with non-default type
(though not 85). I'll see if I can convince fdisk or parted to
create one with entries exceeding the parent's limits.

Thanks,

/Mikael
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