Re: Improperly nested partitions, help needed!

[Lennart Sorensen]

On Tue, Sep 21, 2010 at 09:31:16AM +0200, Svante Signell wrote:
> I should have posted to help-grub, but I am not subscribed to that list,
> only grub-devel.
> 
> Can somebody please help me with the following problem:
> (I have asked on Debian lists, and also filed a bug #594158 but no
> response so far).
> 
> When installing a new kernel or a new version of grub I get a warning
> that /dev/sda1 (windows rescue) and /dev/sda3 (linux root /) are 
> improperly nested: /usr/sbin/grub-probe: warn: Discarding improperly nested 
> partition
> (hd1,msdos3,msdos1).
> 
> What does improperly nested mean: overlapping, or something else?
> 
> How to resolve this problem? According to fdisk the sda1 and sda3 partitions 
> are _not_ overlapping:
> Additionally, does the same warning have to be repeated so many times for 
> every kernel entry???

It did not say they overlapped.  It said it found a partition table
inside sda3 which is improper given it is not an extended partition
(sda4 is).

> #> fdisk -l /dev/sda
> 
> Disk /dev/sda: 160.0 GB, 160041885696 bytes
> 240 heads, 63 sectors/track, 20673 cylinders
> Units = cylinders of 15120 * 512 = 7741440 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0xd568d568
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1               1         501     3787528+  1b  Hidden W95 FAT32
> /dev/sda2   *         502       15254   111532680    7  HPFS/NTFS
> /dev/sda3           15255       15512     1950480   83  Linux
> /dev/sda4           15513       20673    39017160    f  W95 Ext'd (LBA)
> /dev/sda5           15513       15930     3160048+  83  Linux
> /dev/sda6           15931       17320    10508368+  83  Linux
> /dev/sda7           17321       20530    24267568+  83  Linux
> /dev/sda8           20531       20673     1081048+  82  Linux swap/Solaris

Is there any chance you used to have an extended partition as sda3 and
then made a linux partition which is now sda3 and your new extended
partition is sda4?

If so, then there is a chance that the first sector of sda3 contains
the old extended partition table, and grub probe might be detecting that.

One way to check would be to do:

dd if=/dev/sda3 of=/tmp/sda3.mbr bs=512 count=1

Then run 'file /tmp/sda3.mbr'.  If it says partition table, then I think
you have found your problem.

If that is what is happening, then it is a question of whether grub-probe
made a mistake when it scanned for partitions in something not marked
as a valid place to look for partitions.  Of course the quick workaround
in that case is to clear that sector (assuming the filesystem doesn't
use the first sector of the partition, which many filesystems avoid
since it is a handy place for boot loaders and such).

If the filesystem does avoid that part of the partition, that would be a
good reason an old extended partition table would have survived creating
a filesystem.

-- 
Len Sorensen