grub on raid1 cannot mount filesystem

[Pavel Lisy]

Hello

I've found strange problem in new Fedora 15. I suppose it should work. 
It's maybe fdisk or grub problem.


Normaly I have this (working) multiboot solution on my home PC:

On first small (100MB) partition are grub1 files only with this config
(grub is installed to MBR): 

--- cut ---
title Fedora 15
   root (hd0,2)
   chainloader +1
title Fedora 14
   root (hd0,4)
   chainloader +1
title Ubuntu
   root (hd0,5)
   chainloader +1
--- cut ---

Grub of linux distributions is installed into their partitions


I want make the same on mirrored environment

2 HD in mirror (raid1):
	size	id	OS/SW		FS
1. part 200MB	fd 	grub		ext4
2. part 8GB	82	SWAP		swap
3. part 10 GB	fd	fedora 15	ext4
4. part extended
5. part 10 GB	fd	fedora 14	ext4
6. part 10 GB	fd	ubuntu		ext4
...
last part rest. of disk - LVM		

I've installed Fedora 15 on
/dev/md0 (/dev/sda1,/dev/sdb1)		/boot
/dev/md1 (/dev/sda3,/dev/sdb3)		/
grub was in MBR and everything worked.
THIS WORKS:
grub> root (hd0,0)
grub> setup (hd0)


When I want put grub of Fedora 15 to start of /dev/sda3 grub is
complaining:

THIS DOESN'T WORK:
grub> root (hd0,2)
grub> setup (hd0,2)
Error 17: cannot mount selected partition

Without mirror (raid1) it works. With raid1 it works only on first
partition. Can you explain me why? 

Thanks in advance

Pavel

[Pavel Lisy]

Bruno Wolff III píše v St 29. 06. 2011 v 16:27 -0500:
>  On Wed, Jun 29, 2011 at 16:18:22 -0500,
>    Bruno Wolff III <bruno(a)wolff.to&gt; wrote:
>  > 
>  > One possible reason is that the raid information may be at the start of
>  > the partition. You want to be using version 0.9 or 1.0. The default version
>  > is 1.2. When installing anaconda gives the /boot partition the appropriate
>  > version when creating the array. You can check the version with mdadm -D .
>  
>  One note on this. The man page info for the -e option is incorrect. -e 1
>  is equivalent to -e 1.2, not -e 1.0 is stated in the man page.
>   
Hello 

You are right

Anaconda in F15 makes mirror for /boot with version 0.9 and others with
1.1. Solution is make mirror yourself (in console with bash) with
version 0.9 or 1.0. Then grub can understand filesystems on it.

Thank you very much

Pavel

[Tom H]

On Wed, Jun 29, 2011 at 5:16 PM, Pavel Lisy <pali(a)tmapy.cz&gt; wrote:
>  I've found strange problem in new Fedora 15. I suppose it should work.
>  It's maybe fdisk or grub problem.
>
>  Normaly I have this (working) multiboot solution on my home PC:
>
>  On first small (100MB) partition are grub1 files only with this config
>  (grub is installed to MBR):
>
>  --- cut ---
>  title Fedora 15
>    root (hd0,2)
>    chainloader +1
>  title Fedora 14
>    root (hd0,4)
>    chainloader +1
>  title Ubuntu
>    root (hd0,5)
>    chainloader +1
>  --- cut ---
>
>  Grub of linux distributions is installed into their partitions
>
>
>  I want make the same on mirrored environment
>
>  2 HD in mirror (raid1):
>         size    id      OS/SW           FS
>  1. part 200MB   fd      grub            ext4
>  2. part 8GB     82      SWAP            swap
>  3. part 10 GB   fd      fedora 15       ext4
>  4. part extended
>  5. part 10 GB   fd      fedora 14       ext4
>  6. part 10 GB   fd      ubuntu          ext4
>  ...
>  last part rest. of disk - LVM
>
>  I've installed Fedora 15 on
>  /dev/md0 (/dev/sda1,/dev/sdb1)          /boot
>  /dev/md1 (/dev/sda3,/dev/sdb3)          /
>  grub was in MBR and everything worked.
>  THIS WORKS:
>  grub> root (hd0,0)
>  grub> setup (hd0)
>
>  When I want put grub of Fedora 15 to start of /dev/sda3 grub is
>  complaining:
>
>  THIS DOESN'T WORK:
>  grub> root (hd0,2)
>  grub> setup (hd0,2)
>  Error 17: cannot mount selected partition
>
>  Without mirror (raid1) it works. With raid1 it works only on first
>  partition. Can you explain me why? 
When you install grub to a partition's boot sector, a list of the
blocks "occupied" by grub's stage1 has to be stored in the first
sector of that partition. Assuming that there's enough space there for
it when you're using mdraid (I suspect that you'd have to ensure that
you're using a metadata version that embeds the metadata elsewhere), I
don't think that you can point at a file through blocks because grub
has no knowledge of mdraid - hence the "cannot mount selected
partition" error.

[Bruno Wolff III]

On Wed, Jun 29, 2011 at 23:16:01 +0200,
  Pavel Lisy <pali(a)tmapy.cz&gt; wrote:
>  
>  THIS DOESN'T WORK:
>  grub> root (hd0,2)
>  grub> setup (hd0,2)
>  Error 17: cannot mount selected partition
>  
>  Without mirror (raid1) it works. With raid1 it works only on first
>  partition. Can you explain me why?  
One possible reason is that the raid information may be at the start of
the partition. You want to be using version 0.9 or 1.0. The default version
is 1.2. When installing anaconda gives the /boot partition the appropriate
version when creating the array. You can check the version with mdadm -D .

[Bruno Wolff III]

On Wed, Jun 29, 2011 at 16:18:22 -0500,
  Bruno Wolff III <bruno(a)wolff.to&gt; wrote:
>  
>  One possible reason is that the raid information may be at the start of
>  the partition. You want to be using version 0.9 or 1.0. The default version
>  is 1.2. When installing anaconda gives the /boot partition the appropriate
>  version when creating the array. You can check the version with mdadm -D . 
One note on this. The man page info for the -e option is incorrect. -e 1
is equivalent to -e 1.2, not -e 1.0 is stated in the man page.