[bug #36846] Grub 2 hangs on boot after installing on RAID1 device (/dev/md0) but reports no problems during installation

[Iordan]

URL:
  <http://savannah.gnu.org/bugs/?36846>

                 Summary: Grub 2 hangs on boot after installing on RAID1
device (/dev/md0) but reports no problems during installation
                 Project: GNU GRUB
            Submitted by: iiordanov
            Submitted on: Fri 13 Jul 2012 07:55:34 PM GMT
                Category: Installation
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: other
         Reproducibility: Every Time
         Planned Release: None

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Details:

Reproducibility: Always

Steps to reproduce:

0) Zero out the beginning of couple of drives with dd to ensure no previous
grub installation lingers. E.g.:

dd if=/dev/zero of=/dev/sda bs=1024k count=1
dd if=/dev/zero of=/dev/sdb bs=1024k count=1


1) Make a RAID1 device with metadata 0.9 or 1.0. It doesn't matter whether its
degraded (i.e. with one device missing), or not. The resulting device is
/dev/md0.

Since we are creating the RAID array with metadata 0.9 or 1.0, the metadata
ends up at the end of the array, and so the BIOS should have no trouble
reading from each disk individually to load the boot-loader, etc. What's more,
grub2 supports GPT, and ordinarily has no trouble booting from a GPT labeled
disk.


2) Partition said device with GPT, and make a bios partition for Grub2. The
resulting partitions have the form /dev/md0p1, /dev/md0p2, etc.


3) Install Ubuntu 12.04 onto the said RAID1 device. The version of grub that
is installed is 1.99-21ubuntu3.1. We install with FAI, but probably installing
from LiveCD will do just as well.


4) Install Grub2 onto /dev/md0, like this:

grub-install /dev/md0


Expected result:

What we expect at this point is for md to automatically
sync the grub2 changes to both /dev/sda and /dev/sdb, and for the BIOS to be
able to boot from either device.


What happens instead:

What happens instead is that when the BIOS attempts to boot from
either device, it hangs with a cursor blinking at the top-left corner of the
screen *indefinitely*. So, it seems like although Grub 2 thinks the
installation went fine, it is not actually OK.


Notes:

The interesting thing is that when we install Grub 2 to /dev/sda and /dev/sdb
individually, rather than /dev/md0, everything works as intended. I've seen
references on the web indicating that installing to the raw devices is the
right thing to do, but I could not find any official documentation supporting
the claims.

If grub is supposed to be installed to /dev/sda and /dev/sdb, then the bug is
that it doesn't complain when an attempt is made to install it to /dev/md0.

If it should work even when installed to /dev/md0 (with metadata 0.9 and 1.0),
then the bug is that it doesn't actually install properly.

In case it is relevant, here is a print out of the partition table, even
though (as mention previously), Grub 2 does install successfully when the raw
devices are specified (/dev/sda, /dev/sdb):

# parted /dev/md0 print

Model: Linux Software RAID Array (md)
Disk /dev/md0: 500GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number Start End Size File system Name Flags
 1 17.4kB 8389kB 8372kB grub bios_grub
 2 8389kB 21.0GB 21.0GB ext4 root
 3 21.0GB 23.1GB 2097MB linux-swap(v1) swap
 4 23.1GB 33.6GB 10.5GB ext4 var
 5 33.6GB 54.5GB 21.0GB ext4 tmp
 6 54.5GB 75.5GB 21.0GB ext4 local
 7 75.5GB 500GB 425GB ext4 data

Here is a link to the original bug-report on launchpad which contains similar
information to what's in this bug-report;

https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1019389




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