CentOS - Aug 2016 - GRUB 2 dumps to grub prompt when installed on >4TB disk

Hi All,

I have a Dell R710 that has 6x1TB in a RAID-5 configuration.  When installing
CentOS 7 using the full disk capacity and booting in UEFI mode the machine dumps
me into a GRUB rescue mode prompt.

  error: disk `,gpt2' not found
  Entering rescue mode...
  grub rescue>

If I use the PERC RAID controller to make the disk smaller ROOTDISK volume of
100GB in size and then a DATA volume of the rest of the disk the system boots
just fine so this seems like a GRUB2 issue.  Any thoughts?

-- 
James A. Peltier
IT Services - Research Computing Group
Simon Fraser University - Burnaby Campus
Phone   : 604-365-6432
Fax     : 778-782-3045
E-Mail  : jpeltier at sfu.ca
Website : http://www.sfu.ca/itservices
Twitter : @sfu_rcg
Powering Engagement Through Technology

On Thu, Aug 18, 2016 at 11:57 AM, James A. Peltier <jpeltier at sfu.ca>
wrote:
> Hi All,
>
> I have a Dell R710 that has 6x1TB in a RAID-5 configuration.

This is hardware RAID 5? Because it's pretty screwy how this ends up
working when using software RAID and might take additional
troubleshooting.


>  When installing CentOS 7 using the full disk capacity and booting in UEFI
mode the machine dumps me into a GRUB rescue mode prompt.
>   error: disk `,gpt2' not found
>   Entering rescue mode...
>   grub rescue>

This is confusing to me because there should be no such thing as grub
rescue on UEFI. On BIOS systems, there is boot.img (formerly stage 1)
and core.img in the MBR gap or on BIOS Boot if GPT disk (formerly
stage 1.5 and stage 2). The core.img is where grub rescue comes from
when it can't find grub modules, in particular normal.mod.

But on UEFI, core.img, normal.mod, and a pile of other modules are all
baked into the grubx64.efi file founds on the EFI system partition.

I suspect two things that can cause normal.mod to not be found:
a. The system is not in fact booting in UEFI mode and there's been
some mistake in the installation of grub.
b. The system is in UEFI mode, but either the installer, or
post-install, grub2-install was run which obliterates the grub2-efi
package installed grubx64.efi, i.e. it's not really proper to run
grub2-install on UEFI systems.

Boot off install media with boot parameter inst.rescue and choose all
the default options; this ought to assemble the file system per fstab,
and you can

chroot /mnt/sysimage
yum reinstall grub2-efi
efibootmgr -v
grep efibootmgr /var/log/anaconda/program.log   ## I think that's
right it might be anaconda.program.log though


It's really just reinstalling grub2-efi that should fix the problem,
the following two options are just information gathering in case the
reboot still doesn't work.

-- 
Chris Murphy

----- Original Message -----
| On Thu, Aug 18, 2016 at 11:57 AM, James A. Peltier <jpeltier at sfu.ca>
wrote:
| > Hi All,
| >
| > I have a Dell R710 that has 6x1TB in a RAID-5 configuration.
| 
| 
| This is hardware RAID 5? Because it's pretty screwy how this ends up
| working when using software RAID and might take additional
| troubleshooting.

Yes, it's a Dell R710XD

| >  When installing CentOS 7 using the full disk capacity and booting in
UEFI
| >  mode the machine dumps me into a GRUB rescue mode prompt.
| >   error: disk `,gpt2' not found
| >   Entering rescue mode...
| >   grub rescue>
| 
| 
| This is confusing to me because there should be no such thing as grub
| rescue on UEFI. On BIOS systems, there is boot.img (formerly stage 1)
| and core.img in the MBR gap or on BIOS Boot if GPT disk (formerly
| stage 1.5 and stage 2). The core.img is where grub rescue comes from
| when it can't find grub modules, in particular normal.mod.
| 
| But on UEFI, core.img, normal.mod, and a pile of other modules are all
| baked into the grubx64.efi file founds on the EFI system partition.
| 
| I suspect two things that can cause normal.mod to not be found:
| a. The system is not in fact booting in UEFI mode and there's been
| some mistake in the installation of grub.
| b. The system is in UEFI mode, but either the installer, or
| post-install, grub2-install was run which obliterates the grub2-efi
| package installed grubx64.efi, i.e. it's not really proper to run
| grub2-install on UEFI systems.

I suspect this is the case.  when attempting to run grub-install the system
claims that the grub2-efi-modules packages aren't installed, so this may be
an installer bug.

| Boot off install media with boot parameter inst.rescue and choose all
| the default options; this ought to assemble the file system per fstab,
| and you can
| 
| chroot /mnt/sysimage
| yum reinstall grub2-efi
| efibootmgr -v
| grep efibootmgr /var/log/anaconda/program.log   ## I think that's
| right it might be anaconda.program.log though
| 
| 
| It's really just reinstalling grub2-efi that should fix the problem,
| the following two options are just information gathering in case the
| reboot still doesn't work.

We'll try this and get back to you soon.

-- 
James A. Peltier
IT Services - Research Computing Group
Simon Fraser University - Burnaby Campus
Phone   : 604-365-6432
Fax     : 778-782-3045
E-Mail  : jpeltier at sfu.ca
Website : http://www.sfu.ca/itservices
Twitter : @sfu_rcg
Powering Engagement Through Technology