doc boot issues: raid10 boot device will not boot when degraded; metadata 0.90 is required; bios_grub is required for GPT

Bug #997531 reported by Peter Maloney
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Ubuntu Server Guide
Undecided
Unassigned

Bug Description

https://help.ubuntu.com/12.04/serverguide/advanced-installation.html

The above page is missing three very important details.

1. /boot must be raid1, since it is apparently the only way to successfully boot degraded. I tested raid10, which boots until you pull any disk, and then you get either a black screen, or:
    error: no such disk.
    grub rescue>

So my solution was to have a separate boot raid device that is raid1, while the root system is raid10. Separate raid10s has the same problem (I had them separated already due to the metadata 0.90 not supporting large disks).

2. It should mention that metadata 0.90 is required on the boot raid device (or 1.0 seems to work well on grub 2.x; I didn't test 1.9x). I sure the installer did not do this. And from command line I fixed it by backing up the files, destroying and recreating with:
    mdadm --create -e 0.90 ...

3. With a GPT partition, the installer happily continues without a bios_grub partition, which is very wrong. Manually run, the grub-install command line will produce errors and break the boot, but these don't make it to the installer for the user to see, and the system will still boot until "grub-install" is run. (This is a documentation problem, and also an installer software bug)

My system details:

lsb_release -rd
Description: Ubuntu 12.04 LTS
Release: 12.04

mdadm
3.2.3-2ubuntu1

grub-install
 1.99-21ubuntu3

Linux
3.2.0-23-generic

description: updated
Revision history for this message
Peter Maloney (peter-maloney) wrote :

Minor note about point 3 above:

Unlike what I used for the above message, yesterday I used a netboot to install, and it would warn with a dialog if there was no bios_grub partition (because that option is apparently not supported in kickstart; but it works with preseed). Both were Ubuntu 12.04. My preseed was not created from the "ubuntu-server" default one, so maybe there is just an option in the "ubuntu-server" preseed that is not in my preseed that would suppress this useful warn dialog.

John Kim (kotux)
tags: added: serverguide
John Kim (kotux)
Changed in ubuntu-docs (Ubuntu):
status: New → Invalid
no longer affects: ubuntu-docs (Ubuntu)
description: updated
summary: - doc boot issues: raid10 boot device will not boot when degrade; metadata
- 0.90 is required; bios_grub is required for GPT
+ doc boot issues: raid10 boot device will not boot when degraded;
+ metadata 0.90 is required; bios_grub is required for GPT
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