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I am trying to build an Ubuntu desktop machine with RAID array, and am having trouble with the installation of GRUB. The 2 10GB HDDs are partitioned using sgdisk (invoked by a script to ensure identical structures) to create GPT partitions as follows:

1: 1MiB, NOT RAID, unformatted, BIOS-grub flag
2: 200MiB, RAID1, ext2, /boot
3: 2GiB, RAID1, swapfs, (swap)
4: 5GiB, RAID1, ext4, /var
5: 5GiB, RAID1, ext4, /tmp
6: 6GiB, RAID1, ext4, / (root)
7: 22GiB, RAID1, ext4, /usr
8: Remainder, RAID1, ext4, /home

After starting the Live-DVD (either 13.10 or 12.04, they behave identically) and configuring Network address, I install mdadm, and run sudo mdadm --assemble --scan which reports all 7 RAID sets started Ok. In the installation I choose the "Something Else" partitioning option, and distribute the installation as indicated above. At the GRUB installation section I get the response that GRUB cannot install to /dev/sda, and that this is a fatal error. The window offers the options to install to a different drive, continue without installing GRUB, or abort.

I can select any of the options, but the "OK" button never becomes active and thus I cannot proceed. It appears that the installation has crashed, although the System Monitor shows no sign of CPU hogging. However, if I try installing from the Server-CD (which has mdadm included) of 13.10, the installation completes without any problem whatsoever, so the partition setup is clearly RAID-capable with Ubuntu.

Similarly, if I install from the Alternate-DVD then it does so perfectly. But that restricts me to the LTS version, which is not what I want at the moment. (And yes, I'm aware that the next LTS is imminent). Alternatively, if I do NOT combine the /boot partitions as a RAID array but leave them independent, then GRUB installs with no problem. That, of course, leaves me without the protection of the mirror.

I have searched in "AskUbuntu", but have not (yet) been able to find anything that solves my problem. In /dev/mapper there is only "control" (suggestion from Jeff Atwood). Have I perhaps omitted some obscure preliminary action with mdadm? Or is there some other preparatory action I should have performed? Any assistance would be very much appreciated.

Ta Muchly    ClangerMan
My machine is built:
MoBo: Asus M4A89TD PRO/USB3 rev 1.01GX
CPU: AMD Phenom II X4 960T 3.0GHz 8MB 95W Black
RAM: 2x4GiB Kingston Hyper blu KHX1600C9D3B1K2/8GX
Graphics: nVidia NVS 285

Thank you, psusi. Syslog reports as follows (extract of zone of interest):

Apr 16 20:29:56 ubuntu os-prober: debug: /dev/sdb7: part of software raid array
Apr 16 20:29:56 ubuntu os-prober: debug: /dev/sdb8: part of software raid array
Apr 16 20:29:56 ubuntu grub-installer: info: Installing grub on '/dev/sda /dev/sdb'
Apr 16 20:29:56 ubuntu grub-installer: info: grub-install does not support --no-floppy
Apr 16 20:29:56 ubuntu grub-installer: info: Running chroot /target grub-install  --force "/dev/sda"
Apr 16 20:29:56 ubuntu grub-installer: Path `/boot/grub' is not readable by GRUB on boot. Installation is impossible. Aborting.
Apr 16 20:29:56 ubuntu grub-installer: error: Running 'grub-install  --force "/dev/sda"' failed.
Apr 16 20:31:22 ubuntu kernel: [ 2004.531675] usb 1-2.1: new high-speed USB device number 3 using ehci-pci
Apr 16 20:31:22 ubuntu kernel: [ 2004.627008] usb 1-2.1: New USB device found, idVendor=0951, idProduct=1603
Apr 16 20:31:22 ubuntu kernel: [ 2004.627011] usb 1-2.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Apr 16 20:31:22 ubuntu kernel: [ 2004.627013] usb 1-2.1: Product: DataTraveler 2.0000000000000000
Apr 16 20:31:22 ubuntu kernel: [ 2004.627015] usb 1-2.1: Manufacturer: Kingston
Apr 16 20:31:22 ubuntu kernel: [ 2004.627016] usb 1-2.1: SerialNumber: 00000000000000000000219E
Apr 16 20:31:22 ubuntu kernel: [ 2004.627249] usb-storage 1-2.1:1.0: USB Mass Storage device detected
Apr 16 20:31:22 ubuntu kernel: [ 2004.627310] scsi9 : usb-storage 1-2.1:1.0
Apr 16 20:31:23 ubuntu kernel: [ 2005.627426] scsi 9:0:0:0: Direct-Access     Kingston DataTraveler 2.0 1.00 PQ: 0 ANSI: 2

I suspect that the sixth line (/boot/grub not readable) is the significant one. /boot/grub contains two files:

-rw-r--r-- 1 root root  699 Oct 16 20:03 gfxblacklist.txt
-rw-r--r-- 1 root root 1024 Oct 16 21:01 grubenv

The former sounds irrelevant, the latter contains:

# GRUB Environment Block
### (continuous stream of "#" characters to 12.5 lines in the terminal window)

Anyway, I suspect that the /boot/grub being accessed is that of the Live-CD system rather than of the RAID-build, and so inappropriate anyway. Your further advice would be most welcome, and of course if you would like to see further information then do please ask. Thank you so much. C.

marked as duplicate by Eric Carvalho, Panther, waltinator, bain, psusi Jun 17 '14 at 23:35

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • Check /var/log/syslog for more details on the cause of the failure. – psusi Apr 15 '14 at 16:45
  • Try again: extract from syslog report: – ClangerMan Apr 18 '14 at 9:35