[ALUG] Unable to install grub to server

steve-ALUG at hst.me.uk steve-ALUG at hst.me.uk
Fri Jun 19 00:17:00 BST 2015

On 17/06/15 20:40, Jenny Hopkins wrote:
> Hi all,
> I'd be grateful for some help getting my server booting again. It's
> running debian jessie, with software RAID and LVM, running xen (or
> was).
> Yesterday one of the disks failed, so I ordered another, and, when it
> arrived today, removed the dead one from the array, put the new disk
> in, and.....landed at the grub rescue prompt.
> So I booted up into a rescue disk, assembled the RAID, mounted the
> root on /mnt, and did a chroot.
> Running install-grub on the disk (/dev/sdb) gave me this error:
> warning: your core.img is unusually large. It won't fit in the embedding area.
> error: embedding is not possible, but this is required for RAID and LVM install.

This seems to explain the message

> So I looked at the partition table.  I have two partitions, /dev/sdb1
> and /dev/sdb2.  The latter is nearly 1TB, and is the root.  Both are
> of type 'linux raid autodetect'.  /dev/sdb1 started at 63, so I
> deleted this partition, created a new one as type linux raid
> autodetect, and it was automatically assigned the start of 2048.
> Then I ran grub install again, calling the raid and ext2 and lvm
> modules, but now I keep getting the error
> grub-install:  error: unknown filesystem
> I'm not entirely sure what I'm actually doing here....been searching
> for help for hours.  I found one page that suggested grub2 gets
> confused by a single disk in an array.
> Here's the current partition table:
> Device     Boot  Start        End    Sectors   Size Id Type
> /dev/sdb1         2048     996029     993982 485.4M fd Linux raid autodetect
> /dev/sdb2  *    996030 1915060454 1914064425 912.7G fd Linux raid autodetect
> /boot is part of the root on /dev/sdb2 rather than a separate lvm one.
> I'm not entirely sure how it even managed to boot before, but I only
> had the /dev/sda2 and /dev/sdb2 in a raid array, so there must have
> been a subtle difference in /dev/sda that had allowed grub to install
> to it.   Maybe grub was installed before I created the RAID array - I
> originally only had one disk in there?
> Anyway, any suggestions very welcome.  The trouble with a xen server
> being that all my eggs are in one proverbial basket.
Bit out of my depth with the rest, but my first thought was how broken 
is the broken disk?  Is it worth looking at the partitions on it and 
working out what their sizes and contents were, then re-creating that on 
the new disk?

Good luck!


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