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#1 2012-10-21 22:26:18

Registered: 2011-10-05
Posts: 22

[SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap

Hi guys,

I'm trying to make a fresh install of Archlinux on my laptop but I'm stuck with the bootloader installation.

I chose to give LVM a try and thus need to use GRUB2 because I got used to it over the time and don't want to manage a separate /boot partition.

Everything went ok until I tried to copy the core.img file to the post-MBR gap by issuing grub-install

grub-install --target=i386-pc --recheck /dev/sda

/usr/sbin/grub-bios-setup: warning: your core.img is unusually large.  It won't fit in the embedding area.
/usr/sbin/grub-bios-setup: error: embedding is not possible, but this is required for RAID and LVM install.

So it seems that because of my LVM partitions, GRUB2 needs a bigger core.img ! I didn't know it before starting and I let cfdisk use XP-compliant parition alignment (or whatever it is). Then I created a VG with /dev/sda1 as the only PV in it :

 fdisk -l /dev/sda

Disk /dev/sda: 160.0 GB, 160041885696 bytes, 312581808 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0c1a07c1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *          63   234372284   117186111   8e  Linux LVM
/dev/sda2       234372285   312581807    39104761+  8e  Linux LVM

I took a quick look at the parted documentation but LVM partition resizing is not mentionned :

 Supported file systems:

    ext2, ext3 - restriction: the new start must be the same as the old start.
    fat16, fat32
    reiserfs (if libreiserfs is installed)

But it seems possible to resize virtual partitions using parted ( … html#SEC66) and, by chance, the first virtual partition on my physical partition is my swap partition (which can be resized by parted):

lvdisplay -m

  --- Logical volume ---
  LV Path                /dev/vg1/archSwap
  LV Name                archSwap
  VG Name                vg1
  LV UUID                FCvmH1-7spl-A6N1-AVw9-GPmI-opqX-AP5yVC
  LV Write Access        read/write
  LV Creation host, time , 
  LV Status              available
  # open                 2
  LV Size                3.00 GiB
  Current LE             768
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:3
  --- Segments ---
  Logical extent 0 to 767:
    Type		linear
    Physical volume	/dev/sda1
    Physical extents	0 to 767

So is there any hope I can resize my virtual swap partition using parted then the LVM partition itself (or any other tool capable of it?) or am I screwed up here?

Thanks for your help!

Last edited by sclarckone (2012-10-23 11:30:59)


#2 2012-10-21 22:59:09

From: Cymru
Registered: 2011-11-27
Posts: 6,082

Re: [SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap

How To Ask Questions The Smart Way | Help Vampires

Arch Linux | x86_64 | GPT | EFI boot | refind | stub loader | systemd | LVM2 on LUKS
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#3 2012-10-22 09:05:52

Registered: 2011-10-05
Posts: 22

Re: [SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap

Missed that one! I guess I used cfdisk to partition my disk and it seems that it automatically starts first partition at sector 63 for MBR partitioning scheme... it might worth adding a warning about that in the beginners guide ?

It does seem possible to shrink a  PV ( … -partition) but even in the man pages I don't see any way of specifying where the partitions must start. Besides, I guess that shrinking volumes is done by moving the end so it probably won't work for me.

Since I don't have much to lose and a lot of free space on my PV I'll just try to remove and recreate the physical partition /dev/sda1 and then try to rebuild the lvm using pvchange, vgchange and lvchange.


#4 2012-10-22 10:53:39

From: Indiana, USA
Registered: 2011-10-04
Posts: 765

Re: [SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap


#5 2012-10-23 11:28:56

Registered: 2011-10-05
Posts: 22

Re: [SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap

I couldn't manage to resize the PV...

What I did was removing the physical partition /dev/sda1 then recreate it again starting from sector 2048 instead of 63. But when I tried to rebuild the PV using pvchange it wasn't possible.

It might have been my fault since I didn't check before that the kernel has mapped my previous LV (since I was running from the live environment) and it could be why pvchange was just returning me some error messages (there was something about a cache but I didn't have enough time to look deeper into this).

Anyway, I removed all my partitions, recreated my PV,VG,LV and re-installed Arch. Now it works perfectly.


#6 2012-10-23 12:03:35

Forum Fellow
From: Germany
Registered: 2009-02-17
Posts: 2,281

Re: [SOLVED] LVM/GRUB2 - core.img too big for the post-MBR gap

sclarckone, please do not mark a solved thread CLOSED. This is reserved for threads the moderators put in a read-only state. Use SOLVED instead. See the forum etiquette about this.

(I changed the thread title for you to avoid confusion.)

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