bugGNU GRUB - Bugs: bug #38677, Warning about missing LVM PVs from...

 
 

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bug #38677: Warning about missing LVM PVs from 'grub-probe -t partmap'

Submitted by:  Max Bowsher <maxb>
Submitted on:  Sat 06 Apr 2013 08:39:49 PM UTC  
 
Category: Disk & PartitionSeverity: Major
Priority: 5 - NormalItem Group: Software Error
Status: FixedPrivacy: Public
Assigned to: NoneOriginator Name: 
Open/Closed: ClosedRelease: 
Release: otherReproducibility: Every Time
Planned Release: None

(Jump to the original submission Jump to the original submission)

Wed 10 Apr 2013 08:03:42 PM UTC, comment #7:

Patch attached

(file #27835)

Vladimir Serbinenko <phcoder>
Project Administrator
Wed 10 Apr 2013 03:11:32 PM UTC, comment #6:

I see what happens. When grub asks devmapper which devices are parents of vg0-X it gets only the one which really contains the LV in question but not the other PVs in the same VG. Thinking.

Vladimir Serbinenko <phcoder>
Project Administrator
Sun 07 Apr 2013 07:26:15 PM UTC, comment #5:

In the interests of establishing whether there was any possibility of GRUB being confused by past versions of the VG's metadata, I deactivated the VG (vgchange -an), dd-ed zeros over the first 1MiB of sda1 and sdb1, and re-initialized the LVM metadata from a backup (pvcreate --restorefile, vgcfgrestore).

The problem persists unchanged.

My guesswork following this exercise is that 'grub-probe -t partmap' is only looking at the device it was asked to discover the partmap type of, and then running across a codepath which prints a warning because it didn't discover all PVs in my LVM.

This guesswork is mainly informed by having noticed that running the grub-probe -t partmap for any LV that is located on pv0 complains about not finding pv1, and vice versa.

Max Bowsher <maxb>
Sat 06 Apr 2013 11:14:57 PM UTC, comment #4:

I'm not confident that I could convince GRUB or LVM to operate just on two loop-mounted files independently of the rest of my system. I guess I could build a virtual machine if need be.

Anyway, I'll attach a dump of the first 2MiB of my sda and sdb. The partition starts 1MiB into the disk. The LVM signature is present 512B into the partition, meeting GRUB's requirements.

Max Bowsher <maxb>
Sat 06 Apr 2013 10:59:07 PM UTC, comment #3:

Well GRUB tries to boot even if it meets problems. I meant creating 2 image files, creating msdos partmap on them and then LVM on top of them. GRUB expects to find the LVM signature in first 2048B, aligned to 512B. I need a dump of the beginning which would include the whole LVM metadata, from both disks. Preferably from sdX, so I have partition map as well.

Vladimir Serbinenko <phcoder>
Project Administrator
Sat 06 Apr 2013 10:30:29 PM UTC, comment #2:

Well, by "spurious", I mean that despite the warnings, the system boots just fine.

Could you clarify what you meant by "Can you try recreating it with newly-created images?" ?

Was the specific mention of the first 64K significant? My LVM metadata area appears to be 1MiB in size, and on my sdb1, the active vg definition is beyond the first 64K - could that be part of the problem?

Max Bowsher <maxb>
Sat 06 Apr 2013 09:29:05 PM UTC, comment #1:

The warning is not spurious, if you see it, you really got a problem. GRUB probes for LVM on partitions, just it doesn't report it. Can you try recreating it with newly-created images? Can you attach first 64K of sda1 and sdb1?

Vladimir Serbinenko <phcoder>
Project Administrator
Sat 06 Apr 2013 08:39:49 PM UTC, original submission:

I've been trying to determine why the grub installation process on one of my machines logs seemingly scary warnings:

grub-probe: warning: Couldn't find physical volume `pv1'. Some modules may be missing from core image..

(and the same for pv0)

Upon investigating, the warning is being printed by the command:

grub-probe -d /dev/mapper/vg0-syslv -t partmap

The system setup is a relatively simple one, with two disks, sda and sdb, each of which containing a single whole disk partition which is an LVM PV. The only detail which is slightly interesting is that the partitions start at sector 2048 rather than the traditional sector 63 (I had to move them further into the disk when a GRUB image supporting LVM outgrew 62 sectors).

Some staring at the output of running grub-probe with --verbose suggests that the problem is that it is not considering partitions as worth probing for PVs.

System is running Ubuntu raring with packaged GRUB 2.00-13ubuntu2

Max Bowsher <maxb>

 

Attached Files
file #27835:  use_vgs.diff added by phcoder (3KiB - text/x-diff)
file #27798:  bug38677.tar.bz2 added by maxb (139KiB - application/x-bzip - Dump of 2MiB of sda and sdb)

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by phcoder (Posted a comment)
  • -unavailable- added by maxb (Submitted the item)
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    Follow 5 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 10 Apr 2013 10:09:08 PM UTCphcoderStatusNone=>Fixed
      Open/ClosedOpen=>Closed
    Wed 10 Apr 2013 08:03:42 PM UTCphcoderAttached File-=>Added use_vgs.diff, #27835
    Sat 06 Apr 2013 11:15:51 PM UTCmaxbAttached File-=>Added bug38677.tar.bz2, #27798
    Sat 06 Apr 2013 09:29:05 PM UTCphcoderSummarySpurious warning about missing LVM PVs from \'grub-probe -t partmap\'=>Warning about missing LVM PVs from 'grub-probe -t partmap'

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