[Pkg-xen-devel] Bug#745419: Bug#745419: xen-utils-4.1: Pygrub fails to boot from LVM LV when something installed in the volume boot record

[Sjors Gielen]

Hi Ian,

Thanks for your reply. My thoughts are inline.

Ian Campbell schreef op 22-04-14 16:14:
> I'm afraid I don't follow your logic here. is_disk_image is trying to
> determine whether or not the device (be it a virtual device or
> otherwise) contains a partition table or not. A device with a partition
> table is a "disk image" as in a "full disk image", as opposed to a
> device which is unpartitioned and could be used via the "per partition
> block device" thing in the block driver.

Ah, that makes sense. So is_disk_image is used to decide whether we're
giving it /dev/sda or /dev/sda1, i.e. there is a partition
table/possibility of multiple partitions, or a single partition that
fills the device. Still, the problem remains there was a single
partition, but it thought there was a partition table.

> It seems that your block device does include the DOS MBR/partition table
> indicator (the 0x55aa signature at the end of the first sector) and
> therefore is considered to be a disk image. But perhaps it doesn't
> actually contain a valid partition table? What does "fdisk -l" report
> for this device?

It would seem so. This was caused by the grub-pc install script; it may
have thought /dev/xvda2 was a disk instead of a partition. `fdisk -l`
seems to indicate a valid but empty list of partitions:

<<<
Disk /dev/vpsdisks/blup.kassala.de-disk: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 cylinders, total 8388608 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: 0x00000000

Device Boot      Start         End      Blocks   Id  System
<<<

Do you think it would be possible for Pygrub to detect this situation
and continue booting from a single-partition image?

> Does this still happen with pygrub from a newer Xen? I can see that much
> has changed around this area since 4.1.x. If you can reproduce with
> something newer then I think your best bet is to report this upstream:
> http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen

I've noticed and investigated this bug on a production Xen machine. At
this moment I have no spare machine to test with later versions of Xen.
Maybe it would be possible for someone else to test this, or I can try
looking through pygrub's history on Xen trunk soon.

Sjors

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 884 bytes
Desc: OpenPGP digital signature
URL: <http://lists.alioth.debian.org/pipermail/pkg-xen-devel/attachments/20140423/1cc1123d/attachment.sig>