[Bug 1835909] [NEW] grub-probe fails to recognize ext4 partition

[Tobias Koch]

Public bug reported:

On a recent Bionic Azure image, the command

    grub-probe --device /dev/sda1 --target=fs_uuid

fails with

    grub-probe: error: not a directory.

The reason for this seems to be that grub-probe finds the minixfs
superblock magic 0x138F at offset

    00000410  8f 13 3a 00 00 00 00 00  02 00 00 00 02 00 00 00
|..:.............|

then assumes it has found a minixfs-formatted partition and exits with
an error when it cannot access it, instead of trying other filesystems
first.

I don't know what the ext filesystem has stored at that position, and
whether it is straight-forward to fabricate this manually.

To reproduce this, you may launch the Azure Bionic image with urn

    Canonical:UbuntuServer:18.04-LTS:18.04.201906271

** Affects: grub2 (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to grub2 in Ubuntu.
https://bugs.launchpad.net/bugs/1835909

Title:
  grub-probe fails to recognize ext4 partition

Status in grub2 package in Ubuntu:
  New

Bug description:
  On a recent Bionic Azure image, the command

      grub-probe --device /dev/sda1 --target=fs_uuid

  fails with

      grub-probe: error: not a directory.

  The reason for this seems to be that grub-probe finds the minixfs
  superblock magic 0x138F at offset

      00000410  8f 13 3a 00 00 00 00 00  02 00 00 00 02 00 00 00
  |..:.............|

  then assumes it has found a minixfs-formatted partition and exits with
  an error when it cannot access it, instead of trying other filesystems
  first.

  I don't know what the ext filesystem has stored at that position, and
  whether it is straight-forward to fabricate this manually.

  To reproduce this, you may launch the Azure Bionic image with urn

      Canonical:UbuntuServer:18.04-LTS:18.04.201906271

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1835909/+subscriptions