[Bug 1274320] Re: Error: diskfilter writes are not supported

[Niels Böhm]

I think there is a better "solution" (involving disabling recordfail in
the affected cases, which is LVM for me).

I believe that the correct thing to use to check for LVM or RAID is
grub-probe's "abstraction" target. This returns a list of possible
abstractions below the filesystem level (or an empty string if there are
none). For instance, on a system with just LVM here (hardware RAID is
transparent to the system), it returns that:

    # grub-probe --target=abstraction /boot/
    lvm

On an older system with mdadm RAID1 and boot outside of LVM, it returns
this:

    # grub-probe --target=abstraction /boot
    raid mdraid1x 

    grub-probe --target=abstraction /
    raid mdraid1x lvm 

Also note that older versions of grub-probe output an additional space
at the end of the list if the list is non-empty, so mind that when
parsing the output. There's no such superfluous space on trusty, tho.

So what I do is check the list for possible candidates that would fail
with "recordfail". In my case, this is just "lvm" and I don't have a
system here to test it with md RAID in practice, but I guess you would
just need to extend the "for i in x y z" list with "raid".

The reason while the case statement inside the for loop looks as bit
convoluted is that you could find the culprit at 4 possible places:
making up the whole list, just at the beginning of the list, just at the
end of the list or somewhere in the middle of the list.


** Patch added: "Patch to /etc/grub.d/00_header to account for /boot on LVM"
   https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1274320/+attachment/4293379/+files/grub_00_header.patch

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https://bugs.launchpad.net/bugs/1274320

Title:
  Error: diskfilter writes are not supported

Status in GRand Unified Bootloader:
  Unknown
Status in grub2 package in Ubuntu:
  Triaged
Status in mdadm package in Ubuntu:
  Invalid
Status in grub2 package in Debian:
  New
Status in grub2 package in Fedora:
  Unknown

Bug description:
  Once grub chooses what to boot to, an error shows up and will sit on
  the screen for approx. 5 seconds

  "Error: diskfilter writes are not supported.
  Press any key to continue..."

  From what I understand, this error is related to raid partitions, and
  I have two of them (md0, md1). Both partitions are used (root and
  swap). Raid is assembled with mdadm and are raid0

  This error message started appearing right after grub2 was updated on
  01/27/2014.

  System:    Kernel: 3.13.0-5-generic x86_64 (64 bit) Desktop: KDE 4.11.5 Distro: Ubuntu 14.04 trusty
  Drives:    HDD Total Size: 1064.2GB (10.9% used)
          1: id: /dev/sda model: SanDisk_SDSSDRC0 size: 32.0GB
          2: id: /dev/sdb model: SanDisk_SDSSDRC0 size: 32.0GB
          3: id: /dev/sdc model: ST31000528AS size: 1000.2GB
  RAID:      Device-1: /dev/md1 - active raid: 0 components: online: sdb2 sda3 (swap)       Device-2: /dev/md0 - active raid: 0 components: online: sdb1 sda1 ( / )
  Grub2:    grub-efi-amd64 version 2.02~beta2-5

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: grub-efi-amd64 2.02~beta2-5
  ProcVersionSignature: Ubuntu 3.13.0-5.20-generic 3.13.0
  Uname: Linux 3.13.0-5-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.13.2-0ubuntu2
  Architecture: amd64
  CurrentDesktop: KDE
  Date: Wed Jan 29 17:37:59 2014
  SourcePackage: grub2
  UpgradeStatus: Upgraded to trusty on 2014-01-23 (6 days ago)

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