Allow /etc/default/grub overriding via /etc/default/grub.d/

This is related to bug #759545 and bug #1009294. 759545 is about a spurious prompt when /etc/default/grub is unmodified; that bug is probably fixed now and should be closed. Bug #1009294 is about a spurious prompt on cloud images because ucf's cache doesn't reflect the debconf settings used for /etc/default/grub within the image.

Because of this bug, however, the cloud images will continue to carry a delta to /etc/default/grub relative to what's in the grub2 package, and therefore any time there *is* a change to the template, users will continue to get a ucf prompt.

So a solution needs to be found that lets the cloud images override settings without triggering ucf pain.

I'm working on this now. I think it should be /etc/default/grub.d/ rather than /etc/grub.d/, though, as /etc/grub.d/ already has quite specific and different semantics. Directories in /etc/default/ are unusual, but not unprecedented; there are already packages in the archive shipping files in /etc/default/kdm.d/ and /etc/default/lire.d/.

This bug was fixed in the package grub2 - 2.00-7ubuntu1

---------------
grub2 (2.00-7ubuntu1) quantal; urgency=low

  * Resynchronise with Debian. Remaining changes:
    - Adjust for default Ubuntu boot options ("quiet splash").
    - Default to hiding the menu; holding down Shift at boot will show it.
    - Set a monochromatic theme and an appropriate background for Ubuntu.
    - Apply Ubuntu GRUB Legacy changes to legacy update-grub script.
    - Fix backslash-escaping in merge_debconf_into_conf.
    - Remove "GNU/Linux" from default distributor string.
    - Add crashkernel option.
    - Bypass menu unless other OSes are installed or Shift is pressed.
    - Allow Shift to interrupt 'sleep --interruptible'.
    - Reduce visual clutter in normal mode.
    - Remove verbose messages printed before reading configuration.
    - Suppress kernel/initrd progress messages, except in recovery mode.
    - Show the boot menu if the previous boot failed.
    - Adjust upgrade version checks for Ubuntu.
    - Suppress "GRUB loading" message unless Shift is held down.
    - Adjust versions of grub-doc and grub-legacy-doc conflicts.
    - Build-depend on qemu-kvm rather than qemu-system for grub-pc tests.
    - Check hardware support before using gfxpayload=keep.
    - Set vt.handoff=7 for smooth handoff to kernel graphical mode.
    - In recovery mode, add nomodeset to the Linux kernel arguments, and
      remove the 'set gfxpayload=keep' command.
    - Skip Windows os-prober entries on Wubi systems, and suppress the menu
      by default if those are the only other-OS entries.
    - Handle probing striped DM-RAID devices.
    - Replace 'single' by 'recovery' when friendly-recovery is installed.
    - Disable cursor as early as possible in grub_main.
    - Apply patch from Fedora to forbid insmod on UEFI secure boot.
    - Apply patch from Fedora to add a "linuxefi" loader.
    - On amd64, add a raw-uefi custom upload tarball for signing.
  * Fix hwmatch to not override more informative errors from grub_file_open
    with "file not found".
  * Read /etc/default/grub.d/*.cfg after /etc/default/grub (LP: #901600).

grub2 (2.00-7) experimental; urgency=low

  * Backport from upstream:
    - Fix stderr leakage from grub-probe in is_path_readable_by_grub.
    - Fix tftp endianness problem.
  * Merge from Ubuntu:
    - Prefer translations from language packs (LP: #537998). (No-op for
      Debian, but harmless.)
    - Avoid getting confused by inaccessible loop device backing paths
      (LP: #938724).

grub2 (2.00-6) experimental; urgency=low

  [ Colin Watson ]
  * Adjust package descriptions to talk about update-grub, not update-grub2.
  * Backport from upstream:
    - Fix grub-emu build on FreeBSD.
  * Revert gcc-4.6-multilib build-dependency change from 2.00-1, since
    kfreebsd-i386 and hurd-i386 don't have gcc-4.6-multilib. Instead, make
    sure to only install efiemu32.o and efiemu64.o on (linux-)i386,
    kopensolaris-i386, and any-amd64.
  * Manually expand @PACKAGE@ symbols in grub-efi.postinst (closes:
    #688725), grub-linuxbios.postinst (closes: #688726), and grub2.postinst
    (closes: #688724).

  [ Debconf translations ]
  * Lithuanian (R...

Hello Dave, or anyone else affected,

Accepted grub2 into precise-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/grub2/1.99-21ubuntu3.8 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

This seems to be doing the right thing (1.99-21ubuntu3.9).

This bug was fixed in the package grub2 - 1.99-21ubuntu3.9

---------------
grub2 (1.99-21ubuntu3.9) precise; urgency=low

  * Also skip update-grub when running in a container (LP: #1060404).
 -- Colin Watson <email address hidden> Tue, 22 Jan 2013 14:43:32 +0000

This feature looks very useful, but I have not found a shred of
documentation for it. The one aspect I can think of that is
not completely obvious is the order that the grub default files are read.

I did find from reading /usr/sbin/grub-mkconfig
that all of the /etc/default/grub.d files are read in order,
      AFTER the /etc/default/grub file.

I hope that this point is noted when this feature does appear in
the Grub2 docs.

Correction to my comment #7:
   Only files in /etc/default/grub.d that end in '.cfg' are read.
All the more reason documentation is needed.

Same as LenWeisberg, i had to read the source code to find this out (and this save my day, please send it upstream !)