[Bug 1812752] [NEW] UX: changing GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub has no effect in cloud images

[Robie Basak]

Public bug reported:

I need to modify the kernel command line, such as to work around bug
1573095. I edit GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and
rerun update-grub but this has no effect.

The reason is that this is redefined in /etc/default/grub.d/50-cloudimg-
settings.cfg and that one overrides /etc/default/grub. I was misled by
the comment in /etc/default/grub and information widely available on the
Internet that editing /etc/default/grub is sufficient, and looked no
further.

I understand the reason for not modifying /etc/default/grub in cloud
image builds (to avoid future conffile prompts) and I'm not suggesting
that it should be modified. To fix this UX issue properly I think the
grub package needs to provide a mechanism that allows cloud image builds
to override the default without dropping in an overriding file (or for
that override file to be the sole place that users need to look).

This affects grub2 2.02-2ubuntu8.9 from Bionic cloud image build
20190114 for example.

** Affects: cloud-images
     Importance: Undecided
         Status: New

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

** Also affects: grub2 (Ubuntu)
   Importance: Undecided
       Status: New

** Description changed:

  I need to modify the kernel command line, such as to work around bug
- 1573095. I edit /etc/default/grub and rerun update-grub but this has no
- effect.
+ 1573095. I edit GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and
+ rerun update-grub but this has no effect.
  
  The reason is that this is redefined in /etc/default/grub.d/50-cloudimg-
  settings.cfg and that one overrides /etc/default/grub. I was misled by
  the comment in /etc/default/grub and information widely available on the
  Internet that editing /etc/default/grub is sufficient, and looked no
  further.
  
  I understand the reason for not modifying /etc/default/grub in cloud
  image builds (to avoid future conffile prompts) and I'm not suggesting
  that it should be modified. To fix this UX issue properly I think the
  grub package needs to provide a mechanism that allows cloud image builds
  to override the default without dropping in an overriding file.
  
  This affects grub2 2.02-2ubuntu8.9 from Bionic cloud image build
  20190114 for example.

** Description changed:

  I need to modify the kernel command line, such as to work around bug
  1573095. I edit GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and
  rerun update-grub but this has no effect.
  
  The reason is that this is redefined in /etc/default/grub.d/50-cloudimg-
  settings.cfg and that one overrides /etc/default/grub. I was misled by
  the comment in /etc/default/grub and information widely available on the
  Internet that editing /etc/default/grub is sufficient, and looked no
  further.
  
  I understand the reason for not modifying /etc/default/grub in cloud
  image builds (to avoid future conffile prompts) and I'm not suggesting
  that it should be modified. To fix this UX issue properly I think the
  grub package needs to provide a mechanism that allows cloud image builds
- to override the default without dropping in an overriding file.
+ to override the default without dropping in an overriding file (or for
+ that override file to be the sole place that users need to look).
  
  This affects grub2 2.02-2ubuntu8.9 from Bionic cloud image build
  20190114 for example.

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https://bugs.launchpad.net/bugs/1812752

Title:
  UX: changing GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub has no
  effect in cloud images

Status in cloud-images:
  New
Status in grub2 package in Ubuntu:
  New

Bug description:
  I need to modify the kernel command line, such as to work around bug
  1573095. I edit GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and
  rerun update-grub but this has no effect.

  The reason is that this is redefined in /etc/default/grub.d/50
  -cloudimg-settings.cfg and that one overrides /etc/default/grub. I was
  misled by the comment in /etc/default/grub and information widely
  available on the Internet that editing /etc/default/grub is
  sufficient, and looked no further.

  I understand the reason for not modifying /etc/default/grub in cloud
  image builds (to avoid future conffile prompts) and I'm not suggesting
  that it should be modified. To fix this UX issue properly I think the
  grub package needs to provide a mechanism that allows cloud image
  builds to override the default without dropping in an overriding file
  (or for that override file to be the sole place that users need to
  look).

  This affects grub2 2.02-2ubuntu8.9 from Bionic cloud image build
  20190114 for example.

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