[Bug 1928701] [NEW] update-grub does not run on kernel updates

[Bas van der Lei]

Public bug reported:

A fresh Ubuntu 18.04.5 installation (eg. from ubuntu-18.04.5-server-
amd64.iso) on a EFI machine, will not run update-grub when a kernel is
installed or removed. Resulting in an older kernel being booted or
missing/broken entries in grub.cfg.

It seems the following pre/post hook scripts are missing:
    - `/etc/kernel/postinst.d/zz-update-grub`
    - `/etc/kernel/postrm.d/zz-update-grub`

This is due to a version mismatch of grub-efi-amd64 and grub2-common. In
2.04-1ubuntu44 of grub2 these scripts are installed as part of
grub2-common package, while in 2.02-2ubuntu8.23 they are conffiles of
the grub-efi-amd64 (or grub-pc, etc) package.

NOTE: A system that previously had an older version of grub-efi-amd64 or
the grub-pc package installed will not encounter this issue since the
scripts are still present as obsolete conffiles:

```
# dpkg --status grub-efi-amd64
<snip>
Conffiles:
 /etc/kernel/postrm.d/zz-update-grub 536d9d45e3e547638db3c5d58a925b6c obsolete
 /etc/kernel/postinst.d/zz-update-grub 536d9d45e3e547638db3c5d58a925b6c obsolete
```

---

```
$ lsb_release -rd
Description:	Ubuntu 18.04.5 LTS
Release:	18.04

$ apt-cache policy grub-efi-amd64 grub2-common
grub-efi-amd64:
  Installed: 2.04-1ubuntu44
  Candidate: 2.04-1ubuntu44
  Version table:
 *** 2.04-1ubuntu44 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.02-2ubuntu8.17 500
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     2.02-2ubuntu8 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
grub2-common:
  Installed: 2.02-2ubuntu8.23
  Candidate: 2.02-2ubuntu8.23
  Version table:
 *** 2.02-2ubuntu8.23 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.02-2ubuntu8.17 500
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     2.02-2ubuntu8 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
```

---

Could also be the cause of #1922234 and #1927857

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

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https://bugs.launchpad.net/bugs/1928701

Title:
  update-grub does not run on kernel updates

Status in grub2-unsigned package in Ubuntu:
  New

Bug description:
  A fresh Ubuntu 18.04.5 installation (eg. from ubuntu-18.04.5-server-
  amd64.iso) on a EFI machine, will not run update-grub when a kernel is
  installed or removed. Resulting in an older kernel being booted or
  missing/broken entries in grub.cfg.

  It seems the following pre/post hook scripts are missing:
      - `/etc/kernel/postinst.d/zz-update-grub`
      - `/etc/kernel/postrm.d/zz-update-grub`

  This is due to a version mismatch of grub-efi-amd64 and grub2-common.
  In 2.04-1ubuntu44 of grub2 these scripts are installed as part of
  grub2-common package, while in 2.02-2ubuntu8.23 they are conffiles of
  the grub-efi-amd64 (or grub-pc, etc) package.

  NOTE: A system that previously had an older version of grub-efi-amd64
  or the grub-pc package installed will not encounter this issue since
  the scripts are still present as obsolete conffiles:

  ```
  # dpkg --status grub-efi-amd64
  <snip>
  Conffiles:
   /etc/kernel/postrm.d/zz-update-grub 536d9d45e3e547638db3c5d58a925b6c obsolete
   /etc/kernel/postinst.d/zz-update-grub 536d9d45e3e547638db3c5d58a925b6c obsolete
  ```

  ---

  ```
  $ lsb_release -rd
  Description:	Ubuntu 18.04.5 LTS
  Release:	18.04

  $ apt-cache policy grub-efi-amd64 grub2-common
  grub-efi-amd64:
    Installed: 2.04-1ubuntu44
    Candidate: 2.04-1ubuntu44
    Version table:
   *** 2.04-1ubuntu44 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       2.02-2ubuntu8.17 500
          500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
       2.02-2ubuntu8 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
  grub2-common:
    Installed: 2.02-2ubuntu8.23
    Candidate: 2.02-2ubuntu8.23
    Version table:
   *** 2.02-2ubuntu8.23 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       2.02-2ubuntu8.17 500
          500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
       2.02-2ubuntu8 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
  ```

  ---

  Could also be the cause of #1922234 and #1927857

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