[Bug 1959971] Re: increase /boot partition size

[Michael Mikowski]

Hi Łukasz and Brian: I have been doing quite a bit of research in this
area recently, and also am advocating to get kernel management and
cleanup improved, especially for users who must have separate /boot
partitions. This means professional users who are required to have full
disk encryption according to company IT policies.

Using best practice to manage 3 kernel packages (e.g. oem, lowlatency-
hwe, generic-hwe) results in the need to maintain 6 kernel file sets
(latest and penultimate version for each kernel). Because of the way
kernel cleaning is scheduled, additional space is also required for at
least 2 additional images. You can see the entire reasoning and details
at LP: #1960089.

Our conclusion is that 2.0 GB is the preferred target /boot partition
size for professional systems. This is reinforced by my research which
shows many pros recommend this same size when discussing partitioning
(Just one example: https://adventures-in-
tech.blogspot.com/2018/10/encrypted-ubuntu-installation-with.html)

Given disk space these days, this seems like a small price to pay to
support best practice and (hopefully) a future unattended upgrades
algorithm that honors them as well.

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https://bugs.launchpad.net/bugs/1959971

Title:
  increase /boot partition size

Status in partman-auto package in Ubuntu:
  Triaged
Status in ubiquity package in Ubuntu:
  New
Status in partman-auto source package in Focal:
  Fix Committed
Status in ubiquity source package in Focal:
  New
Status in partman-auto source package in Jammy:
  Triaged
Status in ubiquity source package in Jammy:
  New

Bug description:
  [Impact]
  All new installs of 20.04.

  [Test case]
  1) Install Ubuntu 20.04 on a system
  2) Validate that the size of the /boot partition is greater than or equal to 768MB; should be somewhere between 768MB and 1536GB.

  [Regression potential]
  This may adversely affect installs on tiny disks, by taking up more space for the /boot partition than was previously taken, at the cost of / or /home. As such, failures to install due to insufficient space on a partition, or failure to partition a disk that was previously working should be investigated as possible regressions.
  This is a corner case in general since there is no requirement to allocate a separate partition for /boot in the default configuration, and if you are using a non-default configuration where /boot must be a separate partition, you probably also don't have a disk so small that an additional 256MB of disk usage is a problem.

  ---
  The kernel in Jammy is a bit larger than the one in Focal and our previous /boot partition size calculation (LP: #1716999) likely didn't take into account adding modules like nvidia to the initramfs. Subsequently, we need to revisit the size calculations for Focal.

  I'm utilizing cryptsetup and nvidia modules and have a 164M initrd
  when using lz4 (the default in Focal) compression. Using the same
  formula we previously did we end up with this:

  2* (3*11 + 4*164 + 11) = 1400

  So modifying the maximum size to 1536 seems reasonable, the current
  minimum is 512 which is actually a bit too small for an initrd with
  less modules e.g.:

  2* (3*11 + 4*62 + 11) = 584

  So the minimum should also be increased to 768.

  The default compression level for Jammy is currently being discussed
  and until that is decided we shouldn't make changes to partman-auto
  for Jammy.

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