[Bug 1959971] Re: [FFE] increase /boot partition size

[Nathan Stratton Treadway]

(In case anyone else finds this bug when trying to track down the
current recommended partition sizes):

I noticed there was another commit on 2022-04-01 for Ubiquity/partman-
auto which referenced this bug:

https://git.launchpad.net/ubiquity/commit/?id=9d1720f9d749885eb13e4bd9e23e5a832219a3ae
  In partman-auto further increase the minimum and maximum sizes for /boot partitions on default, x86, and 
  EFI platforms to a minium of 1792Mb and a maximum of 2048Mb. (LP: #1959971)

A corresponding commit was made to Subiquity on 2022-4-11:

https://github.com/canonical/subiquity/commit/22fa581b66cd76baf7bb8c16b5c4e3ea01c0208f
  boot: further increase suggested sizing: min 1.7G

  Match the change implemented for Ubiquity 22.04.11,
  commit 9d1720f9d749885eb13e4bd9e23e5a832219a3ae.

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

Title:
  [FFE] increase /boot partition size

Status in partman-auto package in Ubuntu:
  Triaged
Status in subiquity package in Ubuntu:
  Fix Released
Status in ubiquity package in Ubuntu:
  Fix Released
Status in partman-auto source package in Focal:
  Fix Released
Status in subiquity source package in Focal:
  Fix Released
Status in ubiquity source package in Focal:
  Fix Released
Status in partman-auto source package in Jammy:
  Triaged
Status in subiquity source package in Jammy:
  Fix Released
Status in ubiquity source package in Jammy:
  Fix Released

Bug description:
  [FFE Discussion]
  Now that changes to the initramfs compression level have been settled for jammy (https://launchpadlibrarian.net/590731434/initramfs-tools_0.140ubuntu12_0.140ubuntu13.diff.gz) we need to update the size of /boot so that the additional size of the initrd is taken into account. This should be done before the Beta as more people may be installing Ubuntu then and we don't want them to have undersized /boot partitions given the problems that this can cause.

  Using the same install of Ubuntu with cryptsetup and nvidia modules my
  initrd is now 188 MB. Plugging that into our formula gets:

  2* (3*11 + 4*188 +11) = 1592

  While that's divisible by two, I think we should bump it a bit more to
  1848.

  [Impact]
  All new installs of 20.04.

  [Test case]
  1) Install Ubuntu 20.04 with encryption (this'll create a separate /boot partition) 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.

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