/boot disk partition size

[Michael Mikowski]

Hi Everyone:

Members of the ubuntu-meeting asked me to clarify the issue with /boot. You
can see the bugs filed at https://launchpad.net/bugs/1959971 and
https://launchpad.net/bugs/1960089.
*Personal Background:*
I currently lead the Kubuntu Focus <https://kfocus.org> engineering
efforts, and have been a professional product engineer specializing in
mission-critical HP/HA/HV systems for decades. You can see a overview of my
experience at https://michaelmikowski.com.

*My Assessments:*

*0. This is a low-cost, high-return proposal.* People have pushed back
against increasing the /boot partition, but I find most of the reasoning
does not consider the true impact of a small /boot partition to the
complete product.

*1. The cost to provide the space needed is minimal for almost all FDE
systems. *So why not just do it? Of course, there is more work to be done
for the rest of the product (guide users on kernel selection; improve the
kernel cleaning logic), but this is an important component that is required
in any complete solution. It would provide substantial relief to many users
immediately.

*2. An overfull /boot partition is catastrophic for many users.* Many
cannot recover their system because they don't have a rescue disk or
knowledge of ext4, chroot, LUKS, lvm, cryptesetup, package management, and
more. These people either reload the OS or give up.

*3. This happens frequently, even when everything works as designed*, and
even when just using a single kernel flavor. While on IRC yesterday
discussing this, 3 unsolicited individuals stepped in to comment about how
this is needed. And those are advanced developers who know better. Search
for 'ubuntu full /boot partition' and check out how frequently this
continues to occur.

*4. There are many use cases where multiple kernel flavors will occur*,
such as when the users switches from HWE to OEM to address hardware issues,
or they install lowlatency for studio work. When this happens, the current
size boot partition is highly likely to fill. This can corrupt the system
and require a rescue disk for recovery.

Check out the DFMEA which is used to assess the severity of a failure mode:
https://bugs.launchpad.net/ubuntu/+source/partman-auto/+bug/1959971/comments/7

Finally, I assure you the calculations for kernel boot-file-set sizes (180M
with Nvidia GPU) are correct for 20.04, and will be correct for 22.04
unless the compression technique has been changed. It seems perfectly
reasonable to expect this size to grow to 200M or more over the next 2
years. Also, the headroom + safety factor specified (10 kernel file-sets
total) is reasonable when you consider that systems that reboot less
frequently will accumulate kernels and that a single upgrade can install
multiple additional kernel images.

Sincerely, Mike
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