Not enough free disk space for /boot while upgrading from 20.04 LTS to 20.10

[Norbert]

Initially I have a 14.04 LTS system with encrypted LVM default partitioning.
It was successfully upgraded to 16.04 LTS, then to 18.04 LTS and then to 20.04 LTS by using simple do-release-upgrade command.

Now it can't upgrade from 20.04 LTS to 20.10. It complains about the disk space:

```
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done

Calculating the changes

Calculating the changes

Not enough free disk space

The upgrade has aborted. The upgrade needs a total of 206 M free
space on disk '/boot'. Please free at least an additional 89,1 M of
disk space on '/boot'. You can remove old kernels using 'sudo apt
autoremove' and you could also set COMPRESS=xz in
/etc/initramfs-tools/initramfs.conf to reduce the size of your
initramfs.

Restoring original system state

Aborting

```

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.28
ProcVersionSignature: Ubuntu 5.4.0-52.57-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.10
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: MATE
Date: Sun Oct 25 13:27:21 2020
InstallationDate: Installed on 2020-10-24 (0 days ago)
InstallationMedia: Ubuntu MATE 14.04.2 "Trusty Tahr" - LTS amd64 (20150323)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to focal on 2020-10-25 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2020-10-25T13:10:11.116833

[Norbert (nrbrtx)]

Currently I have:

```
$ ls /boot/ --human-readable -lt
total 103M
-rw-r--r-- 1 root root 86M окт 25 12:43 initrd.img-5.4.0-52-generic
drwxr-xr-x 6 root root 1,0K окт 25 12:42 grub
lrwxrwxrwx 1 root root 27 окт 25 11:56 initrd.img.old -> initrd.img-5.4.0-52-generic
lrwxrwxrwx 1 root root 24 окт 25 11:56 vmlinuz.old -> vmlinuz-5.4.0-52-generic
lrwxrwxrwx 1 root root 27 окт 25 02:41 initrd.img -> initrd.img-5.4.0-52-generic
lrwxrwxrwx 1 root root 24 окт 25 02:41 vmlinuz -> vmlinuz-5.4.0-52-generic
drwx------ 2 root root 12K окт 24 16:18 lost+found
-rw------- 1 root root 12M окт 15 13:33 vmlinuz-5.4.0-52-generic
-rw-r--r-- 1 root root 233K окт 15 13:28 config-5.4.0-52-generic
-rw------- 1 root root 4,6M окт 15 13:28 System.map-5.4.0-52-generic
-rw-r--r-- 1 root root 179K авг 18 13:46 memtest86+.bin
-rw-r--r-- 1 root root 181K авг 18 13:46 memtest86+.elf
-rw-r--r-- 1 root root 181K авг 18 13:46 memtest86+_multiboot.bin

$ sudo du -sh /boot/
110M /boot/
```

Setting xz compression:

```
$ cat /etc/initramfs-tools/initramfs.conf | grep COMPRESS
# COMPRESS: [ gzip | bzip2 | lz4 | lzma | lzop | xz ]
COMPRESS=xz
```

does not help either.

Even removal of the all contents of /boot folder does not help:

```
The upgrade has aborted. The upgrade needs a total of 238 M free
space on disk '/boot'. Please free at least an additional 13,5 M of
disk space on '/boot'. You can remove old kernels using 'sudo apt
autoremove' and you could also set COMPRESS=xz in
/etc/initramfs-tools/initramfs.conf to reduce the size of your
initramfs.

```

You have to take such scenarios into account.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[chadwick (mrwick)]

this is exactly the issue during an upgrade of a pine64+. the boot partition was created at 100MB so it is quite impossible to go to 100MB

there is not much there:

 du -sch /boot/*
2.0K /boot/Image.version
3.4M /boot/bat
10K /boot/boot.cmd
10K /boot/boot.scr
3.1M /boot/bootlogo.bmp
338K /boot/font24.sft
350K /boot/font32.sft
1.1M /boot/initrd.img
11M /boot/kernel
4.4M /boot/pine64
2.0K /boot/uEnv.txt
2.0K /boot/uEnv.txt.in
23M total

but there must be a solution to having too small a partition, and if there is not, then an image for pine64+ would be appreciated