Increase default /boot size

Describe the bug
/boot is on a separate FS that is 512MB in size. Ubuntu 20.04 itself uses 1GB because the new kernels are too big. This means you will quickly run out of space there and updates will break

To Reproduce
Steps to reproduce the behavior:

Install Elementary 6
Check /boot

Desktop (please complete the following information):

OS: Elementary OS 6 preview

This is now causing AppCenter operating system update failures for a number of people, including me (see linked-to issues, above).

To confirm that you are out of disk space in /boot/:

df -h | grep /boot

Workaround, based on this article, until this is updated in the installer, that worked for me:

(Check the Linux kernel versions you have installed and tweak accordingly. Make sure you leave the latest kernel as well as the one after that that failed to install properly alone. In my case, this was_5.11.0-38-generic_ and 5.11.0-41-generic. I also left 5.11.0-37-generic alone until after 41 installed correctly, out of an abundance of caution.)

sudo rm /boot/*-5.11.0-34*
sudo rm /boot/*-5.11.0-27*
sudo apt install -f

This could also be solved by addressing elementary/switchboard-plug-security-privacy#106

Checked the installed Kernels running dpkg --list 'linux-image*'

un  linux-image                            <none>                <none>       (no description available)
ii  linux-image-5.11.0-40-generic          5.11.0-40.44~20.04.2  amd64        Signed kernel image generic
ii  linux-image-5.11.0-41-generic          5.11.0-41.45~20.04.1  amd64        Signed kernel image generic
ii  linux-image-generic-hwe-20.04          5.11.0.41.45~20.04.19 amd64        Generic Linux kernel image
un  linux-image-unsigned-5.11.0-40-generic <none>                <none>       (no description available)
un  linux-image-unsigned-5.11.0-41-generic <none>                <none>       (no description available)

Which of them can I remove safely? Especially the linux-image-unsigned irritate me and the difference between Signed kernel image generic and Generic Linux kernel image are not clear to me yet.

Thanks for the hint ChildishGiant!

To delete kernels I used Mainline

I agree this is probably a good idea, but the root cause (elementary/triage#91) also needs to be addressed by automatically cleaning up old kernels.

So it looks like you only get the 512MB partition if you're doing encryption:

installer/daemon/Daemon.vala

Line 284 in 2691d62

    
           // 256 MiB is the minimum distinst ESP partition size, so this is 256 MiB in MB plus a bit

I can't confirm ever running out of space without encryption. Can everyone experiencing this issue verify that they are using full disk encryption?

I can confirm that I have enabled LUKS disk encryption by using the installer.

Yep, both the instances I've ran into this I have been using full disk encryption

Ditto on full-disk encryption.

Long-term solution, of course, is to remove older kernels.

Alright, we doubled the size of the boot for encrypted installs, so I'm gonna close this issue. We're still tracking autoremove at elementary/triage#91

The changes are then available for new installations and not for existing installations, right?

@4jNsY6fCVqZv that's correct, we wouldn't be able to change your partitions in an update