Install of 20.10 fails

[Alexander Kallenbach]

Tried to reinstall Ubuntu on my mashine but it fails while trying to install grub.

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: ubiquity 20.10.13
ProcVersionSignature: Ubuntu 5.8.0-25.26-generic 5.8.14
Uname: Linux 5.8.0-25-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu50
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.455
CurrentDesktop: ubuntu:GNOME
Date: Wed Feb 10 22:23:34 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.10 "Groovy Gorilla" - Release amd64 (20201022)
ProcEnviron:
 LANGUAGE=de_DE.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 LC_NUMERIC=C.UTF-8
RebootRequiredPkgs:
 linux-image-5.8.0-43-generic
 linux-base
 linux-image-5.8.0-25-generic
 linux-base
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[P (p92)]

Cause: your /boot is full or too small

grub-install: Fehler: »/usr/lib/grub/x86_64-efi-signed/grubx64.efi.signed« kann nicht nach »/boot/efi/EFI/ubuntu/grubx64.efi« kopiert werden: Auf dem Gerät ist kein Speicherplatz mehr verfügbar.

$ df -h /boot

better keep it no more than 60% full
to make some space you have to uninstall oldest kernel

List installed kernels
# dpkg -l linux-* | grep ^ii

check your current kernel level
# uname -r

Uninstall kernels keeping current one and maybe one level older too
# apt purge linux-image-VERSION-generic linux-modules-VERSION-generic linux-modules-extra-VERSION-generic

with VERSION the kernel versions that you are not currently using (dont remove the one shown by uname -r)

then recheck /boot size

# df -h /boot

then try upgrade