apt-get upgrade on Ubuntu 20.04 box fails because there is not enough space in /boot

[evgeni]

Ohai,

I've tested this on the following boxes, but I think others could be affected too:

• generic/ubuntu2004 (libvirt, 4.3.10)
• generic/ubuntu2004 (libvirt, 4.3.12)

When you boot the machine, you see there are at least two kernels installed:

root@ubuntu2004:~# ls /boot/
config-5.4.0-169-generic  grub        initrd.img-5.4.0-169-generic      initrd.img-5.4.0-42-generic      initrd.img.old  System.map-5.4.0-169-generic  vmlinuz                    vmlinuz-5.4.0-42-generic
config-5.4.0-42-generic   initrd.img  initrd.img-5.4.0-169-generic.img  initrd.img-5.4.0-42-generic.img  lost+found      System.map-5.4.0-42-generic   vmlinuz-5.4.0-169-generic  vmlinuz.old

Additionally, the initrds are doubled: initrd.img-5.4.0-169-generic and initrd.img-5.4.0-169-generic.img (and same for -42-). However, the ones ending in .img are not referenced from the grub.cfg at all:

# grep img /boot/grub/grub.cfg 
	initrd	/initrd.img-5.4.0-169-generic
		initrd	/initrd.img-5.4.0-169-generic
		initrd	/initrd.img-5.4.0-169-generic
		initrd	/initrd.img-5.4.0-42-generic
		initrd	/initrd.img-5.4.0-42-generic

Calling apt-get update && apt-get upgrade results in:

Processing triggers for initramfs-tools (0.136ubuntu6.7) ...
update-initramfs: Generating /boot/initrd.img-5.4.0-170-generic
Error 24 : Write error : cannot write compressed block 
E: mkinitramfs failure cpio 141 lz4 -9 -l 24
update-initramfs: failed for /boot/initrd.img-5.4.0-170-generic with 1.
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)

Calling rm -f /boot/*-generic.img before doing the upgrade cleans up enough space to not break things.

I think two optimizations can be made:

• Cleaning those .img files (wherever they come from)
• Shipping the box only with one (latest at build-time) kernel installed