This is a tricky one to solve, but doable.
What happened here is that Canonical updated their UEFI Secure Boot signing key and your system's Secure Boot Advanced Targeting variable. In plain terms, they made it so that newer boot files they release are bootable, and older ones aren't. If you got the update and then try to boot an OS that is still using the older files, it won't work and you get a Security Violation error.
Normally the solution here is to update your installation so that you have newer boot files. In this instance, though, you're trying to install from an ISO that has the older boot files. So you can't update the boot files. You have two choices here.
- Disable Secure Boot and leave it that way.
- Disable Secure Boot, boot the 22.04.1 ISO, install, update, and then enable Secure Boot again.
Sadly, both solutions require that you disable Secure Boot at least temporarily. If that's not possible, you will have to install Ubuntu from a sufficiently new ISO. You can install Ubuntu 22.04.2, then install the usual linux-generic kernel and remove the linux-generic-hwe-22.04 kernel. The following instructions describe how.
Warning: Do not follow these instructions on a working system - this is just for reverting to the 5.15 kernel on a new installation of Ubuntu 22.04.2.
To install the older kernel, run sudo apt install linux-generic
- this will automatically pull in everything that makes up the older kernel. However, the newer one will still be installed. To remove it, do sudo apt remove linux-hwe-22.04 && sudo apt autoremove && sudo apt remove linux-image-$(uname -r) linux-headers-$(uname -r) linux-modules-$(uname -r) linux-modules-extra-$(uname -r)
. Note that this assumes that you are currently booted into the HWE kernel. Also, this will uninstall the kernel that you are actively booted into, so make good and sure you installed the other one first!!! The system will display a dire warning when you try to do this - if you installed the older linux-generic kernel already, you can safely go ahead and tell it to remove the kernel anyway.
Once you're done with that, run ls /boot
to make sure that you still actually have a kernel left - if you don't, you forgot to run sudo apt install linux-generic
, in which case you should do that lest your system fail to boot. Once you have a properly installed kernel and the HWE kernel is gone, reboot, then run uname -r
to make sure that you're booted into a 5.15 kernel. If so, you're done, and you should continue to get 5.15 kernel updates normally.