Efi Stub Warning After Kernel Update
Kernel Update
From time to time, the update manager in Linux Mint will offer you a kernel update.
This is nothing unusual and works exactly the same way as updating installed programs.
Everything else happens automatically in the background; the only difference is that a reboot is required after installing a new kernel.
Warning Message
In 99% of cases, the reboot goes smoothly, and shortly after the Mint logo appears, you’ll see the login screen.
However, from time to time, I get the following warning message during boot:
stub warning failed to measure data for event 1
There are various tips online regarding this, some of which refer to BIOS settings.
Normally, changing the BIOS settings isn’t necessary at all to get rid of the error message—I personally avoid tinkering with the BIOS whenever possible.
Fixing the error message
Warning: Caution is advised when uninstalling kernels, as you’re essentially working at the heart of the system. Therefore, the steps described below are performed at your own risk!
In any case, I would leave the currently active kernel as is.
To do this, open the Linux Mint Update Manager and select the following from the menu:
View → Linux Kernel
Confirm the warning that appears by clicking “Continue.”
For the current version 22 of Linux Mint, as of October 2025, the section listing versions 6.8 is of interest. You’ll likely see a lot of entries there.
Many of the entries are simply marked as “Replaced”—but some still say “Installed.”
Depending on how many new kernels have been installed via the Update Manager since the initial installation, there may be quite a few “Installed” entries.
I’ve been cleaning things up there sporadically—at the latest when I see the warning message mentioned above again during boot.
Normally, I only have the active kernel and 2–3 others installed.
If you clean things up here and leave only 3–4 kernels installed, the warning message should disappear. At least on my computer, there seems to be a direct correlation between the number of installed kernels and the warning message.
The option under “Automation” to automatically remove obsolete kernels doesn’t work on my computer because I don’t have updates set to install automatically—I’ve disabled the top option under “Automation.”
You can find more articles about Linux in this category.
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