In this short post I'll show you how to resolve the problem when the laptop won't boot unless plugged in on AC power with Linux Mint 20.

The problem can happen for latest versions on Linux Mint and new laptops. Sometimes you may find errors in the logs like:

[ 1.218950] Problem loading UEFI: db X.509 certificate (-65)


Failed to write reg 1a6f4 wait reg 1a706

Usually They are not related to the booting problem. To check more information on them please check:

Linux Mint: Integrity: problem loading X.509 certificate -65 before login

The reason for Linux Mint booting only on AC power is related to power management of Ubuntu.

Note: If you can test your battery - sometimes insufficient battery power can be the culprit.

How to boot Linux Mint on Battery

In order to solve the problem you need to modify the grub boot settings :

  • Open /etc/default/grub with your favorite editor
sudo nano /etc/default/grub
  • Find this line:

and change it to:


Note 1: Sometimes you can try instead of iommu=soft to use:
* dis_ucode_ldr - disable microcode loader - "quiet splash dis_ucode_ldr"
* nomodeset - quiet splash nomodeset

Note 2 - iommu=soft instructs the kernel to use a special implementation to manage memory for applications that can't read above the 4GB limit.

  • Refresh the grub settings by:
sudo update-grub
  • Reboot

Bonus: Save Battery Power On Laptops

If you have problems with battery lifetime or the battery has shorter life in comparison to Windows you can install TLP. TLP is an advanced power management tool for Linux.

It offers multiple power management settings and usually can save minutes and even hours to your battery.

To install TLP on Linux Mint do:

sudo apt install tlp tlp-rdw