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How To Add a Kernel Boot Parameter in Ubuntu

Ubuntu 20

In this article, we will delve into the process of adding a kernel boot parameter in Ubuntu. Whether you’re looking to debug an issue or simply want to modify your system’s behavior, this guide will provide you with a step-by-step approach.

Quick Answer

To add a kernel boot parameter in Ubuntu, you can do it temporarily by editing the kernel line in the GRUB bootloader during system startup. For a permanent addition, you need to modify the GRUB bootloader file and update its configuration.

What is a Kernel Boot Parameter?

Kernel boot parameters are used to instruct the kernel about the hardware components of the system, the modules to load, or the system behaviors to adopt. They are typically added to the end of the Linux kernel line in the GRUB bootloader file.

Temporary Addition of Kernel Boot Parameter

Adding a kernel boot parameter temporarily is useful for testing purposes. Here’s how to do it:

  1. Start your system and wait for the GRUB menu to show up. If you don’t see it, press and hold the left Shift key right after starting the system. In UEFI mode, you may need to press Esc repeatedly.
  2. Highlight the kernel you want to use and press the e key. This action allows you to edit the commands associated with the highlighted kernel.
  3. Locate the line starting with linux and navigate to its end.
  4. Add the boot parameter foo=bar to the end of the line. Here, foo=bar is an example parameter. Replace it with the parameter you want to add.
  5. Boot with the added parameter by pressing Ctrl + x.

Permanent Addition of Kernel Boot Parameter

If the testing is successful and you want to make the kernel boot parameter permanent, follow these steps:

  1. Open a terminal or press Alt + F2 to run a command.
  2. Run the command sudo nano /etc/default/grub and enter your password when prompted. This command opens the GRUB bootloader file in a text editor with root permissions.
  3. Find the line starting with GRUB_CMDLINE_LINUX_DEFAULT and append foo=bar to its end. For example: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash foo=bar". This line is where Ubuntu defines the default kernel boot parameters.
  4. Save the file and close the editor. If you’re using nano, you can do this by pressing Ctrl + x, then y to confirm saving changes, and Enter to confirm the file name.
  5. Update GRUB’s configuration file by running sudo update-grub in the terminal. This command makes sure that the changes you made are written to the main GRUB bootloader file.
  6. Reboot your system. On the next reboot, the kernel will be started with the added boot parameter.

To remove the parameter permanently, simply remove it from GRUB_CMDLINE_LINUX_DEFAULT in the /etc/default/grub file and run sudo update-grub again.

Verifying the Changes

To verify that the kernel boot parameter has been added successfully, you can execute cat /proc/cmdline in a terminal. This command displays the parameters your kernel booted with.


Adding a kernel boot parameter in Ubuntu can be done either temporarily for testing purposes or permanently. It’s a powerful way to modify your system’s behavior, but it should be done with caution. Always make sure to understand what a parameter does before adding it to your kernel boot options.

What are some common kernel boot parameters that I can add in Ubuntu?

Some common kernel boot parameters include nomodeset to disable kernel mode setting, acpi=off to disable ACPI, and mem=4G to limit the amount of memory used by the system.

Can I add multiple kernel boot parameters?

Yes, you can add multiple kernel boot parameters by separating them with a space. For example, foo=bar parameter1=value1 will add both foo=bar and parameter1=value1 as boot parameters.

Can I edit the kernel boot parameters for a specific kernel version?

Yes, when you highlight a kernel in the GRUB menu and press e to edit the commands, you can add or modify the boot parameters for that specific kernel version.

How can I find out the available kernel boot parameters for my system?

You can refer to the documentation provided by your Linux distribution or search online for the available kernel boot parameters. Additionally, you can check the /proc/cmdline file to see the parameters that your kernel booted with.

What should I do if my system becomes unstable after adding a kernel boot parameter?

If your system becomes unstable after adding a kernel boot parameter, you can remove it by editing the /etc/default/grub file and running sudo update-grub again. This will revert the changes and boot the system with the default parameters.

Can I add kernel boot parameters for specific hardware components?

Yes, you can add kernel boot parameters specifically for hardware components by targeting the appropriate modules or drivers. However, it is recommended to consult the documentation or support forums for your specific hardware to ensure that you are using the correct parameters.

Are kernel boot parameters only applicable to Ubuntu?

No, kernel boot parameters are applicable to various Linux distributions, not just Ubuntu. However, the process of adding and modifying boot parameters may differ slightly between different distributions. It is always recommended to refer to the documentation or support resources for your specific distribution.

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