How to Permanently Disable the Internal Laptop Screen in Ubuntu via GRUB

Why Disable the Internal Screen via GRUB?

Many users transform their Ubuntu laptops into desktop workstations by connecting them to external monitors, keyboards, and mice. While you can disable the internal laptop screen through the standard Ubuntu Display Settings GUI, this software-level configuration only applies after you log in. The internal screen may still power on during the boot sequence, display the login screen, or cause window management issues if the system gets confused about the primary display. To permanently hardware-disable the internal display at the bootloader level—ensuring the system only ever recognizes the external monitor—you can append a specific video parameter to your GRUB configuration.

Identifying Your Internal Display Name

Before modifying GRUB, you must find out exactly what the Linux kernel calls your internal laptop screen.

1. Open your Terminal.
2. Run the following command to list all connected and disconnected video outputs:

   ls /sys/class/drm/

3. Look for entries that end with a status file. More easily, you can just use xrandr or wayland tools, but a reliable kernel method is reading the status of the DRM connectors.
4. Run this command to print the status of all displays:
5. for p in /sys/class/drm/*/status; do con=${p%/status}; echo -n "${con#*/card?-}: "; cat $p; done
6. Identify the internal display. It is usually named something like eDP-1, LVDS-1, or eDP-2. Take note of this exact name.

Modifying the GRUB Configuration

Once you know the name of your internal display (e.g., eDP-1), you can instruct the kernel to disable it during boot.

1. Open the GRUB configuration file in a text editor with root privileges:

2. sudo nano /etc/default/grub

3. Locate the line that begins with GRUB_CMDLINE_LINUX_DEFAULT=. It usually contains parameters like “quiet splash”.
4. Inside the quotation marks, add the parameter to disable your specific display. The syntax is video=[display_name]:d. For example, if your display is eDP-1, you would add video=eDP-1:d.
5. The line should look something like this:
6. GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=eDP-1:d"
7. Save the file by pressing Ctrl + O, hit Enter to confirm the filename, and then press Ctrl + X to exit nano.

Updating GRUB and Rebooting

You must update the GRUB bootloader for the changes to take effect.

1. Run the update command:

   sudo update-grub

2. Wait for the process to complete and generate the new configuration file.
3. Restart your laptop.

Upon rebooting, the kernel will completely ignore the internal display. The boot sequence, login screen, and desktop environment will output exclusively to your connected external monitor, acting exactly as if the laptop screen does not physically exist.