Grub not shown on external screen after installing Arch Linux on old laptop

Understanding the Display Initialization Timing

The core issue lies in the sequence of events during the boot process. When a laptop is connected to an external display via HDMI or DisplayPort, the system must initialize the graphics hardware and detect the connected monitors before rendering the GRUB interface. In many cases, particularly with older laptops or specific GPU architectures (like NVIDIA Optimus or AMD hybrid graphics), the external port may not be fully powered or detected until the operating system loads its proprietary drivers. Since GRUB runs in a pre-boot environment with minimal drivers, it often defaults to the internal eDP/LVDS panel if it cannot immediately handshake with the external connector.

This behavior is distinct from a complete failure to boot. If you can see GRUB on the laptop screen but not the TV or monitor, the system is functioning correctly; it is simply directing the visual output to the wrong endpoint. This is rarely a "bootloader recognition" issue as described in some general troubleshooting guides, but rather a display configuration nuance within the UEFI firmware or the GRUB video subsystem.

Configuring GRUB Video Modes

The most effective software-based fix is to force GRUB to use a standard VGA-compatible text mode that all monitors can understand, rather than relying on high-resolution framebuffer modes which might not be supported by the external display's EDID (Extended Display Identification Data). To do this, you need to edit the GRUB configuration file.

1. Open the terminal and edit the main configuration file:

sudo nano /etc/default/grub

2. Locate the line starting with GRUB_GFXMODE. If it does not exist, add it. Set it to a standard resolution such as:

GRUB_GFXMODE=1024x768

3. Ensure that GRUB_GFXPAYLOAD_LINUX is set to keep the same mode:

GRUB_GFXPAYLOAD_LINUX=keep

4. Save the file and exit the editor.
5. Update GRUB to apply the changes:

sudo grub-mkconfig -o /boot/grub/grub.cfg

This forces GRUB to render in a basic mode that is universally compatible with both internal laptop screens and external monitors. After rebooting, check if the external display now shows the menu. If it does, you can gradually increase the resolution in GRUB_GFXMODE to find the highest native resolution your setup supports.

Adjusting BIOS/UEFI Settings

If software configuration does not resolve the issue, the problem likely resides in the motherboard’s firmware settings. Older laptops often have a setting that determines which display device is prioritized during POST (Power-On Self-Test).

• Reboot the laptop and enter the BIOS/UEFI setup (usually by pressing F2, Del, or Esc during startup).
• Navigate to the Display, Video, or Boot tab. The exact location varies by manufacturer.
• Look for options named Primary Display, Initiate Graphic Adapter, or Multi-Monitor Support.
• If available, change the setting from Auto or LCD Only to PEG/PCIe (for discrete GPUs) or External Monitor.
• Save changes and exit.

On some systems, you may also need to disable Fast Boot in the BIOS. Fast Boot skips certain hardware initialization steps to speed up startup, which can prevent the external port from being recognized in time for GRUB to render on it. Disabling Fast Boot ensures a more thorough hardware handshake at power-on.

Using Kernel Parameters for Early Console Switching

In rare cases where the above methods fail, you can instruct the Linux kernel to switch the console output to the external display as early as possible. This requires adding a parameter to the GRUB command line.

1. Edit /etc/default/grub again.
2. Find the GRUB_CMDLINE_LINUX_DEFAULT line.
3. Add video=HDMI-A-1:e to the list of parameters. Note that HDMI-A-1 is a common identifier for the first HDMI port, but you may need to verify your specific connector name by checking dmesg | grep drm after booting into Linux.

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=HDMI-A-1:e"

4. The :e flag forces the mode to be enabled. Save the file and run sudo grub-mkconfig -o /boot/grub/grub.cfg.

This method tells the kernel to explicitly enable the specified HDMI output during the early boot phase, ensuring that when GRUB hands over control to the kernel, the external screen is already active and displaying the console.

Frequently Asked Questions

Why does GRUB show on the laptop but not the TV?

This happens because the default video output is set to the internal display controller. The system initializes the internal screen first, and since GRUB binds to the first available active output, it ignores the external monitor until the OS takes over. Forcing a standard VGA mode in GRUB often resolves this by making the output compatible with both displays simultaneously.

Can I fix this without editing config files?

Yes, primarily through BIOS settings. Disabling Fast Boot and manually selecting an external display as the primary output in the UEFI firmware can solve the issue without touching Linux configuration files. This approach ensures the hardware initializes the external port before any software like GRUB attempts to render graphics.

What if my external monitor has a different aspect ratio?

Setting GRUB_GFXMODE to a universal resolution like 1024x768 or 800x600 avoids aspect ratio mismatches. High-resolution modes tailored for modern 16:9 monitors may cause black bars or no signal on older projectors or TVs with different native ratios. Using a lower, standard resolution ensures compatibility across diverse display types.

Does Secure Boot affect GRUB display on external monitors?

No, Secure Boot affects the cryptographic verification of the bootloader and kernel modules, not the graphical output routing. While Secure Boot must be disabled to load third-party drivers (which might indirectly help with GPU initialization), it does not directly control which physical screen receives the GRUB image.

How do I find the correct HDMI connector name for kernel parameters?

Once booted into Arch Linux, open a terminal and run ls /sys/class/drm/. Look for entries starting with card0-HDMI- or card0-DP-. The number following the dash (e.g., -1) is the index you use in the video=HDMI-A-X parameter. You can also check dmesg | grep [vV]ga or dmesg | grep [dD]rm for detailed initialization logs.