Fixing Windows 11 Black Screen Issues With IPXE And Sanboot

Are you pulling your hair out because of a Windows 11 black screen when booting through iPXE using sanboot? You're not alone! Many users have experienced this frustrating issue after upgrading from Windows 10. This article dives deep into the problem, exploring potential causes, and providing effective troubleshooting steps to get your systems booting smoothly again. Let's get started!

Understanding the Black Screen Problem

After upgrading a significant number of hosts from Windows 10 to Windows 11, a peculiar problem arises: some machines, especially those with smaller screens, get stuck on a black screen during the boot process when using iPXE with sanboot. You can see the mouse cursor, indicating the system is partially responsive, but nothing else happens. This is a common situation, and we’ll get to the bottom of it.

The core of the problem seems to be an incompatibility or misconfiguration between iPXE, sanboot, and the way Windows 11 handles the boot process. The iPXE script is supposed to load the operating system, but in this scenario, it fails to display the boot sequence correctly, resulting in a black screen.

The usual iPXE boot entry used is as follows:

#!ipxe
console && sanboot --drive 0 --filename \EFI\Microsoft\Boot\bootmgfw.efi

This script first sets up the console and then uses sanboot to boot from the specified drive and file, which is the Windows bootloader. The console command was previously added to fix display issues on some screens, but it doesn't seem to resolve the current problem.

When you boot using the native UEFI entry, “Windows Boot Manager”, everything works fine. This means the underlying hardware, firmware, and the Windows installation itself aren’t the main issue. It’s something specific to the iPXE boot process interacting with Windows 11.

Upgrading iPXE to the latest commit (c8f088d4e11a1dedda4829c4be1bb1b14e9da016) doesn't solve the problem, indicating the issue may lie deeper than a simple iPXE bug.

Diagnosing the Root Cause: iPXE, sanboot, and Windows 11

To effectively troubleshoot, we need to understand the relationship between iPXE, sanboot, and Windows 11's boot process. Here's a breakdown:

• iPXE: A powerful open-source network boot firmware. It allows computers to boot from a network server instead of a local storage device.
• sanboot: An iPXE command that allows booting from a Storage Area Network (SAN), essentially treating a network-based storage as a local hard drive.
• Windows 11 Boot Process: Windows 11's boot process has evolved over previous versions, including changes to how it interacts with UEFI and the bootloader. It's possible that the standard sanboot configuration isn't fully compatible with the nuances of Windows 11's boot sequence.

Several factors can contribute to the black screen issue:

1. UEFI Compatibility: Ensure your iPXE firmware is fully compatible with your system's UEFI implementation. Older iPXE versions might have compatibility issues with newer UEFI versions used in Windows 11 systems.
2. Graphics Driver Initialization: There might be a problem with how the graphics drivers are initialized during the iPXE boot process, especially with certain display adapters. This could lead to a black screen, even if the system is otherwise operational.
3. Bootloader Interaction: The sanboot command might not be correctly interacting with the Windows 11 bootloader (bootmgfw.efi), causing it to fail to load the operating system properly.
4. Display Configuration: Sometimes, specific display configurations or resolutions set during the boot process can cause the black screen. The console command is designed to fix this, but in some instances, it might not be enough.
5. Timing Issues: There could be timing issues in the boot sequence, where certain drivers or services are not loaded in the correct order, leading to a black screen.

Troubleshooting Steps and Solutions

Now, let's explore some practical troubleshooting steps to resolve the Windows 11 black screen problem when booting via iPXE and sanboot. Try these solutions sequentially to pinpoint the cause and find a working solution.

1. Update iPXE Firmware

As a first step, ensure you're using the latest, or at least a recent, version of iPXE firmware. While you’ve already updated to the latest commit, it's worth re-verifying that the update process was successful and that the new firmware is correctly loaded on your affected machines. You may want to consider building your own iPXE binaries to ensure it's compiled with the right settings for your hardware.

2. Verify iPXE Script and Parameters

Double-check your iPXE script and parameters. Sometimes a small typo or an incorrect setting can cause significant issues. Confirm that the path to the bootmgfw.efi file is correct and that the drive number (--drive 0) is accurate. Make sure the iPXE script is correctly configured to handle the specific hardware and boot requirements of Windows 11. It's important to verify that there are no errors in your script as a starting point. An easy-to-miss mistake can lead to the black screen.

3. Experiment with Different Boot Options

Try different boot options and combinations within your iPXE script. Experiment with the following:

• Remove the console Command: Although the console command was added to fix screen issues, it might be interfering in some cases. Try removing it to see if it resolves the issue.

  #!ipxe
  sanboot --drive 0 --filename \EFI\Microsoft\Boot\bootmgfw.efi
  

• Use chain Command: Try using the chain command to directly load the bootloader:

  #!ipxe
  chain --filename \EFI\Microsoft\Boot\bootmgfw.efi
  

• Specify the Drive: Sometimes, explicitly specifying the drive can help:

  #!ipxe
  sanboot --drive 0x80 --filename \EFI\Microsoft\Boot\bootmgfw.efi
  

• Include Debugging Information: Add verbose output to your iPXE script to see if you can identify where the boot process is failing. This can involve using the echo command to print messages or using conditional statements to check different stages of the boot process.

4. Check UEFI Settings

Review your UEFI settings on the affected hosts. Ensure that:

• Secure Boot is Disabled: Secure Boot can sometimes interfere with iPXE and sanboot. Try disabling Secure Boot in the UEFI settings and see if it helps.
• Boot Order is Correct: Make sure iPXE is set as the primary boot option in your UEFI settings. The system should attempt to boot from the network before any local devices.
• CSM (Compatibility Support Module): Some older systems may require enabling CSM in the UEFI settings. However, enabling CSM might cause other issues. Test both with and without CSM enabled.

5. Verify Network Configuration

Incorrect network configuration can also lead to boot problems. Ensure that:

• DHCP is Properly Configured: Your DHCP server must be correctly configured to provide the necessary information (IP address, gateway, DNS server) to the client machines.
• TFTP Server is Accessible: The TFTP server, where iPXE loads its firmware, must be accessible to the client machines. Check your firewall settings to make sure TFTP traffic is allowed.
• Network Drivers: iPXE must have the correct network drivers for your hardware. Verify that the correct drivers are included in your iPXE build.

6. Test with a Different Windows 11 Image

There could be an issue with the specific Windows 11 image you are using. Try using a different, known-good Windows 11 installation image. This helps to rule out corruption or other problems with the image. If the new image boots successfully, the problem is likely with the original image.

7. Monitor the Boot Process with a USB Capture

Use a USB capture device or a serial console if possible. This way, you can see the text output during the boot process. This can often reveal the exact point where the boot fails. A serial console will provide a low-level view of the boot process, which can be invaluable for identifying the source of the black screen.

8. Review Hardware Compatibility

In some cases, specific hardware configurations, especially graphics cards or network adapters, might have compatibility issues with iPXE and Windows 11. Ensure that all the hardware components are compatible with the Windows 11 environment. Check for any known hardware-specific issues and whether there are any driver updates available.

9. Check for Firmware Updates

Make sure that your system's BIOS/UEFI firmware is up-to-date. Newer firmware versions often include fixes for compatibility issues and can improve the boot process.

10. Seek Community Support

If you've tried all the above steps and are still experiencing the black screen issue, consider reaching out to the iPXE and Windows communities. There are active forums, mailing lists, and social media groups where you can seek help from other users who have encountered similar problems. Be sure to provide detailed information about your hardware, iPXE version, iPXE script, and any troubleshooting steps you've already tried.

Advanced Troubleshooting

If the basic troubleshooting steps don’t work, delve deeper into the system's logs and configurations.

1. Analyze Windows Event Logs

Once you've successfully booted a machine (perhaps using the Windows Boot Manager as a workaround), review the Windows Event Logs for any errors or warnings related to the boot process. These logs can often provide valuable insights into what is going wrong.

2. Check the BCD (Boot Configuration Data)

Examine the Boot Configuration Data (BCD) settings using the bcdedit command in Windows. Make sure that the boot configuration is correctly set up for your installation. Incorrect BCD settings can cause boot failures.

3. Review the iPXE Build Configuration

If you're building iPXE from source, review your build configuration. Make sure you've included all the necessary drivers and modules for your hardware. A custom iPXE build might be required for optimal compatibility.

Conclusion: Resolving the Black Screen

Addressing the Windows 11 black screen issue when booting through iPXE with sanboot can be a complex process. It requires understanding the interplay between iPXE, sanboot, and Windows 11's boot processes. By systematically following the troubleshooting steps outlined in this article, you can diagnose the root cause and implement the appropriate solutions. Remember to update your iPXE firmware, verify your iPXE script, check your UEFI settings, and review your network configuration. You may also need to test different boot options, ensure your hardware is compatible, and analyze system logs. Community support is always a valuable resource. With patience and persistence, you can overcome this frustrating issue and restore smooth booting on your systems.

For further reading and additional information, consider the following resources:

• iPXE Documentation: Explore the official iPXE documentation for detailed information on commands, configurations, and troubleshooting: https://ipxe.org/
• Microsoft Support: Refer to the official Microsoft support documentation for insights into the Windows 11 boot process and related issues: https://learn.microsoft.com/en-us/windows/

By carefully examining each element of the boot process and systematically eliminating potential causes, you'll be well on your way to a functional and stable Windows 11 iPXE environment.