HP 8200 Elite CMT won't boot Linux entry (boots Windows instead)

[tokenslol]

I have been able to dual boot Windows 10 and Linux (different distros) in the past, but my last installation hasn't been able to boot. BIOS is updated to v2.33, and both installations are on separate drives.

Specifically:

- Windows 10 LTSC IoT installed on a 1 TB SSD (Samsung 870 EVO)
- CachyOS installed on a ~300 GB HDD (WDC WD3200AAJS-22L7A0)

Installation from a bootable USB appears to complete just fine. I could see from the live environment that the HDD had its own EFI partition with EFI/cachyos/grubx64.efi, and that the drive could be mounted and read without any issues.

I also used efibootmgr to manually create a boot entry pointing to EFI/cachyos/grubx64.efi, and it appears in the boot menu as expected. This is where things got increasingly more unusual:

- Selecting the CachyOS boot entry boots Windows instead of GRUB.
- Run UEFI Application can browse the USB drive and the SSD, but the HDD does not even appear.
- The same happens in Device Configuration (F10), where the SSD is listed but the HDD is not.

I should also mention something I observed before this particular installation.

Previous Linux installations on this same HDD booted correctly. At some point, without reinstalling Linux, changing BIOS settings, or updating the BIOS, the machine stopped booting through GRUB and instead began booting directly into Windows.

When I later wanted to remove Linux, I couldn't wipe the HDD from Windows because Windows treated the HDD's EFI partition as being in use. I had to wipe it from a Windows installation USB instead. Around the same time, I also noticed that the BIOS Boot Order only listed the Linux entry. Disabling it caused the Windows boot option to disappear from the boot menu as well.

At this point I'm unsure whether this problem falls more on Linux or on the HP firmware. Has anyone seen this kind of behavior on this machine (HP Compaq 8200 Elite CMT) or on other HP systems from the same generation?

I considered cleaning things up before making this post, but I didn't want to remove the evidence that might help identify the cause.

[Deep_World]

Hi   @tokenslol,
 
Welcome to the HP Support Community!

Thanks for reaching out!

I hear your concern that the system previously dual-booted Linux and windows suddenly starts booting directly into Windows.

To better understand the issue and provide the most appropriate guidance, could you please confirm the following details:

• Is Secure Boot enabled or disabled in the BIOS?
• Is the system configured for pure UEFI mode or Legacy BIOS mode?
• Have you tested with another HDD or SSD containing a Linux installation to see if the behaviour is the same?

Based on the information you've provided, there are a few observations worth checking:

1. Verify Drive Detection in BIOS
   Since the HDD does not appear under Device Configuration or "Run UEFI Application," please check whether the BIOS consistently detects the drive.
   Try connecting the HDD to a different SATA port on the motherboard.
   If available, test with a different SATA cable.
2. Load BIOS Defaults
   • Enter BIOS Setup (F10).
   • Select "Restore Defaults" or "Load Setup Defaults."
   • Save changes and reboot.
   • Reconfigure any necessary settings afterward.
3. Check Boot Order
   • Ensure the Linux EFI entry appears separately from the Windows Boot Manager.
4. Hardware Health Check
   • Since the HDD is not consistently visible within certain BIOS menus,Try to run diagnostics on the drive and review SMART status to check for  hardware issues.

Please note that HP provides limited support for Linux operating systems on older consumer and commercial platforms.  If the issue persists after the hardware and BIOS checks above, we recommend contacting the Linux support team.

I hope this helps.