RHEL installation made Windows unbootable

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I just installed RHEL 6.10 on my workstation, which also run MS Windows 8.1. Unfortunately, the installation rendered my Windows unbootable. I need help to fix the problem; any helpful suggestions you can give are most appreciated.

I don't have fancy disks (like LVM or SCSI); I have a single disk with 28 partitions (GPT). The C:\ drive for Windows is on /dev/sda5, so that's the address I gave the bootloader for the other OS to boot. When my machine starts, the bootloder menu shows the WinOS option along with RHEL, but when I select it, I get the error message: "EFI path must be a full path, or ...". Then I checked the config file /boot/efi/EFI/redhat/grub.conf, and it looks reasonable. Here is what it says:
title WinOS
rootnoverify (hd0,4)
chainloader +1

Much thanks in advance, if you can help.

Responses

The error messages about EFI paths indicate the system is using UEFI.

"chainloader +1" would be valid for versions of Windows with traditional BIOS-style boot. But for Windows versions using UEFI, it's not appropriate. On UEFI systems, the "chainloader" line should be:

chainloader /EFI/Microsoft/Boot/bootmgfw.efi

And the partition specification for the UEFI WinOS entry should not point to the Windows C:\ drive, but to the EFI System Partition (ESP for short). In Windows, this normally has no drive letter at all.

Thank you very much, I appreciate your help! I will try your suggestion this evening as soon as I return home from work (where I am now.)

Thank you, I tried it and it worked like a charm. (Actually it did not work the first time, but then I figured out that I had to add a "root (hd0)" statement on the previous line.) So, all is well now, and I finally have a dual boot machine. Thanks for your help.

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