Dual Boot RHEL 7.4 and Windows 10

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I bought a new laptop. I wanted to dual boot Windows 10 and linux although it is unsupported. I installed CentOS 7 which worked but didn't allow me to boot into Windows 10. So I did a clean reinstall of Windows 10 then installed RHEL 7.4. The RHEL installation seemed to go well. I chose default to get automatic partitioning and entered other values as required. It seemed to install but upon boot I don't get a grub menu offering a choice of linux or win 10. I booted into the rescue environment and ran grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg. It shows 5 lines saying that it has found everything but still no grub menu upon reboot. I'm lost. Would a reinstall of RHEL work? Any help would be appreciated.

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Hi Richard,

Say, please examine this other discussion https://access.redhat.com/discussions/2908301 where some info on this might be useful.

From what I recall in the times (in the distant past) when I did dual boot, that I did install windows first as you did, then Linux. I'll see if I can come up with any more, but hopefully something in that other discussion might help

Regards,

-RJ

Hi RJ,

What you recall is still valid, first install Windows and then a Linux system. Windows tends to override the EFI partition, which means that Linux systems can not boot any more, because all files and folders get deleted. :)

Regards,
Christian

There's a chance this youtube video https://www.youtube.com/watch?v=0fCA7ToywoY might be similar to what you mentioned. One person said they had to remake the config. Examine the video itself, but also read the replies. This one seems to possibly be useful https://www.youtube.com/watch?v=iwwRd_oVaJA.

I see you've done some of this, but examine it and let us know how it goes.. someone ought to chime in and help.

Hi Richard,

RJ is right, you most probably will find the solution in the other thread. Among the instructions there is what is important in your case - you said : "I chose default to get automatic partitioning ..." That means you have 'wiped' the whole disk to be used for RHEL exclusively. Please create the partitions with GParted before installing a system - then first install Windows and afterwards RHEL.

In both cases select manual (custom) partitioning, disable Secure Boot, and also disable Fast startup and Hibernation in Windows. Shutdown the machine completely, boot to BIOS and select RHEL as default system. Now everything should work as expected. :)

Regards,
Christian

Thanks for all the help. After many reloading attempts I have found some things. First I installed Windows 10 first then RHEL 7.4. Although I chose defaults it did not overwrite the windows partition on the the hard disk. Still I created the partitions manually as suggested. If I then run grub2-mkconfig -o /boot/efi/EFI/Microsoft/Boot/grub.cfg or /grub2-install /dev/sda then the system boots directly into Windows 10 with no grub menu shown on boot and there is a new entry in the bios of Windows Loader. If I boot RHEL as a repair entry off the RedHat 7.4 iso disk and go in and erase /dev/efi/EFI/Microsoft and the child directories the Grub2 choices for linux and windows appear. There is an entry in Grub2 for Windows 10 which won't work but at least I can access my linux system. Why does the entry appear in the bios for windows bootloader and why can't I access the grub menu after grub2-install or grub2-mkconfig? I can access both partitions now but changing partitions is a problem. I still need help. Thanks.

Hi Richard,

Every operating system has its own boot loader which gets installed to a separate folder on the EFI partition, so grub2-mkconfig -o /boot/efi/EFI/Microsoft/Boot/grub.cfg makes 'no sense'. The correct command would be sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg. The reason why the machine boots directly to Windows is that in Windows most probably Fast startup and Hibernation is enabled (default setting after fresh installation). Disable Fast startup in system settings, disable Hibernation with powercfg -h off (command prompt as administrator). Shutdown the machine completely (don't reboot). Then start the machine, boot into BIOS and select RHEL as default system. In case there are wrong entries in the boot menu options, you can check this with sudo efibootmgr -v. You can delete the wrong entries with sudo efibootmgr -b <ID> -B (ID = e.g. 0003). :)

Regards,
Christian

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