Dual Boot Help (Win10 and CentOS8)

Question

Please help me guys. I'm losing my mind trying to dual boot my machine.

Here is the specs of my machine:

acer 4755g
SSD for windows 10 and  HDD for CentOS 8 (partition, not whole disk is used)

Problem:

CentOS grub cannot detect windows 10 bootloader.

Here are the steps that I have done to correct it:

Installed ntfs-3g and ran sudo grub2-mkconfig > /dev/null. It still does not see the windows boot loader. In fact, sudo grub2-mkconfig > /dev/null returns nothing.
Also tried to manually add chainloder on grub, still nothing.
os-prober does not return anything

Possible reason for the problem

Windows 10 is installed using BIOS and CentOS is using UEFI

I'm just confused on how CentOS managed to install UEFI on my machine. I'm pretty sure that my machine only supports BIOS. Note: To make the bootable USB, I used rufus with the MBR option.

FINAL NOTE:

I think if I convert the bootloader of CentOS from UEFI to BIOS, this problem will be solved.
But can it be converted and How?

Alexander Rumyankov · Answer

I had the same issues with Windows 10 and Ubuntu 20.04 (and Centos 8)
Following steps are applicable for any Windows 10 and Linux dual-boots.
Please check that your laptop supports UEFI, UEFI enabled in BIOS and Linux is installed in UEFI mode.

Install Window 10

Install Linux

Install os-prober to Linux (if not installed)

Boot into Windows 10

Disable fast boot and hybernate. Run in elevated cmd:
powercfg.exe /hibernate off

Reboot in recovery mode (press Shift and choose Reboot)

Choose command line (in recovery mode) and enter:
mbr2gpt.exe /convert
Please note, that you will not able to boot Windows without UEFI in this case.

Boot into Linux and update grub depending on your Linux
For CentOS8:
grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg
Generating grub configuration file ...
Found Windows Boot Manager on /dev/sda1@/EFI/Microsoft/Boot/bootmgfw.efi
done
For Ubuntu:
os-prober
update-grub2

You can now reboot and see Windows Boot Manager in GRUB menu

Mani · Answer

Have you installed ntfs support? Here is what worked for me:

sudo yum install epel-release
sudo yum install ntfs-3g

Then make a copy of your grub configuration file:
cd /boot/grub2

sudo cp grub.cfg grub.cfg.bak

and finally create a new grub configuration:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

Michael Shigorin · Answer

Yes, looks like BIOS/UEFI mix; refind built with the other toolchain, not GNU EFI (forgot the name, sorry), can support booting BIOS/CSM/Legacy targets from EFI mode.

But I'm pretty sure you'd prefer to have that dualboot aligned with regard to firmware in the end, be it BIOS/BIOS or UEFI/UEFI; it is NOT possible to install UEFI bootloader on BIOS-booted system (even if it's an UEFI-capable system in "legacy" mode).

See also Refind's author's excellent explanation of UEFI bootloaders, it helped me implement UEFI support in ALT Linux back then.

Dual Boot Help (Win10 and CentOS8)

3 Answers

Add your own answers!

Ask a Question