Windows not Shown in Boot loader on Centos8 and Windows 10 Dual Boot

[sureshkumar_s]

Windows not Automatically showing in Boot Options post Cent os8.5 Installation dual boot Installation, I used USB drive to install (.iso) image,windows is on UEFI

Install epel, ntfs-3g, tried to add the entry in 40_custom file, grub2-mkconfig also did not help.

Note that, the USB drive is not recognized when I choose the UEFI in Boot Settings. Please help how to get the Windows

[owl102]

CentOS has to be installed in the same BIOS mode (either "Legacy" or "UEFI") as MS-Windows, otherwise the boot manager of CentOS cannot boot MS-Windows. This is neither CentOS nor MS-Windows fault, the BIOS simply cannot change the mode once a mode selection was made (by the BIOS/UEFI) during boot process.

Since it seems that you have installed CentOS in Legacy mode the answer is: You can't.

I guess you have used Rufus or a similar tool to create the USB stick. This does not work, you have to use a tool which does *not* alter the contents of the ISO file but instead simply copies it 1:1 to the USB stick. See also: https://wiki.centos.org/HowTos/InstallFromUSBkey

Afterwards you should be able to install CentOS in UEFI mode and afterwards should be able to boot MS-Windows from Grub boot manager.

[jlehtone]

Why boot Windows via GRUB, if you do have UEFI?
Surely you can have two UEFI boot entries: one for (UEFI) Windows and another for (legacy) GRUB (that loads CentOS Stream 8).
The selection of OS is then done by pressing a key to bring up UEFI Boot menu (before GRUB is loaded) and choosing the other OS from it.

That said, it is cleaner to have both OS in UEFI mode. (I have, but I nevertheless use the UEFI Boot menu as the selector.)

[TrevorH]

This does have the sound of a corrupted USB stick stripping the UEFI boot info off it so it is forced to boot in legacy BIOS mode.

[sureshkumar_s]

Thanks for your inputs,Am using lenovo ideapad 330s

Yes you are right, I have used Rufus to convert initially.. As per the suggestion here I tried to use the dd command to write and kept the boot mode as "UEFI"

No USB is detected at all

When selecting the UEFI as boot mode and Boot priority as Legacy support - it detects and I can install..still I cannot dual boot into windows..

[sureshkumar_s]

Do we need additional steps post installation of cent os and how to get the windows back - ?

[jlehtone]

kept the boot mode as "UEFI"

No USB is detected at all

When selecting the UEFI as boot mode and Boot priority as Legacy support - it detects and I can install.

I had that once. CentOS did install first, cleanly in UEFI mode. Then Windows, where installer faulted as
it could not install into the GPT-partitioned disk. This naturally was odd, since Windows UEFI requires GPT.

It did turn out that the UEFI of motherboard did not like the case of the filenames of the EFI directories
in the Windows USB. Both Windows and CentOS USB images support both UEFI and legacy boot.
Since motherboard did not regognize the EFI paths, it saw only the legacy bootloader on that Windows USB.
The most bizarre thing is that EFI paths are usually in Fat32, that supposedly ignores case.


Do you have other machines where you could test that USB? If the UEFI-mode bootloader is not seen in any of
them, then fault is in USB. If other machines can boot from it in UEFI, then ...

[sureshkumar_s]

Finally, got to show the windows boot manager and got in, I had to remove Cent OS.. Since I have lot of things in windows

One major issue was with the USB Stick which didn't have the right installer files which affected them showing in UEFI mode (using dd command to burn helped) Thanks a lot.. This is new learning for me

Secondly, Looks like it has something to do with the.iso file we download meaning streams may have some setup issue s to fit into Some BIOS setup.. Thoughts ?

[aaronm]

Are the ISO files exchanged for working ones? Please give us a corresponding message.

[sureshkumar_s]

Yes, I have downloaded the Centos-7 Linux (instead of Streams) , it was fine