Windows disappeared from grub after CentOS

Question

So, I installed CentOS 8 after having Windows 10 on it. I initially had an M2 ssd of 500GB. After partition the disk and installing CentOS, my windows is no longer an option when I boot. I have been trying to solve this for a longer time that I am willing to admit. The things that I have tried:

1. steps from here: https://unix.stackexchange.com/questions/169787/windows-boot-option-is-missing-after-installing-centos-7-how-can-i-get-it-back, which are essentially:

sudo yum install epel-release
sudo yum install ntfs-3g
sudo grub2-mkconfig > /dev/null
sudo cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.old
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

2. From centos i see that windows is mounted on /dev/nvme1n1p3 and i saw that hibernate file is there, so i probably haven't turned off windows properly when i was installing centos. So, i removed hibernate file using

remove_hiberfile

and did step 1 again. No luck.

3. I followed the steps from : https://dareneiri.github.io/Configuring-Grub-2-on-CentOS-7/ , which is essentially changing 40_custom to add menu entry to grub. Also did not work for me.

My final approach is that i bought second 1TB M2 ssd (i have two slots on the motherboard) and now I want to migrate my work into the 1TB ssd, purge centos from the 500GB M2 and hopefully i could retrieve my windows that way. I am looking for a) will it solve my problem (getting my windows back) ? b) if yes, how would i go about doing that? c) ideally, i would like to make selections via grub and not via UEFI boot loader menu, but at this point i will be just happy having windows back.

Thank you

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Answer 1

yes i did the same and it did not work! (at first) !!!there are 2 files to be edited (read further) and also you have to be LOGGED as root not as simple user! and use FILES folder! not sudo crap..whatever!

so I realized he says hdo,1 but is in fact 2!! also, you have to login as root!! USER: root then you use the FILES app from Centos go to file..add...whatevet they said chainloader...etc.. then go back in TERMINAL execute/..mkconfig.....line...

and then restart

BUT!!!! also you have to add the >>>> If a default boot entry into Windows (or something else) is requested, then you need to edit the GRUB_DEFAULT in /etc/default/grub: GRUB_DEFAULT="Windows xxx"

everything like in https://dareneiri.github.io/Configuring-Grub-2-on-CentOS-7/

but 2 instead of 1 in my case WIn10 has usually 3 partition the first small is Recovery, 2 is for boot but YOU DO noT PUT this one! and 3 is the WINDOWS main one the big one...THIS IS the ONE!

but because the STRING starts with 0 not 1..you have to Put 1 for second, 2 for third etc...got it?

anyway it worked!