Win 10 cumulative update breaks any boot loader!

I want to let you know what happened on my office desktop computer, after the Winblowz 10 update. It firstly happened Tuesday, I booted Windows and it updated in the backgroud. After 30 minutes, when I rebooted back it has installed the Win 10 H20 cumulative update (latest). It rebooted and while it reached 98 % of the operation, it reported a failure and announced it will reinstate the initial state files. After doing that, I could not boot anymore into the system. I use ArchLabs with a / btrfs partition and 2 subvolumes, plus an extra /home partition with two subvolumes (plus /swap). The computer is a refurbished HP Intel Xeon motherboard with 32 GB of RAM, a 256 GB SDD and a 2 TB HDD. The SDD host the /efi system partion, a 98 GB Win 10 partion and a 132 GB btrfs / partition. Win10 was completely down, the boot disk reported can’t perform any repair. I tried to boot into ArchLabs using the boot disk and it reported the / partion as empty (it has been formatted). I reinstalled Win 10 and then ArchLabs. Refind could only launch Win 10, it refused to boot into ArchLabs. I tried to use grub as a boot loader and it only saw ArchLabs, grub-mkconfig could not detect Win, even if ntfs-3g was installed and the root windows partion was reported as loaded. I booted into ArchLabs with grub and then reinstalled refind. It went smoothly, I was able to see both systems, but any attempt to boot Win10 led me to the situation in which refind could not boot anymore (it did not launch). And the only thing reported was the Win boot manager. I tried to enter into rescue mode using the ArchLabs live USB disk. Atfer mounting the root partition as /dev/sdaX and the boot partion as /dev/sdaY, any attempt to run into arch-chroot mode gave me errors on proc not being mounted or sys or dev. I reinstalled again ArchLabs and it was the same. I could not enter rescue mode. I then decided to try the Arch Linux USB disk, installed ArchLinux from scratch creating not only a /home btrfs partion but also a /snapshots btrfs partition. I installed refind, everything went smoothly and I could boot into Arch Linux. After returning to Win 10, refind did not work anymore and the boot F9 key reported only Windows Boot manager. This time I was able to enter into rescue mode with the USB Arch Linux disk, mounted the / and /boot partition (/mnt/boot), ran arch-chroot and reinstalled refind. So I could boot again into Arch. Any Win 10 boot destroys the bootloader (either grub or refind) after the last cumulative update, and one has to enter rescue mode, then reinstall the boot loader. I consider the issue as extremely serious and hope my topic will be of help. All the best from here, Bogdan

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