In a dual OS PC, How to make the second OS invisible when running the boot loader and how to restore it when needed

Question

In my pc, there are two operating systems in two partitions. Thus, the boot loader shows all of them when starting the PC. I want to make the boot loader run one OS in order to hide the existence of the other one. But when needed, I should be able to restore the original boot loader that shows all the existing operating systems.

I am thinking about two different copies (images) of the MBR sector. The first one corresponds to the first OS (Taken before installing the second OS), while the second one corresponds to the dual boot OS (Taken after installing the second OS). I am not sure if the MBR sector is sufficient. Maybe other sectors are needed.

Answer 1

One way to do this would be to rename the .efi file that first boots. E.G., you might rename shimx64.efi or grubx64.efi or whatever is the default bootloader, to grubx64.efi.old, and the original Microsoft Windows bootloader, perhaps bootmgfw.efi, to that of the Grub EFI file.

This would "hide" the Linux OS, in the sense that the PC would boot directly to Windows, until you renamed the files back. However, the Linux partition would show in any disk management tool, so this is not very effective.

To rename the file, you can use Windows tools, or a third-party tool such as DiskGenius.

Keep a bootable USB drive with copies of the bootloader files and with disk management tools hand. If something goes wrong, these can help you recover normal dual-boot operation.