I have a mini-XTA box 64b Intel with UEFI disabled. It has been running Mate, W7 & W10 for some time just fine. Mate and W7 are on one SSD and W10 is on a second SSD. GRUB finds and starts these 3 fine. So I wanted to play with W11 too. I shrunk the W10 partition and installed W11 in the freed space using a USB stick. Of course MS thinks they have the only bootloader and overwrites the grub. But the MS bootloader would only recognize the W11 partition on one SSD and the W7 partition on the other SSD. I used a live Mate USB reassert grub, but it still would only find Mate, W7 & W10. So in W10 I used Easy-BCD to add a boot entry pointing to the W11 partition. Now from the grub W10 entry I get into the Windows boot loader with a W10 & W11 choice. Selecting W10 enters W10 immediately. But selecting W11 reboots first into grub and then selecting W10 grub entry again boots W11. I’d like to get to all the installed OS directly from grub. Is this doable?
From Oldfred's links I re-learned about BIOS/UEFI MBR/GPT. First, since my Linux/W7 was installed with UEFI disabled, I cant expect to use UEFI/GPT on the second disk partitions. Second, allowing windows to create partitions on its own creates multiboot problems, as each OS wants to set up multiple partitions. By pre-partitioning the entire disk, I can force W10/W11 to install everything within a single partition.
It also seemed prudent to unplug the sati cable from the Linux/W7 disk to insure there was no funny business between drives. This all works if I want to use the MS BCD to select which W10/11 I want. But I want to directly load W10 or W11 from GRUB. But there is only one BCD store on the disk (in the W11 partition). I cant figure out how to add that to the W10 partition so each has its own BCD with only one entry. Then GRUB should find both and I'd have what I want.
