Contiguous Win 10 and Debian boot partitions = unbootable Debian but win ok

[herm]

Disk 1 partitions: system reserved + Debian boot + Windows 10 (all primary)
Disk 0 partitions: 8 logical partitions (1/2 Win 1/2 Debian) in extended partition.
BIOS-based, MBR system.

BIBM version 1.85 --- Result: Windows boots ok,
BIBM says Debian /boot not bootable.
Does not depend on limiting primaries or not.
/boot does contain the Grub boot manager files. (checked)

I can't understand this at all. (I have used BIBM for some years with few problems) ... Am I doing something stupid
Any comment very welcome. TIA.

[TeraByte Support]

Follow the process at https://www.terabyteunlimited.com/kb/article.php?id=278

Key is where the kernel loader (typically GRUB2 now) is placed. MS OS always has their kernel loader start from the boot sector as was intended in the PC design, Linux was always the odd ball with that.

[herm]

Thanks for the quick reply. You are correct the problem was installing Debian Linux before reinstalling BootIt and not controlling the partitions visible to BootIt.
Following carefully the advice in "Linux Installation Notes: Debian" solved the problem which was rather obscure and doesn't always occur.
So, thanks again and best wishes for 2021.