Machine was updated recently without problems from 42.3 to 15.1 via DVD. Windows, on the second HD, was in grub menu as before.
Today I let package updater update lots of stuff - 100+ packages - including grub and the kernel. Afterwards Windows is no longer on the grub menu.
This only a minor inconvenience for me - I can boot windows from the machine’s boot menu so I probably won’t bother to fix it. But it looks like something is amiss with the grub update.
I turned it on and … Windows was back on the boot menu!
Isn’t that odd? I had rebooted at least once after it disappeared and then I booted into Window by calling the bios boot menu (F12) to check it was still there. Later I booted it into the grub menu to compare the kernel versions with another machine, but didn’t load SUSE.
os-prober reports /dev/sdb:Windows 10:Windows:chain
Probe foreign OS is selected
Perhaps the disk was physically stuck until I used it?
Well for me it has been the first time. Just so glad I saw the post today as I was about to ask the question. Whatever happened to others, it does appear my problem started after an update earlier in the day so grateful thanks to all once more for excellent advice and the simple solution.
Yes, that’s about right. The menu is generated by running
grub2-mkconfig -o /boot/grub2/grub.cfg
When you change something with Yast bootloader, that is automatically run. Or when you update your system, it might be run (depending on what was updated). Or you can run that at the command line. Apart from that, the menu should not change.
If you have more than one linux system installed, then you do really need to be aware which of those controls the boot menu.