RTAI for Stretch/Buster and rabbit holes

I spend the day trying to get a version of either Debian Stretch or Buster with RTAI and 2.8 working. I have a preempt version of Stretch with 2.8. I have looked at many different posts and followed several different sets of instructions all of which lead to one impasse or another. That lead me to the question of what do I need to do to get from Stretch preempt to RTAI? Can I get pre-built kernel or do I have to build it myself? About 8 months ago I did get through the process of building a preempt kernel but this one has just beat me.

Thanks
John

I'll try that one again tomorrow.

John

Tried again and made it to "REBOOT". Then it would no longer boot. It gives an error: "kernel not compile with retpoline; no mitigation available"

I does mention BusyBox v1.22.1 on the screen and I end up at what looks like a prompt (initramfs). At this point it does not accept input from the keyboard.

$ sudo make
$ sudo make install
$ sudo make modules_install
On debian this will automatically update grub and set the system to boot from the new kernel.
REBOOT (and check with uname -r that the new kernel is running: 4.14.132-rtai-amd64
If it boots to the busybox boot to the old kernel then run these commands JT

cd /usr/src/linux
sudo make modules_install
sudo make install

I did find them and installed the image and headers but it still shows as PREEMPT.
When booting in complains that the kernel is not compiled with "Retpoline" no mitigation available.
I guess that is OK but possibly risky.
$ cat /sys/devices/system/cpu/vulnerabilities/spectre_v2
Vulnerable, IBPB: disabled, STIBP: disabled

Am I just not understanding how to tell if this is RTAI or PREEMPT?

Linux X3CNC 4.14.148-rtai-amd64 #2 SMP PREEMPT Sat Nov 9 16:29:10 GMT 2019 x86_64 GNU/Linux

I also tried these and it boots with the same warning..

linux-headers-4.14.132-rtai-amd64_4.14.132-rtai-amd64-1_amd64.deb
linux-image-4.14.132-rtai-amd64_4.14.132-rtai-amd64-1_amd64.deb

Thanks
John