It was a replacement drive. The old DAT-tape couldn´t take backups larger then 4 Gb, and the mumps-database was to be enlarged. So I was replacing it with a DLT-tape (15 Gb uncomp.)
I removed all drivers before adding anything else. I've heard of strange problems with scsi-tapes if you don't remove old tape, relink, reboot, add tape, relink, reboot, So I even did that.
I tried different ways of booting the old kernel from boot: but I never realised I had to specify the hd(40) first. I'll remember that stan. thanks.
I entered the boot/root floppy, mounted root fs and renamed unix.old to unix. That should do it, I thought.
rebooted and it still tried to load the bloody driver.
I know I didn´t relink the kernel twice, so the unix.old should be ok?
If I renamed unix.safe (and how fun do you think that kernel was?

) to unix, it booted all right.
I ran mkdev tape and removed the faulty tape with the weird driver. relinked and rebooted. AND IT STILL TRIED TO LOAD THE DRIVER.
I tried a little back and forth. I never understood how to make it go away. Isn't the kernel responsible for all those things loading after Boot:
%serial
%cpu
and so on?
Why did it try to load the driver, when I had removed all devices in mkdev tape
I found two tapes containing root and stand library, which I made when I installed the machine in november 2000.
I've never made any major changes since I installed the machine, have I? I said to myself.
My god, there was a LOT of stuff missing. certain users not added, the NIC was configured with an old IP, backup-scripts in crontab gone, semaphores misconfigured, NFS-mounting not present, no printers added. To name a few problems.
It was a long night but now it´s up and running.
/Sören