Problems cloning LTSP server

[RalfGesellensetter <rgx@gmx.de>]

Dear list,

today I had to clone an LTSP server system to make it run on a faster 
machine. I did so using "cp -a", because the destination partition was 
much larger.

Of course, I adapted fstab and persistent network rules for udev.
The system comes up fine, and also gets its IPs as desired.

Alas, thin clients end up booting with TFTP timeout (dhcp working).

Now, I wonder what might have gone wrong during cloning?
Are there further steps necessary like re-creation of ssh-keys 
(due to different NICs/MAC addresses)? Or are there architecture 
dependent kernel options for LTSP (source machine was AMD64, destination 
Intel Pentium, so it runs a different kernel).

Or is "cp -a" not enough to preserve all permissions and symbolic links?

Any hint welcome,
regards
Ralf.