Hey Kees!

 KvE> After installation I disable autostart of X, en enable ssh.

The nice thing about growing your own is that nothing needs disabling since it
never got built in the first place.

Mind you nathing for arm ... yet.  :::evil grin:::

 KvE> there is also a company that builds a special "shield" with a GPS
 KvE> receiver for this purpose.

This sounds interesting.  So far I've only identified one reciever that might
work out for this idea and have yet to take the plunge.

 KvE> It cannot compete with a tier one server, but it works.

Please define 'compete'.  Have you ever priced out a half-decent time server? 
It wouldn't be too far of a stretch to claim building 100's of RasberryPi
systems for the same cost as one.  There is nothing running here that requires
better than up to the second accuracy and probably not even that.  It should be
doable.

Life is good,
Maurice

... Don't cry for me I have vi.
--- GNU bash, version 4.3.30(1)-release (x86_64-atom-linux-gnu)