We address the problem of network booting: Distributed processes
boot at unpredictable times and require to start some 
distributed algorithm; we consider clock synchronization algorithms
in systems of n >= 3f+1 processes where at most f exhibit Byzantine 
behavior. Obviously, assumptions like ''there are always at most 
one third of the running processes Byzantine faulty'' do not
hold during system start-up when processes boot one after the other.
Another peculiarity of network booting is message loss, even if 
perfect communication is assumed: A message that is sent by a 
correct process could be lost because the receiver has not completed
booting when the message arrives. Using a partially synchronous model
where upper and lower bounds upon transmission and computation time
exist but are unknown, we show that a suitable modification of
Srikanth & Toueg's non-authenticated clock synchronization algorithm
can handle network booting and guarantees bounded precision both during 
normal operation and start-up. Accuracy (in the sense of clocks being
within a linear envelope of real-time) is only guaranteed, however,
if sufficiently many correct processes are eventually up and running.