clockspeed — speed up or slow down the local clock, continuously




clockspeed resets the local UNIX clock every three seconds according to (1) an internal hardware tick counter and (2) occasional real-time measurements from a reliable source.

clockspeed reads the real-time measurements from /usr/local/clockspeed/adjust. Each real-time measurement must be a single 16-byte packet, expressed as a TAI64NA time adjustment to the local UNIX clock.

clockspeed does not place any limits on the possible adjustments. It is your responsibility to make sure that the measurements are reliable.

After two real-time measurements, clockspeed can figure out the number of real attoseconds per tick. It saves this number in TAI64NA format in /usr/local/clockspeed/etc/atto, overwriting usr/local/clockspeed/etc/atto.tmp for reliability. It reads usr/local/clockspeed/etc/atto when it starts up again.

clockspeed must be run by root.


clockspeed was originally part of Daniel J. Bernstein's clockspeed toolset in 1998.


Original code and documentation by Daniel J. Bernstein. Documentation modernizations by Jonathan de Boyne Pollard.