What units does the ntp drift file use?

Solution 1:

The drift file is /var/lib/ntp/ntp.drift. This is fairly standard. For RH/Fedora, it's /var/lib/ntp/drift.

The units for the drift file are "PPM", or "parts per million". Your clock will drift due to fluctuations in the frequency oscillating the quartz crystal on your motherboard. A fluctuation of just 0.001% (0.00001, or 10 PPM) means losing or gaining about 1 second per day. NTP has finer grained control than that, so we look at errors of margin using 0.0001% (0.000001, or 1 PPM). Thus:

• 1 PPM = 1 part per million = 1 microsecond per second = 3.6ms per hour = 86.4ms per day

Thus, my drift file shows the value of "2.643" which means my clock is off by 2.643 parts per million, which means it's currently off at 228.3552ms per day.

Solution 2:

According to the web site https://groups.google.com/forum/m/?fromgroups#!topic/comp.protocols.time.ntp/coDks98gw0U the value is a calculationn made per poll and needs to be divided by 4096 to get the actual drift value in milliseconds