The driftfile statement specifies the file containing the precision drift of the local oscillator. This value is used by the local ntpd daemon to calculate an adjustment for local frequency fluctuations.
The drift file is specified in the start/stop script (in <instdir>/etc/rc.d) as command line parameter of the NTP daemon. As specifications on the command line override configuration file specifications, the driftfile statement is normally ignored, see also Startup options of the NTP daemon ntpd .
driftfile filename
filename
Specifies the file containing the precision drift of the local oscillator. The file is updated by the current drift value being written to a temporary file which is then renamed to replace the old file. The ntpd therefore requires write authorization for the directory containing the file, and you should avoid file links.
If the filename file or the driftfile statement does not exist, the drift is initially assumed to be 0. The local NTP daemon ntpd then calculates the drift and saves it as a floating-point value in multiples of 10-6 (parts per million, ppm). This saved value is used with a restart.