10-10-2012
A service answers inquiries, but I believe it usually takes a daemon to actually maintain the local clock. In a sense, what is called an NTP client is often an ntp server, which can be configured to not share the time of day (but why bother?) Being a service to return time of day can be just passive settings, but usually being ntp syncronized requires a daemon. I suppose you could make it run under cron, not all the time mostly sleeping.
Usually, you point all internal hosts at a couple firewalls that get time from the big bad internet. You have backup, and a local standard. If you canin ntp unnecessarily, the clocks at the end of longer chains have more variance, possibly objctionable.
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LEARN ABOUT OSF1
ntp.drift
ntp.drift(4) Kernel Interfaces Manual ntp.drift(4)
NAME
ntp.drift - Network Time Protocol (NTP) drift file
DESCRIPTION
When the NTP daemon (xntpd) is first started, it computes the error in the intrinsic frequency of the clock on the computer it is running
on. This process usually takes about a day or two after the daemon is started to compute a good estimate of this (and it needs a good
estimate to synchronize closely to its server). Once the initial value is computed, it will change only by relatively small amounts during
the course of continued operation.
The driftfile declaration should always be included in the ntp.conf file. This provides xntpd with complete path name to a file in which
it can store the current value of the frequency error. That way, if the daemon is stopped and restarted, it can reinitialize itself to the
previous estimate without spending time recomputing the frequency estimate.
The ntp.drift file contains one line with the following format: freq_offset flag Specifies the nominal frequency offset. DO NOT modify
this field. Specifies the method used to improve system clock accuracy. Specifies that xntpd runs a Phase-Locked Loop (PLL) algorithm to
keep synchronized with other hosts. This is the default. Specifies the use of the PLL algorithm in the kernel. This requires the
NTP_TIME kernel option. After the option is configured in the kernel, edit the ntp.drift file and change the flag value to 1.
See System Administration for information on the NTP_TIME kernel option.
FILES
Conventional name of the drift file
RELATED INFORMATION
Commands: ntpdate(8), ntpq(8), xntpd(8), xntpdc(8)
Files: ntp.conf(4)
Network Administration, System Administration delim off
ntp.drift(4)