ntp(8) BSD System Manager's Manual ntp(8)NAME
ntpd, ntpdate, ntpdc, ntpq, ntptimeset, ntptrace, tickadj - Network Time
Protocol
DESCRIPTION
The complete documentation for the ntpd, ntpdate, ntpdc, ntpq,
ntptimeset, ntptrace, and tickadj commands from the NTP distribution is
only available in HTML form:
ntpd: file:///usr/share/doc/ntp/ntpd.htm
ntpdate: file:///usr/share/doc/ntp/ntpdate.htm
ntpdc: file:///usr/share/doc/ntp/ntpdc.htm
ntpq: file:///usr/share/doc/ntp/ntpq.htm
ntptimeset: file:///usr/share/doc/ntp/ntptime.htm
ntptrace: file:///usr/share/doc/ntp/ntptrace.htm
tickadj: file:///usr/share/doc/ntp/tickadj.htm
general: file:///usr/share/doc/ntp/index.htm
Use lynx(1) or netscape(1) to view these documents.
SEE ALSOdate(1), adjtime(2), getttimeofday(2).
BUGS
For security reasons, the system will not permit ntpdate to step the time
to an earlier time than the current time if the security level is greater
than zero. If the -b flag to ntpdate is not specified, it will always
use adjtime(2) to correct the time gradually. When the security level is
zero (for example, when in single user mode) the -b flag may be used to
force ntpdate to step the time backwards if necessary. Ntpd is aware of
this limitation and will only slew the time (see adjtime(2)).
When booting, if the file /etc/ntp.conf exists, rc(8) scans it for
``broadcastclient'', ``multicastclient'', ``peer'', and ``server'' key-
words. If any are found, it runs ntpdate with the -b flag to sync time
with the listed time servers. This will step the clock close to the cur-
rent time in single-user mode, which will allow ntpd to tune it more
finely when the system is in multi-user mode.
Ntpd is only able to compensate for a system clock that has an error of
less than 100PPM (about .01%). For clocks with an error greater than
this, the kernel tick variable will need to be adjusted from /etc/rc us-
ing the tickadj command. The procedure for doing this is documented in
the ``Dealing with Frequency Tolerance Violations'' section of ``"Notes
on Configuring NTP and Setting up a NTP Subnet"'' in the HTML documenta-
tion referred to above. Note that the tickadj command should not be used
to set the tickadj kernel variable.
BSDI BSD/OS October 20, 1999 1