Installing and Administering Internet Services

Chapter 7 315
Configuring the Network Time Protocol (NTP)
Troubleshooting ntp
No Server Suitable for synchronization found.
This message indicates that the NTP server is not responding for some
reason. Packets were sent out, but no reply was returned. Perhaps the
server is down, or the network link is broken or extremely congested. Or
perhaps the NTP daemon died on the server and has not yet locked on to
its time sources. NTP version 3.5 and above take between 5 and 15
minutes after starting up the daemon to synchronize, and it will not
respond to client requests during this time.
Last adjustment did not complete.
This message means that NTP is trying to make many adjustment
bigger than the system’s maximum slew rate allows in one clock tick. So
the remainder of the adjustments is pushed to the next clock tick. This is
handled automatically. You will often see this message in the first hour
after the NTP daemon is started. If you continue to see it after a few days
of steady operation, then your system clock is probably drifting causing
you to lose contact with your network time servers.
Synchronization lost.
This message indicates that NTP has cleared all of the statistics
registers and has started evaluating all available time servers and
choosing the “best” one. This message appears whenever a step
adjustment (greater than 128 milliseconds) is made, since thestep leaves
the system unsynchronized by definition. If your system is making a lot
of step adjustments, it probably means that you have network congestion
problems. To review this, do the following:
1. Run ntpq -p
2. Examine the dispersion statistics.
Common Problems
This section covers typical problems with ntp operation.
Problem 1: No suitable server for synchronization found.
Every NTP time hierarchy must have at least one stratum-1 server, with
an external time source configured, either an attached radio clock
(Netclock/2 WWVB Synchronized Clock) or the local system clock. If
there is no stratum-1 server in the hierarchy, no associations will be
formed. To verify that the localxntpd is able to form an association, issue