Setting Up A Local Reference Clock - Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 04-08-2006 Installation Manual

its name to the file /etc/ntp.conf by adding the line server
ntp.example.com. To add more time servers, insert additional lines with the key-
word server. After initializing xntpd with the command rcntpd start, it takes
about one hour until the time is stabilized and the drift file for correcting the local
computer clock is created. With the drift file, the systematic error of the hardware clock
can be computed as soon as the computer is powered on. The correction is used imme-
diately, resulting in a higher stability of the system time.
There are two possible ways to use the NTP mechanism as a client: First, the client can
query the time from a known server in regular intervals. With many clients, this approach
can cause a high load on the server. Second, the client can wait for NTP broadcasts sent
out by broadcast time servers in the network. This approach has the disadvantage that
the quality of the server is unknown and a server sending out wrong information can
cause severe problems.
If the time is obtained via broadcast, you do not need the server name. In this case, enter
the line broadcastclient in the configuration file /etc/ntp.conf. To use one
or more known time servers exclusively, enter their names in the line starting with
servers.
33.3 Setting Up a Local Reference
Clock
The software package xntp contains drivers for connecting local reference clocks. A
list of supported clocks is available in the xntp-doc package in the file /usr/
share/doc/packages/xntp-doc/html/refclock.htm. Every driver is
associated with a number. In xntp, the actual configuration takes place by means of
pseudo IPs. The clocks are entered in the file /etc/ntp.conf as though they existed
in the network. For this purpose, they are assigned special IP addresses in the form
127.127.t.u. Here, t stands for the type of the clock and determines which driver
is used and u for unit, which determines the interface used.
Normally, the individual drivers have special parameters that describe configuration
details. The file /usr/share/doc/packages/xntp-doc/html/driverNN
.htm (where NN is the number of the driver) provides information about the particular
type of clock. For example, the "type 8" clock (radio clock over serial interface) requires
an additional mode that specifies the clock more precisely. The Conrad DCF77 receiver
Time Synchronization with NTP 627