Datasheet

“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 526 — #552

After completing all of the conﬁguration steps, close the dialog with ‘Ok’.

The server is now started with its new conﬁguration.

21.11.7 For More Information

For more information, the page of the Internet Software Consortium on

the subject (http://www.isc.org/products/DHCP/) is a good

source about the details of DHCP, including about version 3 of the pro-

tocol, currently in beta testing. Apart from that, you can always rely

on the man pages for further help. Try man dhcpd, man dhcpd.conf,

man dhcpd.leases, and man dhcp-options.

21.12 Time Synchronization with xntp

The exact time plays an important role in many processes in a computer

system. For this purpose, computers usually have a built-in clock. Unfortu-

nately, these clocks often do not meet the requirements of applications like

databases. Therefore, the local clock must regularly be corrected manually

or over a network. In the best case, the computer clock should never be set

back and the amount by which it is set forward should not exceed certain

time intervals. The computer clock can easily be corrected with ntpdate

from time to time. However, this causes a sudden time difference that may

not be tolerated by all applications.

xntp provides an interesting approach for solving this problems. First, xntp

regularly corrects the local computer clock on the basis of collected correc-

tion data. Second, it continuously corrects the local time with the help of

time servers in the network. Third, it enables the management of local ref-

erence clocks, such as radio-controlled clocks.

21.12.1 Conﬁguration in the Network

xntp is preset to use the local computer clock as time reference. The easi-

est way to use a time server in the network is to set “server” parameters.

For example, if a time server called ntp.example.com is available in the

network, this server can be added to the ﬁle /etc/ntp.conf in the form

server ntp.example.com.

526 21.12. Time Synchronization with xntp