Section 13.1. The Importance of Time

13.1. The Importance of Time

Without having the time accurately set on your machine, it's pretty hard to schedule tasks. Using the Date & Time preference panel (System Preferences Date & Time), you can set the time and date on your computer, as shown in Figure 13-1. However, if youre using a broadband connection or otherwise spend any amount of time connected to the Internet, you can have your computer set the date and time using a network time server.

A network time server is nothing more than a machine that has an accurate clock and that understands the Network Time Protocol (NTP). NTP is designed to keep large numbers of machines synchronized with an accurate clock. Apple ships Mac OS X with the addresses of their own NTP servers. Apple has servers for the Americas, Asia, and Europe.

In some network environments, you might find an NTP server locally. If you're using Mac OS X Server on your network, it includes an NTP server. Also, many Unix administrators have set up NTP servers for their local network. Finally, there are many publicly accessible NTP servers on the Internet; you can find a list of them at http://ntp.isc.org/bin/view/Servers/WebHome.

To take advantage of an NTP server, enable the "Set date & time automatically" checkbox in the Date & Time preferences and either select one of Apple's servers or

Figure 13-1. The Date & Time preference panel

enter the address information for another NTP server. When you set up a time server, the system does the following:

• Sets the time server that is being used in /etc/ntp.conf.

• Makes sure that the ntpd process is running. This process checks the time server periodically to make sure your clock is set correctly.

• Sets the TIMESYNC line in /etc/hostconfig to -YES-, ensuring that ntpd starts when the system reboots.