The Time and Date Properties tool allows you to change the system date and time, to configure the time zone used by the system, and to setup the Network Time Protocol (NTP) daemon to synchronize the system clock with a time server.
You must be running the X Window System and have root privileges. To start the application from the desktop, click the Main Menu Button and choose > System Settings > Date & Time, or type the command redhat-config-date at a shell prompt.
The first tabbed window that appears after starting the Time and Date Properties tool is for configuring the system date and time and the NTP daemon (ntpd).
Figure 18-1. Time and Date Properties
To change the date, use the arrows to the left and right of the month to change the month. Use the arrows to the left and right of the year to change the year, and click on the day of the week to change the day of the week. Changes will not take place until you click the OK button.
To change the time, use the up and down arrow buttons beside the Hour, Minute, and Second in the Time section. Changes will not take place until you click the OK button.
Changing the date and time will change the system clock as well as the hardware clock. Clicking Apply or OK is equivalent to executing the date and hwclock commands with the selected date and time.
The Network Time Protocol (ntpd) daemon synchronizes the system clock with a remote time server or time source (such as a satellite). The application allows you to configure a NTP daemon to synchronize your system clock with a remote server. To enable this feature, click the Enable Network Time Protocol button. This will enable the Server pull-down menu. You can then choose one of the predefined servers or type a server name in the pull-down menu. Your system will not start synchronizing with the NTP server until you click Apply. After you click Apply, the configuration will be saved and the NTP daemon will be started (or restarted if it is already running). If you want this daemon to start automatically at boot time, you need to execute the command /sbin/chkconfig --level 345 ntpd on to enable ntpd for runlevels 3, 4, and 5.
For more information on NTP, read the NTP documentation available in the /usr/share/doc/ntp-version directory.
The NTP server is written to the /etc/ntp.conf and /etc/ntp/step-tickers files.
Clicking the OK button will apply any changes that you have made to the date and time, the NTP daemon settings, and the time zone settings and then exit the program.
If you configured a medium or high security level during installation or with the Security Level Configuration Tool, the firewall rules will block the connection to the NTP port. To allow NTP to work, run the Security Level Configuration Tool, select Customize, and add udp:ntp to the other ports.