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A network time protocol server is important to keep everything in sync. For example, if one server takes Web-based orders, and a second server deals with inventory, it then becomes important that the servers are in sync to help customers know inventory in real time. Otherwise a customer who makes an order may be out of luck. If they order what they want even after a few seconds after the last item is ordered you'll then have to deal with unhappy customers. Network Time Protocol Servers are available worldwide to help all of us keep our systems and networks in sync. If synchronized time is important to you, it's best to find a central timeserver geographically close to you. A list of public NTP servers is available at www dot pool dot ntp dot org. Red Hat has several servers available for your use at the following urls: 0, 1 and 2 dot rhel dot pool dot ntp dot org. As of this writing they map to IP addresses located in the Northeastern United States. If you're in a different location, you may want to use a different NTP server from the www dot pool dot ntp dot org list. Just make sure it's a Stratum Two server and you have permission of the administrator. The process of configuring an NTP server on Red Hat Enterprise Linux 5 is straightforward. For now, let's check the status of the NTP daemon. The service is currently stopped and it doesn't set the start in any runlevel. The simplest way to configure an activated local NTP server is with the Date slash Time Properties tool, available with the sysconfig date command. The sysconfig time works just as well. This opens the date time properties tool and you'll want to click the network time protocol tab. If we enable the Network Time Protocol by default this looks at the Red Hat NTP servers. Of course, you can edit these to the NTP servers of your choice. Advanced options. The synchronize system clock before starting service option synchronizes the local system with one of the listed NTP servers as you boot Linux. The Use Local Time Source option allows you to synchronize your computer hardware clock with the clock on the NTP service. Just be warned before you activate an NTP client, if there's more than a few minutes of variance with the NTP server clock, NTP service won't work for that client. So, for example, if you're using VMware, and especially the snapshot function, the snapshot freezes that system in time. If you restore that snapshot more than a few minutes later, that client won't be able to use the NTP server to get back in sync with other clients on that network. Now that we've made our selections, we click OK, the tool contacts one or more of the NTP servers, it also configures a local NTP server, as we'll see momentarily. It may take a little bit of time as it may need to contact more than one server to assure proper time. And now, the NTP daemon is running. Not only that, the service is now set to run when you boot into runlevels 3 and 5. The NTP service is now configured. If you want to see the detailed configuration file, open the ntp dot conf file. One last bit, the NTP service is not affected by any SELinux settings.
| Course: | Red Hat Certified Engineer |
| Author: | Michael Jang |
| SKU: | 33845 |
| ISBN: | 1-934743-47-X |
| Release Date: | 2008-01-18 |
| Duration: | 6.5 hrs / 94 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |