The Sysadmins Daily Grind: OpenNTPD
On vacation we may be happy just to check the position of the sun,but computers need a more accurate measure of time. Luckily, there are atomic clocks that can receive time signals by radio and off the Internet.
I’m a practical person, and also a big believer in being punctual. Of course, I expect my servers to keep perfect time. Half a minute can make all the difference between a happy admin and a chaotic network. Just as an example, imagine someone sends me an email message. The first thing that happens is that the spam filter gets to check the message, which it then hands over to the anti-virus server. If the AV server is happy with the message, the next step along the way is the mail hub, which locates the correct mail server and forwards the message to that location, where the mail server finally dumps the message in my inbox. In other words, email messages on my network are handled by no less than four servers. If there is a problem, I check the logfiles to see where things are going wrong. And this is where precise timekeeping becomes imperative.