This question has come up a number of times in a localized way, this question is meant to provide the preferred/best method for synchronizing a system's clock using NTP.
The solution should handle multiple issues correctly, such as:
Correct for time at boot-up quickly where the clock has a large skew.
Provide a configuration that guards and/or corrects for situations where the clock can sometimes develop a large skew over time.
A robust solution that can handle and sync the time quickly when certain problems arise such as: "the time server wasn't accessible during boot" or "the internet is inaccessible during boot".
The ideal solution would be a single NTP configuration file that is able to handle all this.
Many of the pieces that will provide the "ultimate" solution are spread across the U&L site in questions such as these:
- How to force the time and date settings to refresh from the internet?
- Time synchronization of machines on LAN to GPS NTP server on the LAN
- How can I make a Puppet module that fixes time?
- NTP not syncing in a VM
There are bound to be others but these are the ones that I've seen that come to mind as being relevant.