4.9. NTP

NTP (Network Time Protocol) is used to synchronize the clocks of computer systems over the network. In Red Hat Enterprise Linux 6, the default configuration file, /etc/ntp.conf, now has the following lines commented:

#server 127.127.1.0 # local clock
#fudge 127.127.1.0 stratum 10

#server 127.127.1.0 # local clock
#fudge 127.127.1.0 stratum 10

This configuration means that ntpd will only distribute time information to network clients if it is specifically synchronized to an NTP server or a reference clock. To get ntpd to offer this information even when not synchronized, the two lines must be uncommented.

Also, when ntpd is started with the -x option (in OPTIONS in the /etc/sysconfig/ntpd file), or if there are servers specified in /etc/ntp/step-tickers, the service no longer runs the ntpdate command before starting. There is now a separate ntpdate service which can be enabled independently from the ntpd service. This ntpdate service is disabled by default, and is only recommended for use when other services require the correct time before starting, or do not function properly when time modifications occur later by ntpd.

If you encounter problems running this service with the default NetworkManager configuration, a possible fix is to add NETWORKWAIT=1 to /etc/sysconfig/network, as described in the Red Hat Enterprise Linux Deployment Guide.

As of Red Hat Enterprise Linux 6.5, the format used by ntpd for syslog messages has changed. This affects users attempting to parse these log messages. Additionally, users can now configure the types of message to be logged using the logconfig option in ntp.conf.