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

#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 should 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 should be used only when other services require the correct time before starting, or do not function properly when time modifications occur later by ntpd.

You may encounter problems running this service with the default NetworkManager configuration. It may be necessary to add NETWORKWAIT=1 to /etc/sysconfig/network, as described in the Red Hat Enterprise Linux Deployment Guide.