If ntpd service failing to start, check the log file '/var/log/messages'.
If you are getting the below message, you can use the following steps to resolve the issue
... cap_set_proc() failed to drop root privileges: Operation not permitted
Open the file /etc/sysconfig/ntpd and comment out the following line.
# OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid -g"
Restart the ntpd service
# service ntpd restart