[Oracle DataBase Server 12.1 Installation on Oracle Linux 6.7]: Configuring Time Synchronization Services

Specify available ntp servers

# vi /etc/ntp.conf

For example:

server 0.rhel.pool.ntp.org
server 1.rhel.pool.ntp.org
server 2.rhel.pool.ntp.org

You need to make changes to the ntpd parameter file

# vi /etc/sysconfig/ntpd

replace

# Drop root to id 'ntp:ntp' by default.
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"

with

# Drop root to id 'ntp:ntp' by default.
# OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"
OPTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"

# service ntpd restart