ntp client configuration

NTP Server/client Configuration

1. Install the required ntp package on the server.

# yum install ntp

2. Ensure the following entries are in ntp configuration file /etc/ntp.conf.

# cat /etc/ntp.conf

restrict default kod nomodify notrap nopeer noquery

restrict -6 default kod nomodify notrap nopeer noquery

restrict 127.0.0.1

restrict -6 ::1

server 0.pool.ntp.org

server 1.pool.ntp.org

server 2.pool.ntp.org

server 3.pool.ntp.org

restrict 10.10.10.0 mask 255.255.255.0 nomodify notrap

driftfile /var/lib/ntp/drift

keys /etc/ntp/keys

 ------------ 

 For sync with NTP server 

 /usr/sbin/ntpdate 10.11.X.X 

In the /etc/ntp.conf file you will have to mention the NTP server(s) in your environment.

3. Now you can start the ntpd service.
For RHEL 5,6:

# service ntpd start

For RHEL 7:

# systemctl start ntpd.service

NTP Client/ RHEL 5,6/ RHEL 7Configuration

1. For client NTP configuration, add the below configuration in the /etc/ntp.conf file.

# cat /etc/ntp.conf

restrict default kod nomodify notrap nopeer noquery

restrict -6 default kod nomodify notrap nopeer noquery

restrict 127.0.0.1

restrict -6 ::1

server ntp.server.com

driftfile /var/lib/ntp/drift

keys /etc/ntp/keys

Here, ntp.server.com is the server you configured as NTP server in the example shown at the start of the post. There can be multiple NTP servers for redundancy purpose. Add a new line for each of the NTP servers in the /etc/ntp.conf file.

2. Start the ntpd service on the ntp client server.
For RHEL 5,6:

# service ntpd start

For RHEL 7:

# systemctl start ntpd.service

# systemctl enable ntpd