How to Setup NTP Server on CentOS/RHEL 7/6 and Fedora 27/26

We have running approximate 50 systems on our LAN. In which most of the systems are running with Linux operating system’s and few of them are running with Windows and MAC. In this setup, we will configure one of Linux system as NTP server which will be synchronized from public NTP server. Now remaining system’s on LAN will sync their time from local LAN NTP server.

Step 1 – Install NTP Server

NTP packages are available under default repositories. You just log in to your server as root user and execute the following command.

yum install ntp     ## CentOS/RHEL systems 
dnf install ntp     ## Fedpra systems 

Step 2 – Setup NTP Server

Sync Local Time from pool.ntp.org

First we need to keep synchronize the time on this server. For this, we will use NTP POOL cluster servers to synchronize the time of the local system. NTP POOL project is providing a large number of cluster servers. Let’s edit NTP configuration file and update following values

vim /etc/ntp.conf

server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst

As NTP pool providing a large number of server spread worldwide. We suggest using any nearby servers also. You can find nearby servers at http://www.pool.ntp.org/en/.

Allow LAN Systems

Now configure your NTP server to allow LAN systems to keep synchronize their time from this server. To do it add following entry in configuration file

 restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

Step 3 – Restart NTP Server

NTP server listen on UDP port 123. After making all above configuration, Let’s restart NTP server using following commands.

For CentOS/RHEL 7 and Fedora

systemctl start ntpd
systemctl enable ntpd

For CentOS/RHEL 6/5

service ntpd start
chkconfig ntpd on