How to Setup NTP Server on CentOS/RHEL 7/6/5 and Fedora 21/20/19

Setup Details

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 sever which will be synchronized from public NTP server. Now remaining system’s on LAN will sync their time from local LAN NTP server.

Installing NTP Server

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

# yum install ntp

Configure NTP Server

Sync Local Time from pool.ntp.org

First we need to keep synchronize time of this server. For this we will use NTP POOL cluster servers to synchronize time of local system. NTP POOL project is providing large number of cluster servers. Lets 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 large number of server spread world-wide. We suggest to use any near by 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

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 21

# systemctl start ntpd
# systemctl enable ntpd

For CentOS/RHEL 6/5 and Fedora 20/19

# service ntpd start
# chkconfig ntpd on