NTP Server Setup in CentOS
NTP – is a protocol used in Transport Layer which runs over port 123 UDP. NTP allows you automatically sync your system time with a remote server. Keeping your system’s date and time accurate with the use of NTP. Your machine’s time will sync with the servers that are known to have accurate time. While time is passing by, the internal clock of computer slowly drifts away from a perfectly accurate setting. The accurate time in machine will helps when you need to check the logs from a particular time of day.
Install and Configure NTP
Installation of NTP
Debian/Ubuntu
# sudo aptitude update
# sudo aptitude install ntp
Centos
# sudo yum install ntp
After the installation, you can check the service will run at boot time by running:
# sudo /sbin/chkconfig ntpd on
Fedora/Rhel
# sudo yum install ntp
After the installation, you can check the service will run at boot time by running:
# sudo chkconfig ntpd on
Service Starting
Make sure that NTP is running fine after the installation.
# sudo /etc/init.d/ntp start
You can stop or restart the NTP service by running the following command
# sudo /etc/init.d/ntp stop
# sudo /etc/init.d/ntp restart
Once the installation has completed, go to official NTP Public Pool Time Servers, select your continent area where the server physically is located, then search for your country location and a list of NTP servers should appear.
Edit the NTP daemon main configuration file /etc/ntp.conf comment the default list of Public Servers from pool.ntp.org project and replace it with the list provided by your country
For example,
#sever 0.centos.pool.ntp.org iburst
# sever 1.centos.pool.ntp.org iburst
Add like this,
server 0.ro.pool.ntp.org iburst
server 1.ro.pool.ntp.org iburst
If you need to allow clients from your networks to synchronize time with this server. You should make the changes in the NTP configuration like as given below:
restrict 192.168.1.0 netmask 255.255.255.0 nomodify notrap
The nomodify notrap means, your clients are not allowed to configure the server
Adding Firewall Rules
You can add firewall rule by using the following line:
# firewall-cmd –add-service=ntp –permanent
To obtain the effect of firewall rule you should reload the rule.
# firewall-cmd –reload
Start the NTP server
# systemctl start ntpd
# systemctl enable ntpd
Check the status of NTP service
# systemctl status ntpd
Verify the Time sync of server
Execute the following commands to verify NTP peers sync status and your system time.
# ntpq -p
# date –R
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