Network Time Protocol (NTP) is a protocol to synchronize a computer's system clock with a remote server. The remote time server can be another server on your local network or one of the publically accessible NTP servers.
Click here for a list of public NTP servers.
NTP in Linux is implemented by the ntpd daemon. This article demonstrates how to configure ntpd on Centos / RHEL 6.
1. Install ntpd
Install ntpd if it's not installed already
# yum install ntp
2. Edit configuration
Save the original ntp.conf file.
# mv /etc/ntp.conf /etc/ntp.conf.original
Create a new ntp.conf file which contains the following minimal configuration parameters
# Set the NTP server name or IP address. (Replace xxx.xxx.xxx.xxx with the NTP server address) server xxx.xxx.xxx.xxx # Set default access restriction restrict default limited kod nomodify notrap nopeer # Allow unrestricted access from localhost restrict 127.0.0.1 # Allow access on a subnet (Replace xxx.xxx.xxx.0 with your network address) restrict xxx.xxx.xxx.0 mask 255.255.255.0 nomodify notrap nopeer # The restrict access on IPv6 connections. # This is required only if you have IPv6 enabled in your system restrict -6 default kod nomodify notrap nopeer noquery restrict -6 ::1 # Drift file contains the exact drifting of your local clock from the time server. driftfile /var/lib/ntp/drift
3. Restart ntpd service
# service ntpd restart
4. Enable ntpd on boot
# chkconfig ntpd on
6. View ntp status
Run any of the following commands
# ntpq -p # ntpstat # ntpdc -c sysinfo
