How to configure NTP Server in RedHat / CentOS / Fedora
Introduction
Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. NTP is a protocol designed to synchronize the clocks of computers over a network.
By Default Port # 123
Step 1: Install ntp Package
To configure NTP Server, firstly we need to install the ntp package:
# yum -y install ntp Loaded plugins: amazon-id, rhui-lb Resolving Dependencies --> Running transaction check ---> Package ntp.x86_64 0:4.2.6p5-19.el7_0 will be installed --> Processing Dependency: ntpdate = 4.2.6p5-19.el7_0 for package: ntp-4.2.6p5-19.el7_0.x86_64 --> Processing Dependency: libopts.so.25()(64bit) for package: ntp-4.2.6p5-19.el7_0.x86_64 --> Running transaction check ---> Package autogen-libopts.x86_64 0:5.18-5.el7 will be installed ---> Package ntpdate.x86_64 0:4.2.6p5-19.el7_0 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================================================ Package Arch Version Repository Size ================================================================================================================ Installing: ntp x86_64 4.2.6p5-19.el7_0 rhui-REGION-rhel-server-releases 540 k Installing for dependencies: autogen-libopts x86_64 5.18-5.el7 rhui-REGION-rhel-server-releases 66 k ntpdate x86_64 4.2.6p5-19.el7_0 rhui-REGION-rhel-server-releases 82 k Transaction Summary ================================================================================================================ Install 1 Package (+2 Dependent packages) Total download size: 689 k Installed size: 1.6 M Downloading packages: (1/3): autogen-libopts-5.18-5.el7.x86_64.rpm | 66 kB 00:00:00 (2/3): ntp-4.2.6p5-19.el7_0.x86_64.rpm | 540 kB 00:00:00 (3/3): ntpdate-4.2.6p5-19.el7_0.x86_64.rpm | 82 kB 00:00:00 ---------------------------------------------------------------------------------------------------------------- Total 1.3 MB/s | 689 kB 00:00:00 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : ntpdate-4.2.6p5-19.el7_0.x86_64 1/3 Installing : autogen-libopts-5.18-5.el7.x86_64 2/3 Installing : ntp-4.2.6p5-19.el7_0.x86_64 3/3 Verifying : autogen-libopts-5.18-5.el7.x86_64 1/3 Verifying : ntp-4.2.6p5-19.el7_0.x86_64 2/3 Verifying : ntpdate-4.2.6p5-19.el7_0.x86_64 3/3 Installed: ntp.x86_64 0:4.2.6p5-19.el7_0 Dependency Installed: autogen-libopts.x86_64 0:5.18-5.el7 ntpdate.x86_64 0:4.2.6p5-19.el7_0
Step 2: Configuration
Make changes in ntp.conf file
# vi /etc/ntp.conf restrict 10.0.0.0 mask 255.255.255.0 nomodify notrap server 0.rhel.pool.ntp.org iburst server 1.rhel.pool.ntp.org iburst server 2.rhel.pool.ntp.org iburst server 3.rhel.pool.ntp.org iburst
Now start the ntpd service
# /etc/rc.d/init.d/ntpd start Starting ntpd: [ OK ]
Enable ntpd in multi-user levels.
# chkconfig ntpd on
To verify NTP peers synchronization status, delay, offset, jitter use the following command:
# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== *natasha.netwurx 209.242.224.11 2 u - 64 1 67.464 6.336 0.038 static-72-87-88 192.5.41.209 2 u 1 64 1 89.650 -3.463 0.000 96.44.142.5 204.123.2.5 2 u - 64 1 56.794 0.794 0.000 ns.tx.primate.n .INIT. 16 u - 64 0 0.000 0.000 0.000