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
0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *

10 + 4 =