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
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Package Arch Version Repository Size
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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
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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
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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
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*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