Network Time Protocol is used to synchronize the time on your Linux system with a centralized NTP server.
A local NTP server on the network can be synchronized with an external timing source to keep all the servers in your organization in-sync with an accurate time.
Step 1: PreWork
Before install NTP server, check is the package is installed or not already by using rpm commend
[root@CentOS66x64 ~]# rpm -qa ntp
ntp-4.2.6p5-1.el6.centos.x86_64 à if you notice package is listing, skip step 2.
[root@CentOS66x64 ~]#
Step 2: NTP Installation
[root@foxutech ~]# yum install ntp
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
* base: centos.excellmedia.net
* extras: centos.excellmedia.net
* updates: centos.excellmedia.net
Setting up Install Process
Resolving Dependencies
–> Running transaction check
—> Package ntp.i386 0:4.2.2p1-18.el5.centos set to be updated
–> Finished Dependency Resolution
Dependencies Resolved
========================================================================================================================================================================
Package Arch Version Repository Size
========================================================================================================================================================================
Installing:
ntp i386 4.2.2p1-18.el5.centos updates 1.3 M
Transaction Summary
========================================================================================================================================================================
Install 1 Package(s)
Upgrade 0 Package(s)
Total download size: 1.3 M
Is this ok [y/N]: t
Is this ok [y/N]: y
Downloading Packages:
ntp-4.2.2p1-18.el5.centos.i386.rpm | 1.3 MB 00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : ntp 1/1
Installed:
ntp.i386 0:4.2.2p1-18.el5.centos
Complete!
Step 3: NTP Configuration
[root@foxutech ~]# vi /etc/ntp
ntp/ ntp.conf
[root@foxutech ~]# vi /etc/ntp.conf
[root@foxutech ~]# vi /etc/ntp.conf
# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery
# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1
restrict -6 ::1
# Hosts on local network are less restricted.
restrict x.x.x.x mask y.y.y.y nomodify notrap
server x.x.x.x
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 0.centos.pool.ntp.org
server 1.centos.pool.ntp.org
server 2.centos.pool.ntp.org
server 3.centos.pool.ntp.org
#broadcast 192.168.1.255 key 42 # broadcast server
#broadcastclient # broadcast client
#broadcast 224.0.1.1 key 42 # multicast server
#multicastclient 224.0.1.1 # multicast client
#manycastserver 239.255.254.254 # manycast server
#manycastclient 239.255.254.254 key 42 # manycast client
# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available.
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10
# Drift file. Put this in a directory which the daemon can write to.
# No symbolic links allowed, either, since the daemon updates the file
# by creating a temporary in the same directory and then rename()’ing
# it to the file.
driftfile /var/lib/ntp/drift
# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography.
keys /etc/ntp/keys
Step 4: Start and Check NTP
[root@foxutech ~]# chkconfig ntpd on
[root@foxutech ~]# /etc/init.d/ntpd start
Starting ntpd: [ OK ]
For checking :
[root@foxutech ~]# ntpq -p
[root@foxutech ~]# ntpdc -c sysinfo
[root@foxutech ~]# ntpdate –u 180.151.36.179
[root@foxutech ~]# date
Thu Jul 30 11:26:30 IST 2015