In this post, i will show you on how to configure NTP server for time adjustment. NTP, Network Time Protocol, it is an Internet protocol used to synchronize the clocks of computers or servers to some NTP server on internet or intranet.
Install the following package using yum :
[root@centos62 ~]# yum install ntp -y Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: centos.maulvi.net * extras: centos.maulvi.net * updates: centos.maulvi.net Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package ntp.i686 0:4.2.4p8-2.el6.centos will be installed --> Finished Dependency Resolution Dependencies Resolved ==================================================================================================== Package Arch Version Repository Size ==================================================================================================== Installing: ntp i686 4.2.4p8-2.el6.centos CentOS6.2-Repository 436 k Transaction Summary ==================================================================================================== Install 1 Package(s) Total download size: 436 k Installed size: 1.1 M Downloading Packages: Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : ntp-4.2.4p8-2.el6.centos.i686 1/1 Installed: ntp.i686 0:4.2.4p8-2.el6.centos Complete!
Once NTP is installed you need to update the configuration file, ntp.conf located in the /etc directory :
[root@centos62 ~]# vi /etc/ntp.conf
# For more information about this file, see the man pages # ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5). driftfile /var/lib/ntp/drift # 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 192.168.1.0 mask 255.255.255.0 nomodify notrap # 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 #broadcast 192.168.1.255 autokey # broadcast server #broadcastclient # broadcast client #broadcast 224.0.1.1 autokey # multicast server #multicastclient 224.0.1.1 # multicast client #manycastserver 239.255.254.254 # manycast server #manycastclient 239.255.254.254 autokey # 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 # Enable public key cryptography. #crypto includefile /etc/ntp/crypto/pw # Key file containing the keys and key identifiers used when operating # with symmetric key cryptography. keys /etc/ntp/keys # Specify the key identifiers which are trusted. #trustedkey 4 8 42 # Specify the key identifier to use with the ntpdc utility. #requestkey 8 # Specify the key identifier to use with the ntpq utility. #controlkey 8 # Enable writing of statistics records. #statistics clockstats cryptostats loopstats peerstats
Start the NTP service :
[root@centos62 ~]# /etc/rc.d/init.d/ntpd start Starting ntpd: [ OK ]
Set NTP service start at boot :
[root@centos62 ~]# chkconfig ntpd on
[root@centos62 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
113.23.142.94 202.71.100.89 5 u 33 64 1 55.809 35573.8 0.001
enterprise.wyne 203.129.68.14 3 u 32 64 1 55.888 35592.2 0.001
202.71.100.89 124.82.204.2 4 u 31 64 1 54.479 35584.8 0.001
To verify the NTP service is now running on the server using the following command :
[root@centos62 ~]# ps -ef | grep ntpd ntp 22682 1 0 22:38 ? 00:00:00 ntpd -u ntp:ntp -p /var/run/ntpd.pid -g root 22696 2377 0 22:40 pts/0 00:00:00 grep ntpd
The command should return two lines showing that the ntpd process is running and the ntpd grep process you executed
[root@centos62 ~]# service ntpd status ntpd (pid 22682) is running...
[root@centos62 ~]# watch ntpq -c lpee
Every 2.0s: ntpq -c lpee Tue Feb 7 23:00:24 2012
remote refid st t when poll reach delay offset jitter
==============================================================================
ns2.epiweb.com. .RMOT. 16 u - 64 0 0.000 0.000 0.000
zephyr.vtsv.com .INIT. 16 u - 64 0 0.000 0.000 0.000
