Knowledgebase

Its name is fairly self-explanatory — the Network Time Protocol is a protocol used to synchronize internal clock times on computers in a network. This applies to synchronizing clock times with a server on the Internet, as well as synchronizing machines on a local network. It’s typically used in a client-server configuration, but also supports peer-to-peer time synchronization. NTP is used to sync to Coordinated Universal Time (UTC), while timezone management is handled by the operating system. Keeping correct time is particularly important for logging, networking, and even more so on clustered and distributed computer systems. 

Now, we can’t really install a protocol but what we will actually be installing is the NTP daemon, or ntpd. Daemons are operating system programs that run in the background without needing any intervention. While computers are very intelligent, they are still just machines which are subject to small fluctuations in the electronic components. This can cause a time drift . A time drift is a small inconsistency in timekeeping. The NTP daemon will handle clock time syncing automatically by querying an NTP server at regular time intervals to correct those discrepancies. 

yum install -y ntp

systemctl start ntp 

systemctl enable ntpd 

systemctl status ntpd ntpdate -u -s 0.centos.pool.ntp.org 1.centos.pool.ntp.org 2.centos.pool.ntp.org 

systemctl restart ntpd 

timedatectl hwclock -w 


Add crontab to update after reboot 

crontab -e

add the following line and save

@reboot /usr/sbin/ntpdate -b -s -u 1.asia.pool.ntp.org 

ntpdate -u -s 1.asia.pool.ntp.org