What we need to install and configure is a NTP client that will connect to a list of possible NTP servers. The preferred server is npt.ensieta.ecole on the LAN (Local Area Network).
First we install ntpdate and npt client
sudo apt install ntpdate ntp
The we have to put the IP address of the NTP server by adding the folliwin line in /etc/hosts.
192.168.45.227 NTP-server-host
If you do not know the NTP server's IP, type :
ping -c 1 ntp PING c4510r-227.ensieta.ecole (192.168.45.227) 56(84) bytes of data. 64 bytes from NTP-server-host (192.168.45.227): icmp_seq=1 ttl=255 time=1.34 ms
The server must be added in the ntp configuration file /etc/ntp.conf. Add the following line at the end of the /etc/conf :
server ntp.ensieta.ecole iburst
Note that ensieta.ecole here is the domain name of the LAN.
Then restart the NTP client service :
sudo service ntp restart
You can check if all is working by display the NTP queue:
ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== 0.ubuntu.pool.n .POOL. 16 p - 64 0 0.000 0.000 0.000 1.ubuntu.pool.n .POOL. 16 p - 64 0 0.000 0.000 0.000 2.ubuntu.pool.n .POOL. 16 p - 64 0 0.000 0.000 0.000 3.ubuntu.pool.n .POOL. 16 p - 64 0 0.000 0.000 0.000 ntp.ubuntu.com .POOL. 16 p - 64 0 0.000 0.000 0.000 *NTP-server-host 192.168.1.6 4 u 15 64 1 1.475 0.738 2.015
Note that the actual NTP server IP address is 192.168.1.6
Info taken from : https://vitux.com/how-to-install-ntp-server-and-client-on-ubuntu/