NTP

Network Time Protocol

Software

ntpq

Understanding ntpq output

Query status:

ntpq -p
     

Jitter: variance in latency on the network Offset: time difference between the peers or between the server and client

Which one on which OS

Centos 8

chronyd

Ubuntu 20

timedated and friends: https://ubuntu.com/server/docs/network-ntp

HOWTO

Check ntp server

ntpdate -q ntp.server.name

FAQ

ntpd off by 10 minutes

try

ntpdate -b

ntpdate[26875]: no servers can be used, exiting

something is wrong :)

systemd ntp equivalent

timedatectl status

or

systemctl status systemd-timesyncd.service