https://engineering.fb.com/2020/03/18/production-engineering/ntp-service/

https://cyberhost.uk/setup-chrony-server/

https://www.advtimesync.com/docs/manual/stratum1.html

https://gist.github.com/mutin-sa/eea1c396b1e610a2da1e5550d94b0453

sudo vi /etc/chrony/chrony.conf

server ntp-1.vt.edu iburst
server clock.nyc.he.net iburst
server time.apple.com iburst
server time.google.com iburst
server time-e-g.nist.gov iburst
server time-e-b.nist.gov iburst
server utcnist3.colorado.edu iburst
server navobs1.wustl.edu iburst
server time1.facebook.com iburst
server time2.facebook.com iburst
server time3.facebook.com iburst
server time4.facebook.com iburst
server time5.facebook.com iburst


systemctl status chronyd; systemctl daemon-reload ; systemctl restart chronyd;sleep 3; chronyc sources -v