log in as root

--> ntpdate -u de.timeserver.pub

Open the /etc/ntp.conf file and add the NTP server

# /etc/ntp.conf
# Global NTP-Server
server de.timeserver.pub
server us.timeserver.pub
server us2.timeserver.pub
pool 1.pool.ntp.org
#restrict
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery
# Drift file
driftfile /etc/ntp/drift

--> service ntpd start