install

apt install ntp

sample config specify ntp server at server

$ grep -E -v "^#|^$" /etc/ntp.conf
driftfile /var/lib/ntp/ntp.drift
leapfile /usr/share/zoneinfo/leap-seconds.list
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
server 192.168.xxx.xxx iburst
restrict -4 default ignore
restrict -6 default ignore
restrict 127.0.0.1
restrict ::1

reload configuration

systemctl status ntp
journalctl -u ntp -f
systemctl force-reload ntp

confirm commands

ntpq -pn
ntpq -c readlist

server

For server settings, at lease a restrict <client address> line to allow ntp clients access. If you don't add noquery, you allow the client to query your ntpd status.

$ grep -E -v "^#|^$" /etc/ntp.conf
driftfile /var/lib/ntp/ntp.drift
leapfile /usr/share/zoneinfo/leap-seconds.list
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
server 192.168.xxx.xxx iburst
restrict -4 default ignore
restrict -6 default ignore
restrict 127.0.0.1
restrict ::1
restrict 192.168.xxx.xxx mask 255.255.255.0 nomodify notrap nopeer noquery

confirm commands

ntpq -pn <address>
ntpq -c readlist <address>