This is a quick and dirty cheatsheet on both the old NTP and the newer Chrony time protocols.
I am presuming that NTP is being used by RHEL6 and thus some of the command (starting/stopping) use the old RHEL 6 services, chkconfig, etc, if not then subsitute for the newer systemctl command.
| files and directories | /etc/ntp.conf /etc/ntp |
| daemons | ntpd |
| configuration | chkconfig ntpd on # runlevel 2,3,4 and 5 chkconfig --list ntpd edit /etc/ntp.conf |
| starting/stopping/status | service ntpd start service ntpd stop service ntpd status |
| displaying | ntpq -p ntptime ntpdate ntpstat ntpdc # NTP commandline console |
| firewall | iptables -A OUTPUT -p udp --dport 123 -j ACCEPT iptables -A INPUT -p udp --sport 123 -j ACCEPT |
I am presuming that Chrony is being used by RHEL 7 and 8 and thus some of the command (starting/stopping) use the newer systemctl command.
| files and directories | /etc/chrony.conf /etc/chrony.key |
| daemons | chronyd |
| configuration | edit /etc/chrony.conf systemctl enable chronyd systemctl disable chronyd |
| starting/stopping/status | systemctl start chronyd systemctl stop chronyd systemctl status chronyd |
| displaying | chronyc sources [-v] chronyc tracking chronyc sourcestats |
| firewall | firewall-cmd --permanent --zone=public --add-port=123/udp |