How does synchronize time - CentOS

Environment

• CentOS x64

Content
Install NTP

#yum install ntp

Set ntpd service

#/sbin/chkconfig ntpd on

Set it to synchronize time with Hong Kong Observatory

#vim /etc/ntp.conf
server stdtime.gov.hk

Synchronize time with Hong Kong Observatory

#/usr/sbin/ntpdate stdtime.gov.hk

Start ntpd service

#/sbin/service ntpd start

Firewall:

iptables -A OUTPUT -p udp --dport 123 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -p udp --sport 123 -m state --state ESTABLISHED -j ACCEPT

Not set the IP Address as:

stdtime.gov.hk: 118.143.17.82, 118.103.146.184

If set, have "ntpdate[20014]: no server suitable for synchronization found"

Appendix: CentOS7

timedatectl set-timezone Asia/Hong_Kong

timedatectl

hwclock -r

Reference

• Using NTP to sync time on CentOS

Update

• +Appendix: CentOS7 @2019-Aug-15