ntpoffline

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Server

server side configuration:

# yum install -y ntpd
# vim /etc/ntpd.conf

The configuration file is listed as following:

driftfile /var/lib/ntp/drift
restrict default nomodify notrap nopeer noquery
restrict 127.0.0.1 
restrict ::1
restrict 192.168.0.0 mask 255.255.0.0 nomodify notrap
server 127.127.1.0  # local clock
fudge 127.127.1.0  stratum 10
includefile /etc/ntp/crypto/pw
keys /etc/ntp/keys
disable monitor

Disable the chronyd service thus the ntpd could acts properly:

# systemctl disable chronyd
# systemctl enable ntpd
# systemctl start ntpd
# systemctl disable firewalld

Client

Install via:

# yum install -y ntpd

Configuration file:

driftfile /var/lib/ntp/drift
restrict default nomodify notrap nopeer noquery
restrict 127.0.0.1 
restrict ::1
server 192.168.122.200
# 配置允许上游时间服务器主动修改本机的时间
restrict 192.168.122.200 nomodify notrap noquery
includefile /etc/ntp/crypto/pw
keys /etc/ntp/keys
disable monitor

Also disable the chronyd service and enable the ntpd service. The client will automatically sync with the server 192.168.122.200.