Linux implements NTP server time synchronization, which can be realized through ntp service or chrony service
The difference between the two is mainly
Chrony runs on UDP port 323, NTP runs on UDP port 123
Chrony can be synchronized faster than NTP, and can maximize synchronization to reduce time and frequency errors
Chrony responds better to rapid changes in clock frequency, which is useful for VMs with unstable clocks
Chronyc does not need to periodically poll the server, and can still quickly synchronize the clock for systems with intermittent network connections
Chrony mainly includes two core components
chronyd: A daemon that can be started at boot time to adjust the system clock running in the kernel to synchronize with the NTP server
chronyc: a command-line interface program that monitors the performance of chronyd and changes various operating parameters while it is running
Configure Chrony
install chrony
yum -y install chrony
systemctl start chronyd.service
systemctl enable chronyd.service
Configure the main configuration file of chronyc -- the main configuration file of chrony is /etc/chrony.conf
vim /etc/chrony.conf
server NTP server address iburst
allow 172.25/16 allows 172.16 to access the NTP server
NTP synchronization through iburst, the first synchronization time will be faster
supplementary configuration
firewall-cmd --add-service=ntp --permanent release ntp service
firewall-cmd --reload
firewall-cmd --list-all
timedatectl set-ntp true change ntp synchronization to true
systemctl restart chronyd.service Restart the chrony service
authenticating
chronyc activity -v Check if ntp_server is online
chronyc -a makestep Force synchronization of the system clock
chronyc tracking -v View ntp details
chronyc sources -v to verify
* means synchronized
? Indicates unreachable
timedatectl View system time
Commonly used NTP servers
time1.cloud.tencent.com
time.aliyun.com
time.apple.com
asia.pool.ntp.org