[NOTE] ClockSynchronize

Ubuntu

• Check your current time-zone: cat /etc/timezone
• Check if your clock is synchronized with the internet: timedatectl

root@openstack1:~/kubernetes# timedatectl
                      Local time: Tue 2019-12-17 10:30:02 UTC
                  Universal time: Tue 2019-12-17 10:30:02 UTC
                        RTC time: Tue 2019-12-17 10:30:02
                       Time zone: Etc/UTC (UTC, +0000)
       System clock synchronized: yes
systemd-timesyncd.service active: yes
                 RTC in local TZ: no

If you haven’t sychronized with internet, the value of System clock synchronize must be no

Use sudo systemctl restart systemd-timesyncd.service to activate timesyncd

root@openstack1:~/kubernetes# systemctl status systemd-timesyncd.service
● systemd-timesyncd.service - Network Time Synchronization
   Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendo
   Active: active (running) since Mon 2019-12-16 09:24:02 UTC; 1 day 1h ago
     Docs: man:systemd-timesyncd.service(8)
 Main PID: 27584 (systemd-timesyn)
   Status: "Synchronized to time server 91.189.94.4:123 (ntp.ubuntu.com)."
    Tasks: 2 (limit: 4915)
   CGroup: /system.slice/systemd-timesyncd.service
           └─27584 /lib/systemd/systemd-timesyncd

• The final key to synchronize the clock

sudo timedatectl set-ntp true

• Switch your time-zone

timedatectl list-timezones to check all the time-zones.

sudo timedatectl set-timezone Asia/Shanghai

CentOS

• Using command line

  # installation
  yum install chrony
  # enable chronyd
  systemctl start chronyd
  systemctl enable chronyd
  # set timezone to Shanghai
  timedatectl set-timezone Asia/Shanghai
  # launch it
  timedatectl set-ntp yes