I will give an example of setting time synchronization on Ubuntu Server 18.04.
In Ubuntu 18, the systemd-timesyncd service is enabled by default and time synchronization reports can be seen in the /var/log/syslog file, for example:
systemd-timesyncd[979]: Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com)
In the configuration file /etc/systemd/timesyncd.conf, you can see the standard values for some parameters that can be uncommented and changed:
[Time]
#NTP=
#FallbackNTP=ntp.ubuntu.com
#RootDistanceMaxSec=5
#PollIntervalMinSec=32
#PollIntervalMaxSec=2048
For example, in order to synchronize time approximately once a day:
[Time]
#NTP=
#FallbackNTP=ntp.ubuntu.com
#RootDistanceMaxSec=5
#PollIntervalMinSec=32
#PollIntervalMaxSec=2048
PollIntervalMinSec=86400
PollIntervalMaxSec=90000
Restart systemd-timesyncd to apply the changes:
systemctl restart systemd-timesyncd.service
systemctl status systemd-timesyncd.service
Let’s see the current time settings:
timedatectl
date
I have displayed:
Local time: Mon 2020-07-13 22:07:45 EEST
Universal time: Mon 2020-07-13 19:07:45 UTC
RTC time: Mon 2020-07-13 19:07:45
Time zone: Etc/UTC (EEST, +0300)
System clock synchronized: yes
systemd-timesyncd.service active: yes
RTC in local TZ: no
To disable time synchronization, you can do:
timedatectl set-ntp off
Check the status of the service (should not be started and disabled):
systemctl status systemd-timesyncd.service
systemctl is-enabled systemd-timesyncd.service
If necessary, you can turn it back on:
timedatectl set-ntp on
Example time zone changes:
timedatectl list-timezones
timedatectl list-timezones | grep -i europe
timedatectl set-timezone Europe/Kiev
Example of manual time setting:
timedatectl set-time 2020-07-14 11:08:00
See also my article:
Configuring NTP Client and NTP Server in Linux