Correctly set time in computer systems allows for the correct operation of running programs and easy search of logs between different computer systems. If the time in each system is different, any log analyzes (e.g. for post-intrusion analysis) in your infrastructure will be difficult. The following NTP server time synchronization configuration will work on any modern Linux distribution that uses systemd.

We will use the command to verify the current time settings timedatectl.

user@linux :~ $ timedatectl
                Local time : Tue 2020 - 07 - 14 18 : 35 : 04 UTC
            Universal time : Tue 2020 - 07 - 14 18 : 35 : 04 UTC      
                 RTC time : Tue 2020 - 07 - 14 18 : 35 : 04 Time zone : Etc / UTC ( UTC , + 0000 ) System clock synchronized : yes   
                  

              NTP service : active
          RTC in local TZ : no

You may notice that the current time zone is set to Etc/UTC. The following command is used to display the available time zone names.

user@linux :~ $ timedatectl list - timezones
 Africa / Abidjan Africa / Accra Africa / Algiers Africa / Bissau Africa / Cairo Africa / Casablanca Africa / Ceuta (…)

In the case of Poland, the appropriate time zone is Europe/Warsaw. To change the settings, elevation of privileges is required, e.g. using sudo.

user@linux :~ $ sudo timedatectl set - timezone Europe / Warsaw 
user@linux :~ $ timedatectl
 Local time : Tue 2020 - 07 - 14 20 : 36 : 18 CEST
 Universal time : Tue 2020 - 07 - 14 18 : 36 : 18 UTC      
RTC time : Tue 2020 - 07 - 14 18 : 36 : 18 Time zone : Europe / Warsaw ( CEST , + 0200 ) System clock synchronized : yes   
   

NTP service : active
RTC in local TZ : no

After changing the time zone, verify the configuration again with timedatectl. In my case, time synchronization with NTP servers is enabled by default. To enable or disable synchronization with an NTP server, use the command:

user@linux :~ $ sudo timedatectl set - ntp on

user@linux :~ $ sudo timedatectl set - ntp off

To change the default NTP server, edit the configuration file and enter the time server addresses.

user@linux :~ $ sudo nano / etc / systemd / timesyncd . conf

[ Time ] 
NTP = tempus1 . gum . gov . pl tempus2 . gum . gov . pl
 FallbackNTP = ntp . ubuntu . com

After configuring the new NTP servers, restart the time synchronization service and verify the synchronization status again.

user@linux :~ $ sudo systemctl restart systemd - timesyncd . service
user@linux :~ $timedatectl

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