Linux System Variables
Date, time, language

Locale, Date & Time
Locale 
 In Linux, a locale is a set of environment variables that defines the language, country, and character encoding settings for a user's environment. Locales affect various aspects of a program's behavior, such as the way dates and times are displayed, the format of numbers, the sort order of strings, and the language used for messages. 
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 View locale configuration 
 localectl 
 and 
 locale 
 View specific locale variable option 
 locale LC_NUMERIC 
 View available locales 
 localectl list-locales 
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 Setting locale 
 localectl set-locale LANG=fr_FR.utf8 
 (reboot may be required) 
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 Time 
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 Check system time 
 date 
 or for more detail 
 timedatectl 
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 NTP 
 View current NTP configuration: 
 timedatectl show-timesync --all 
 Enable NTP 
 timedatectl set-ntp on 
 Disable NTP 
 timedatectl set-ntp off 
 NTP Server selection 
 Most mainstream Linux distributions come with NTP servers preconfigured, these can be altered however, this is done via the /etc/systemd/timesync.conf file. Simply add a new line to the file formatted as follows: 
 NTP=NTPSERVERHOSTNAME 
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 Timezone 
 Check available timezones 
 timedatectl list-timezones 
 Set server timezone 
 timedatectl set-timezone timezonename 
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Hostname
Show current server hostname: 
 hostname 
 Show current server hostname, and other useful info: 
 hostnamectl status 
 example output: 
 root@test:~# hostnamectl status

Static hostname: test

      Icon name: computer-vm

        Chassis: vm

     Machine ID: 8c1d97558b594586af68685af4a049c9

        Boot ID: c2478c600d2b43f0bf58682f1df01013

 Virtualization: kvm
Operating System: Ubuntu 22.04.3 LTS

         Kernel: Linux 5.15.0-106-generic

   Architecture: x86-64

Hardware Vendor: QEMU

 Hardware Model: Standard PC _i440FX + PIIX, 1996_ 
 Change server hostname: