Note : On drupal the best practice is use drupal behaviors but not JS or Jquery codes such as:
<button onclick='myFunction()'>Click</button>

keyvalue.expirable service allow to save Key / Value variable in the database.

Example:

// Save without date limit.
\Drupal::service('keyvalue.expirable')->get('my_module')->set('my_var', 123);

Webmin and Virtualmin Change IP access control from shell terminal.

Edit file: /etc/webmin/miniserv.conf
vim /etc/webmin/miniserv.conf

Change:
allow=OLD_IP to New IP
Example:
allow=123.214.123.123 85.25.65.45 45.65.85.36

Drush allow to download and install drupal core, drupal modules and drupal themes.
Note : It is recommended to use composer to manage drupal 8, modules and themes.

SCP - Secure copy

Download a file via SCP
File :        /tmp/mysql.dump.sql
Server/Login :    THE_USERNAME:PASSWORD@domain.com
Download to :     . (Current directory)
scp user:pass@domain.com:/tmp/mysql.dump.sql .