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.
Download a file via SCP
File :Â Â Â Â Â Â /tmp/mysql.dump.sql
Server/Login :Â Â Â THE_USERNAME:PASSWORD@domain.com
Download to : Â Â Â . (Current directory) scp user:pass@domain.com:/tmp/mysql.dump.sql .
To create a bootable USB memory on linux you have several solutions. The famous dd is the most powerful solution, but use carefully. Because a very small error may destroy all your data.