​https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-18-04​
​https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands​
​https://www.digitalocean.com/community/tutorials/initial-server-setup-with-centos-7​
​https://linuxize.com/post/how-to-set-or-change-timezone-on-ubuntu-18-04/​
​https://devanswers.co/ubuntu-change-timezone-synchronize-ntp/​
​https://linuxize.com/post/how-to-add-swap-space-on-ubuntu-18-04/​
​https://www.digitalocean.com/community/tutorials/how-to-install-and-use-postgresql-on-ubuntu-18-04​
​https://www.digitalocean.com/community/tutorials/how-to-install-nginx-on-ubuntu-18-04​
​https://gorails.com/setup/ubuntu/18.04​
