Configure IP Address

Configure /etc/apt/source.list

https://gist.github.com/cho2/1f8bdf983f4d4a12651b60e578349740

deb http://ftp.sg.debian.org/debian/ stretch main contrib non-free 
deb http://ftp.sg.debian.org/debian/ stretch-updates main contrib non-free 
deb http://security.debian.org/ stretch/updates main contrib non-free

Update & Upgrade

$ apt update && apt upgrade

Sudo Access

$ apt-get install sudo
$ usermod -a -G sudo <username>

Package Manager, Firmware, Firewall, SSH

sudo apt-get install synaptic apt-xapian-index gdebi gksu firmware-linux ufw ssh rsync vim htop curl

Firewall Configuration

Add the default deny rule and we are good to go with a basic firewall.

$ sudo ufw default deny

The following single command is enough to enable the firewall and add it to startup.

sudo ufw enable

You can check the status by running the following commands

sudo ufw status
sudo ufw status verbose