4  Ubuntu Server

ndexr servers run Ubuntu. Whether you’re working on an EC2 instance or a local machine, the fundamentals are the same.

4.1 Installing Ubuntu locally (optional)

If you want a local development server — an old laptop or desktop works — install Ubuntu Server:

  1. Download the Ubuntu Server LTS ISO
  2. Create a bootable USB drive
  3. Boot from USB, accept defaults, connect to WiFi during installation (setting up WiFi post-install is significantly harder)
  4. If anything goes wrong, reformat and start over — that’s the point of using an old machine

You don’t need a local server to use ndexr. EC2 instances launched through the console come fully configured. But having one helps you understand what’s happening on the server side.

4.2 First steps on a server

After logging in (either locally or via SSH), update everything:

sudo apt update
sudo apt upgrade -y

Install basic networking tools:

sudo apt install net-tools -y

4.3 Finding your IP address

Use ifconfig to see your network interfaces:

ifconfig

Look for the inet value under your network interface (eth0 for wired, wlan0 or wlp* for wireless):

wlp0s20f3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
       inet 192.168.0.152  netmask 255.255.255.0

IPs starting with 192.168.* are local — they’re only reachable from your home network. Your EC2 instance has a public IP assigned by AWS.

4.4 Connecting remotely

Install the SSH client if needed:

sudo apt install openssh-client -y

Connect to any server:

ssh username@server_ip_address

For EC2 instances launched through ndexr:

ssh -i ~/my-key.pem ubuntu@your-server-ip

The first time you connect, you’ll be asked to verify the host fingerprint. Type yes.

4.5 The local vs. remote mental model

Your laptop at 192.168.0.152 and your EC2 instance at 3.130.103.243 are fundamentally the same thing — a computer running Ubuntu. The difference is that the EC2 instance has a public IP address reachable from the internet, and your laptop is behind your router’s NAT.

Everything you learn on a local server applies to EC2, and vice versa.