Deep Dive into EC2 – Ports, IPs, SSH Users, and More

Okay, I thought I was kind of done with EC2 after installing both NGINX and Apache... but turns out, there’s still a lot left to play with. Today, I went a little deeper into EC2 — not just launching instances, but actually exploring how networking and users work.

It was all stuff that seemed “extra” before, but now I’m realizing it’s essential. Here’s what I messed with today:

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1. Playing with Security Groups and Ports

I started by modifying the Security Group of my EC2 instance. My goal: see what happens when I open or close ports manually.

Things I tried:

• Removed port 80 → Website became unreachable

• Re-added it → Site came back online

• Opened port 3000 to prepare for a future app

• Opened port 22 to SSH from another device

I also restricted port 22 to my IP only — a security best practice I had no idea about until now.

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2. Creating a New SSH User on EC2

This part was fun. I created a new Linux user:

sudo adduser devuser

Now I could SSH into the instance as devuser, not just ec2-user. Felt more "real world".

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3. Understanding Sudo Permissions

By default, the new user couldn’t use sudo, so I added it:

sudo usermod -aG wheel devuser

Then I switched to devuser and tested it:

sudo ls

It worked!
I'm slowly understanding how Linux users and permissions work inside EC2.

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4. Static IPs: Why I Need an Elastic IP

Here’s something that tripped me up.

When I stopped and started my EC2 instance, its public IP changed 😬
That meant I had to update my browser or SSH every time.

Solution? Elastic IPs.
So I:

• Went to EC2 > Elastic IPs

• Allocated a new one

• Associated it with my running EC2 instance

Now I have a fixed IP I can use — much better for a blog or app.

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5. Understanding the EC2 Lifecycle

I played with the EC2 stop/start/reboot/terminate buttons.

Observations:

• Stop → Start: Data persisted, but IP changed (until I used Elastic IP)

• Reboot: Quick restart, data safe

• Terminate: Wipes everything — like formatting your PC. Scary, but good to know.

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6. Installing Extra Tools on EC2

Since it’s just Linux, I figured — why not install something?

I tried:

sudo dnf install git -y
sudo dnf install python3 -y

Both worked great.
This EC2 instance is starting to feel like my personal dev playground now.

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What I Learned Today

• Security groups are like EC2 firewalls — powerful but simple once you get them

• I can manage users and SSH just like a regular Linux box

• Elastic IPs are a must if I want a stable setup

• I now understand the difference between reboot, stop, and terminate

• EC2 is more than "just a server" — it's a mini-data center at my fingertips