devops

Creating an EC2 Instance

Step-by-step: launch an EC2 instance, connect via SSH, and set up a basic web server

Prerequisites

AWS account (free tier works fine)
AWS CLI configured (aws configure)
A terminal with SSH

Method 1: AWS Console (GUI)

Step 1 — Open the EC2 Dashboard

Go to AWS Console → Services → EC2 → Launch Instance

Step 2 — Name your instance

Give it a name, e.g. my-first-server

Step 3 — Choose an AMI

Select Amazon Linux 2023 (free tier eligible, modern, fast)

Step 4 — Choose instance type

Select t2.micro or t3.micro — free tier eligible

Step 5 — Key Pair

Click Create new key pair
Name: my-keypair
Type: RSA, format: .pem
Download it — you cannot download it again!
Move it somewhere safe: mv ~/Downloads/my-keypair.pem ~/.ssh/
Lock the permissions: chmod 400 ~/.ssh/my-keypair.pem

Step 6 — Security Group

Create a new security group. Add these inbound rules:

Type	Port	Source
SSH	22	My IP (select from dropdown)
HTTP	80	Anywhere (0.0.0.0/0)

Step 7 — Storage

Keep the default 8 GiB gp3 root volume (free tier: up to 30 GiB)

Step 8 — Launch!

Click Launch Instance. After ~30 seconds, state changes to Running.

Method 2: AWS CLI

# Find the latest Amazon Linux 2023 AMI ID in your region
aws ec2 describe-images \
  --owners amazon \
  --filters "Name=name,Values=al2023-ami-*-x86_64" \
  --query "sort_by(Images, &CreationDate)[-1].ImageId" \
  --output text

# Launch instance (replace ami-xxxxxxxx with the ID above)
aws ec2 run-instances \
  --image-id ami-xxxxxxxx \
  --instance-type t3.micro \
  --key-name my-keypair \
  --security-group-ids sg-xxxxxxxx \
  --subnet-id subnet-xxxxxxxx \
  --count 1 \
  --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=my-first-server}]'

# Get the public IP of your running instance
aws ec2 describe-instances \
  --filters "Name=tag:Name,Values=my-first-server" \
  --query "Reservations[0].Instances[0].PublicIpAddress" \
  --output text

Connecting via SSH

# Linux / macOS
ssh -i ~/.ssh/my-keypair.pem ec2-user@<PUBLIC_IP>

# Windows (PowerShell — native OpenSSH)
ssh -i C:\Users\you\.ssh\my-keypair.pem ec2-user@<PUBLIC_IP>

Default usernames by AMI:

Amazon Linux → ec2-user

Ubuntu → ubuntu

Debian → admin

CentOS → centos

Quick Setup: Install a Web Server

Once SSH’d in:

# Update packages
sudo dnf update -y

# Install nginx
sudo dnf install -y nginx

# Start and enable on boot
sudo systemctl start nginx
sudo systemctl enable nginx

# Check status
sudo systemctl status nginx

Now visit http://<PUBLIC_IP> in your browser — you should see the nginx welcome page.

Stopping vs Terminating

# Stop (instance off, data kept, small EBS cost continues)
aws ec2 stop-instances --instance-ids i-xxxxxxxxxxxxxxxxx

# Start again
aws ec2 start-instances --instance-ids i-xxxxxxxxxxxxxxxxx

# Terminate (instance + root volume deleted — gone forever)
aws ec2 terminate-instances --instance-ids i-xxxxxxxxxxxxxxxxx

Free tier tip: Stop instances when not in use. Terminate them when done to avoid any charges.

Common Issues

Problem	Cause	Fix
`Permission denied (publickey)`	Wrong key or wrong user	Check `-i` path and username
`Connection timed out`	Port 22 not open	Check security group inbound rules
`UNPROTECTED PRIVATE KEY`	`.pem` permissions too open	`chmod 400 ~/.ssh/my-keypair.pem`
Can’t reach port 80	HTTP not in security group	Add inbound rule for port 80