SSH Access Methods

Overview

SSH (Secure Shell) allows you to control a remote machine using the command line.

┌──────────────┐                    ┌──────────────┐
│  Your        │      SSH (22)      │  EC2         │
│  Computer    │───────────────────▶│  Instance    │
│              │    Public IP       │  (Linux)     │
└──────────────┘                    └──────────────┘

Prerequisites

1. Security Group: Port 22 (SSH) open
2. Key Pair: .pem or .ppk file
3. Public IP: Instance must have public IP
4. Instance State: Running

SSH Methods by Operating System

chmod 0400 EC2Tutorial.pem
ssh -i EC2Tutorial.pem ec2-user@<PUBLIC_IP>

ssh -i EC2Tutorial.pem ec2-user@<PUBLIC_IP>

ssh -i EC2Tutorial.pem ubuntu@<PUBLIC_IP>

Method 1: SSH on Mac/Linux

Step 1: Prepare Key File

# Navigate to key location
cd ~/Downloads  # or wherever your key is

# Verify key exists
ls -la EC2Tutorial.pem

# Fix permissions (required!)
chmod 0400 EC2Tutorial.pem

Step 2: Connect

ssh -i EC2Tutorial.pem ec2-user@<PUBLIC_IP>

Breakdown:

• ssh - SSH command
• -i EC2Tutorial.pem - Identity file (private key)
• ec2-user - Default username for Amazon Linux 2
• @<PUBLIC_IP> - Instance public IP address

Step 3: First Connection

The authenticity of host '54.123.45.67' can't be established.
Are you sure you want to continue connecting (yes/no)? yes

Type yes to trust the host.

Step 4: Verify Connection

# You should see:
[ec2-user@ip-172-31-33-135 ~]$

# Test commands
whoami          # Returns: ec2-user
ping google.com # Test internet connectivity

Step 5: Exit

exit
# or press Ctrl+D

Method 2: SSH on Windows 10+

Using PowerShell

# Open PowerShell
# Navigate to key location
cd C:\Users\YourName\Desktop

# Verify SSH is available
ssh

# Connect
ssh -i EC2Tutorial.pem ec2-user@<PUBLIC_IP>

Fixing Permission Issues (Windows)

If you get permission errors:

1. Right-click .pem file → Properties
2. Security tab → Advanced
3. Disable inheritance → Remove all inherited permissions
4. Add → Select your username
5. Grant Full control
6. Owner: Change to your username

File Properties → Security → Advanced
├── Owner: YourUsername
├── Disable inheritance
└── Permission entries:
    └── YourUsername: Full control

Method 3: PuTTY (Windows 7/8)

Step 1: Install PuTTY

Download from: https://www.putty.org/

Step 2: Convert Key (PuTTYgen)

If you have .pem file:

1. Open PuTTYgen
2. Click Load → Select .pem file (show all files)
3. Click Save private key
4. Save as EC2Tutorial.ppk

Step 3: Configure PuTTY

1. Open PuTTY
2. Session:
   • Host Name: ec2-user@<PUBLIC_IP>
   • Port: 22
   • Connection type: SSH
3. Connection → SSH → Auth → Credentials:
   • Private key file: Browse to .ppk file
4. Session:
   • Saved Sessions: EC2 Instance
   • Click Save
5. Click Open

Step 4: Accept Host Key

Click Accept when prompted about host key.

Method 4: EC2 Instance Connect (Browser)

Steps

1. Go to EC2 Console → Instances
2. Select your instance
3. Click Connect
4. Choose EC2 Instance Connect tab
5. Username: ec2-user (auto-filled)
6. Click Connect

EC2 Console
└── Instances
    └── Select Instance
        └── Connect
            └── EC2 Instance Connect
                └── Connect (opens browser terminal)

Requirements

• Instance must have public IP
• Security Group must allow SSH (22) from AWS IP ranges
• Works with Amazon Linux 2 (and Amazon Linux 2023)

Troubleshooting Instance Connect

If connection fails:

1. Check Security Group has SSH (22) open
2. Try adding both IPv4 and IPv6 rules:
   • SSH from 0.0.0.0/0 (IPv4)
   • SSH from ::/0 (IPv6)

Default Usernames by AMI

Common SSH Commands

# Check who you are
whoami

# Check hostname
hostname

# Test internet
ping google.com

# View system info
uname -a

# Check disk space
df -h

# Exit session
exit

Troubleshooting

Questions & Answers