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⚙️ 06. SSH Overview and Connecting to EC2

SSH (Secure Shell) is a protocol used to securely connect to and manage remote servers such as Amazon EC2 instances. It provides encrypted communication between your local computer and the remote instance.

In AWS, SSH is primarily used to connect to Linux-based EC2 instances. For Windows instances, you typically use RDP (Remote Desktop Protocol) instead.

🔑 How SSH Works​

  • SSH uses a key pair (Public + Private key) for authentication instead of passwords.
  • When you launch an EC2 instance, you can:
    • Create a new key pair, or
    • Use an existing one.
  • The private key (.pem file) is downloaded once — it must be kept safe.
  • AWS stores the public key inside the EC2 instance to allow access.

When you connect, AWS verifies that your private key matches the public key on the instance.

🧰 Common SSH Commands (and SCP File Transfer)​

🔹 Connect to EC2 Using SSH​

# Basic SSH connection to EC2
ssh -i "my-key.pem" ec2-user@<Public-IP-Address>

# Example
ssh -i "aws-key.pem" ec2-user@13.233.25.10

⚙️ SFTP (SSH File Transfer Protocol)​

SFTP (SSH File Transfer Protocol) is a secure method for transferring files between your local computer and a remote EC2 instance over an encrypted SSH connection. It provides more control than scp — allowing you to browse directories, upload, download, rename, and delete files interactively.

Unlike traditional FTP (which uses port 21), SFTP runs over port 22 (the same as SSH), ensuring both data encryption and authentication.

🔑 How SFTP Works​

  • Uses the same SSH protocol for secure communication.
  • Authentication is done using your EC2 key pair (.pem file).
  • You can connect via the command line or GUI tools (like FileZilla, WinSCP, or Cyberduck).
  • Ideal for large file transfers, resumable uploads, and interactive directory navigation.

🧰 Common SFTP Commands​

# Connect to EC2 using your private key
sftp -i "my-key.pem" ec2-user@<Public-IP-Address>

# Upload a file to EC2
put localfile.txt /home/ec2-user/

# Download a file from EC2
get /home/ec2-user/output.log

# Change local and remote directories
lcd /Users/himanshu/Documents
cd /var/www/html