Connecting to EC2 instances in AWS - Mini Project: Build & Apply

Connecting to EC2 instances

📖 Scenario: You are setting up a cloud server using Amazon EC2. To manage your server, you need to connect to it securely using SSH. This project will guide you step-by-step to prepare and connect to your EC2 instance.

🎯 Goal: Learn how to prepare your SSH key, configure your EC2 instance's security group, and connect to the instance using the terminal.

📋 What You'll Learn

Create a variable with the EC2 instance's public DNS name

Create a variable with the path to your SSH private key file

Write the SSH command string to connect to the EC2 instance

Add the option to use the SSH key file in the SSH command

💡 Why This Matters

🌍 Real World

Connecting to EC2 instances is a fundamental skill for managing cloud servers securely and remotely.

💼 Career

Cloud engineers and system administrators regularly connect to EC2 instances to deploy, monitor, and maintain applications.

1

Set the EC2 instance public DNS

Create a variable called ec2_public_dns and set it to the exact string "ec2-3-123-45-67.compute-1.amazonaws.com" which represents your EC2 instance's public DNS name.

AWS

# Create a variable called ec2_public_dns with the EC2 instance public DNS
# Your code here

Hint

The EC2 public DNS is a string that looks like a web address. Assign it exactly as shown.

2

Set the SSH private key file path

Create a variable called ssh_key_path and set it to the exact string "~/.ssh/my-ec2-key.pem" which is the path to your SSH private key file.

AWS

ec2_public_dns = "ec2-3-123-45-67.compute-1.amazonaws.com"
# Create a variable called ssh_key_path with the SSH private key file path
# Your code here

Hint

The SSH key file path is a string that points to your private key file on your computer.

3

Write the SSH command string

Create a variable called ssh_command and set it to the exact string "ssh ec2-user@" + ec2_public_dns which forms the basic SSH command to connect to your EC2 instance.

AWS

ec2_public_dns = "ec2-3-123-45-67.compute-1.amazonaws.com"
ssh_key_path = "~/.ssh/my-ec2-key.pem"
# Create a variable called ssh_command with the SSH command string
# Your code here

Hint

The SSH command starts with 'ssh ec2-user@' followed by the EC2 public DNS.

4

Add the SSH key option to the command

Update the ssh_command variable to include the SSH key file option by setting it to the exact string "ssh -i " + ssh_key_path + " ec2-user@" + ec2_public_dns so you can connect securely using your private key.

AWS

ec2_public_dns = "ec2-3-123-45-67.compute-1.amazonaws.com"
ssh_key_path = "~/.ssh/my-ec2-key.pem"
ssh_command = "ssh ec2-user@" + ec2_public_dns
# Update ssh_command to include the -i option with ssh_key_path
# Your code here

Hint

The '-i' option tells SSH which private key file to use for authentication.

Practice

1. What is the primary method to securely connect to an AWS EC2 Linux instance?

easy

A. Using FTP with username and password

B. Using HTTP protocol

C. Using SSH with a private key file

D. Using RDP without any credentials

Solution

1. Step 1: Understand connection protocols for EC2 Linux

   Linux EC2 instances use SSH (Secure Shell) for secure remote access.

2. Step 2: Identify the authentication method

   SSH requires a private key file (.pem) to authenticate securely without passwords.

3. Final Answer:

   Using SSH with a private key file -> Option C

4. Quick Check:

   SSH + private key = secure EC2 Linux access [OK]

Hint: SSH with private key is standard for Linux EC2 [OK]

Common Mistakes:

• Trying to use HTTP or FTP for EC2 Linux connection
• Using RDP which is for Windows instances
• Connecting without a private key

2. Which command correctly connects to an EC2 instance with IP 203.0.113.25 using the private key file mykey.pem and default username ec2-user?

easy

A. ssh -key mykey.pem ec2-user@203.0.113.25

B. ssh -i mykey.pem ec2-user@203.0.113.25

C. ssh ec2-user@203.0.113.25 -i mykey.pem

D. ssh -pem mykey.pem ec2-user@203.0.113.25

Solution

1. Step 1: Recall SSH command syntax for private key

   The correct syntax is ssh -i <keyfile> <user>@<ip>.

2. Step 2: Match the command with the syntax

   ssh -i mykey.pem ec2-user@203.0.113.25 matches the correct order and flags exactly.

3. Final Answer:

   ssh -i mykey.pem ec2-user@203.0.113.25 -> Option B

4. Quick Check:

   ssh -i keyfile user@ip = correct syntax [OK]

Hint: Use -i before key file in ssh command [OK]

Common Mistakes:

• Placing -i after user@ip
• Using -key or -pem flags which don't exist
• Omitting the -i flag

3. Given the command ssh -i mykey.pem ubuntu@198.51.100.10, what will happen if the private key file mykey.pem has permissions set to 777?

medium

A. Connection will fail due to insecure key file permissions

B. Connection will succeed without warnings

C. SSH will prompt for a password instead

D. The instance will reject the username 'ubuntu' automatically

Solution

1. Step 1: Understand SSH key file permission requirements

   SSH requires private key files to have strict permissions (usually 400 or 600) to prevent unauthorized access.

2. Step 2: Effect of 777 permissions on SSH connection

   Permissions 777 are too open, so SSH refuses to use the key and fails the connection.

3. Final Answer:

   Connection will fail due to insecure key file permissions -> Option A

4. Quick Check:

   Too open key permissions = connection failure [OK]

Hint: Private key must have strict permissions (chmod 400) [OK]

Common Mistakes:

• Assuming connection works with any key permissions
• Thinking SSH will ask for password if key is insecure
• Believing username causes rejection here

4. You try to connect to your EC2 instance but get a timeout error. Which of the following is the MOST likely cause?

medium

A. Your private key file is missing

B. The instance is running Windows OS

C. You used the wrong username for the instance

D. Your security group does not allow inbound SSH (port 22) traffic

Solution

1. Step 1: Analyze timeout error causes

   Timeout usually means network traffic is blocked or unreachable, not authentication issues.

2. Step 2: Check security group rules

   If inbound SSH (port 22) is not allowed, connection attempts will time out.

3. Final Answer:

   Your security group does not allow inbound SSH (port 22) traffic -> Option D

4. Quick Check:

   Timeout = blocked port 22 in security group [OK]

Hint: Check security group allows port 22 inbound [OK]

Common Mistakes:

• Confusing timeout with wrong username errors
• Assuming missing key causes timeout instead of auth failure
• Thinking OS type causes timeout

5. You have an EC2 instance running Amazon Linux and another running Ubuntu. Which usernames should you use to connect via SSH respectively?

hard

A. ec2-user for Amazon Linux, ubuntu for Ubuntu

B. root for Amazon Linux, admin for Ubuntu

C. admin for Amazon Linux, ec2-user for Ubuntu

D. ubuntu for Amazon Linux, ec2-user for Ubuntu

Solution

1. Step 1: Identify default SSH usernames per OS

   Amazon Linux uses ec2-user and Ubuntu uses ubuntu as default SSH usernames.

2. Step 2: Match usernames to instances

   Use ec2-user for Amazon Linux and ubuntu for Ubuntu instances.

3. Final Answer:

   ec2-user for Amazon Linux, ubuntu for Ubuntu -> Option A

4. Quick Check:

   Amazon Linux = ec2-user, Ubuntu = ubuntu [OK]

Hint: Match username to OS: ec2-user for Amazon Linux [OK]

Common Mistakes:

• Using root or admin instead of default usernames
• Mixing usernames between OS types
• Assuming username is always 'admin'