Connecting to EC2 instances in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the key pair file when connecting to an EC2 instance using SSH.

AWS

ssh -i [1] [e-mail]

Drag options to blanks, or click blank then click option'

Amy-key.key

Bmy-key.txt

Cmy-key.pub

Dmy-key.pem

Attempts:

3 left

💡 Hint

Common Mistakes

Using the public key file (.pub) instead of the private key (.pem)

Using a text file or wrong extension for the key

The -i option specifies the private key file with a .pem extension used for SSH authentication.

2fill in blank

medium

Complete the command to connect to an EC2 instance with the correct username for Amazon Linux.

AWS

ssh -i my-key.pem [1]@ec2-198-51-100-1.compute-1.amazonaws.com

Drag options to blanks, or click blank then click option'

Aec2-user

Bubuntu

Cadmin

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using root which is disabled by default

Using ubuntu for Amazon Linux instances

Amazon Linux EC2 instances use ec2-user as the default SSH username.

3fill in blank

hard

Fix the error in the SSH command to connect to an EC2 instance by selecting the correct option for the port number.

AWS

ssh -i my-key.pem -p [1] [e-mail]

Drag options to blanks, or click blank then click option'

A22

B8080

C443

D3306

Attempts:

3 left

💡 Hint

Common Mistakes

Using HTTP or database ports instead of SSH port

Omitting the port option when a non-standard port is required

SSH uses port 22 by default. Using the correct port ensures the connection succeeds.

4fill in blank

hard

Fill both blanks to create a security group rule allowing SSH access from anywhere.

AWS

aws ec2 authorize-security-group-ingress --group-id sg-123abc --protocol [1] --port [2] --cidr 0.0.0.0/0

Drag options to blanks, or click blank then click option'

Atcp

Budp

C22

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using UDP instead of TCP

Opening port 80 which is for HTTP, not SSH

SSH uses the TCP protocol on port 22. This command opens port 22 for SSH access.

5fill in blank

hard

Fill all three blanks to create an SSH command that connects to an EC2 instance with a specific key, user, and IP address.

AWS

ssh -i [1] [2]@[3]

Drag options to blanks, or click blank then click option'

Amy-ec2-key.pem

Bec2-user

C54.201.123.45

Dubuntu

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong username like ubuntu for Amazon Linux

Using a domain name instead of the IP address

The command uses the private key file my-ec2-key.pem, the default user ec2-user, and the instance's public IP address 54.201.123.45.

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'