Bird
Raised Fist0
AWScloud~5 mins

Connecting to EC2 instances in AWS - Cheat Sheet & Quick Revision

Choose your learning style10 modes available
LearnWhyDeepVisualTryChallengeProjectRecallTime

Start learning this pattern below

Jump into concepts and practice - no test required

or
Recommended
Test this pattern10 questions across easy, medium, and hard to know if this pattern is strong
Recall & Review
beginner
What is the primary method to securely connect to an EC2 instance running Linux?
Using SSH (Secure Shell) with a private key file (.pem) that matches the public key set during instance creation.
Click to reveal answer
beginner
What file permission should the private key (.pem) have before using it to connect to an EC2 instance?
The private key file should have permissions set to 400 (read-only for the owner) to ensure security and allow SSH to use it.
Click to reveal answer
beginner
Which protocol and port must be allowed in the EC2 security group to connect via SSH?
Protocol: TCP, Port: 22 must be allowed in the security group inbound rules to enable SSH connections.
Click to reveal answer
beginner
How do you connect to a Windows EC2 instance remotely?
Use Remote Desktop Protocol (RDP) with the instance's public IP and the Administrator password retrieved from the EC2 console using the private key.
Click to reveal answer
beginner
Why is it important to use a key pair when launching an EC2 instance?
The key pair provides a secure way to authenticate your access to the instance without using passwords, enhancing security.
Click to reveal answer
Which command is used to connect to a Linux EC2 instance using SSH?
Ardp -i mykey.pem ec2-user@ec2-public-ip
Bssh -i mykey.pem ec2-user@ec2-public-ip
Cconnect -key mykey.pem ec2-user@ec2-public-ip
Dssh ec2-user@localhost
What port must be open in the security group to allow SSH access?
A3389
B80
C22
D443
How do you retrieve the Administrator password for a Windows EC2 instance?
ADecrypt it using your private key in the EC2 console.
BYou set it during instance launch.
CUse the default password 'admin'.
DIt is emailed to you automatically.
What is the recommended permission setting for your private key file before connecting?
A777
B644
C000
D400
Which protocol is used to connect to a Windows EC2 instance remotely?
ARDP
BFTP
CSSH
DHTTP
Explain the steps to connect to a Linux EC2 instance from your local computer.
Think about the command and network settings needed.
You got /5 concepts.
    Describe how to connect to a Windows EC2 instance and retrieve the password.
    Focus on password retrieval and protocol used.
    You got /4 concepts.

      Practice

      (1/5)
      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'