Launch templates in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

Understanding Launch Template Versioning

You have created an AWS EC2 launch template with multiple versions. You want to ensure that your Auto Scaling group always uses the latest version of the launch template when launching instances.

Which configuration setting in the Auto Scaling group will achieve this behavior?

A Specify the launch template name and set the version to '$Default' in the Auto Scaling group configuration.

B Specify the launch template ID and set the version to '1' in the Auto Scaling group configuration.

C Specify the launch template ID and set the version to '$Latest' in the Auto Scaling group configuration.

D Specify the launch template name and set the version to '0' in the Auto Scaling group configuration.

💡 Hint

Think about how AWS identifies the most recent version of a launch template.

Setting the version to '$Latest' tells the Auto Scaling group to always use the newest version of the launch template. Using a fixed version number like '1' will always use that specific version, ignoring updates.

❓ security

intermediate

Launch Template and IAM Role Association

You want to launch EC2 instances using a launch template that automatically assigns an IAM role to the instances for accessing S3 buckets securely.

Where should you specify the IAM role in the launch template configuration?

A Attach the IAM role directly to the EC2 instances after launch manually.

B In the launch template's 'IamInstanceProfile' section, specify the IAM role name or ARN.

C Specify the IAM role in the user data script of the launch template.

D Assign the IAM role to the VPC where the instances will launch.

💡 Hint

Consider how AWS associates IAM roles with EC2 instances at launch time.

The IAM role must be specified in the 'IamInstanceProfile' section of the launch template. This ensures instances launched from the template automatically receive the role.

❓ service_behavior

advanced

Effect of Changing Launch Template Data on Running Instances

You update the user data script in an existing launch template version and set this new version as the default. What happens to the EC2 instances that were launched using the previous launch template versions?

A The user data script update causes a reboot of all running instances to apply changes.

B All running instances automatically update their user data script to the new version.

C Existing instances are terminated and replaced with new instances using the updated launch template version.

D Existing instances continue running with their original user data; only new instances use the updated user data.

💡 Hint

Think about how launch templates affect instances after they are launched.

Launch templates define instance configuration at launch time only. Updating the template does not affect running instances; only new instances launched after the update use the new data.

❓ Configuration

advanced

Launch Template Network Interface Configuration

You want to create a launch template that launches EC2 instances with two network interfaces: one primary and one secondary. Which configuration in the launch template correctly defines this setup?

A Define two network interfaces in the 'NetworkInterfaces' section, marking one as 'DeviceIndex' 0 and the other as 'DeviceIndex' 1.

B Use the 'SubnetId' field twice in the launch template to create two interfaces automatically.

C Specify only one network interface in the launch template; add the second interface manually after instance launch.

D Create two separate launch templates, each with one network interface, and launch instances from both.

💡 Hint

Consider how AWS identifies multiple network interfaces on an instance.

The 'NetworkInterfaces' section allows specifying multiple interfaces with distinct 'DeviceIndex' values. 'DeviceIndex' 0 is the primary interface, and higher numbers are additional interfaces.

✅ Best Practice

expert

Managing Launch Template Versions for Production Stability

Your team uses launch templates for production EC2 instances. You want to deploy updates safely without affecting running instances and be able to roll back quickly if needed.

Which launch template versioning strategy best supports this goal?

A Create a new launch template version for each update, test it in staging, then update the Auto Scaling group to use the new version only after validation.

B Always use the '$Latest' version in the Auto Scaling group to ensure instances get the newest configuration immediately.

C Delete old launch template versions to keep only the current version for simplicity.

D Edit the default launch template version directly to apply changes instantly to all instances.

💡 Hint

Think about how to minimize risk and enable rollback when updating infrastructure.

Creating new versions and testing before updating the Auto Scaling group ensures stability. Using '$Latest' risks untested changes affecting production. Editing default versions or deleting old versions removes rollback options.

Practice

1. What is the main purpose of an AWS Launch Template?

easy

A. To automatically back up EC2 instance data

B. To monitor running EC2 instances in real-time

C. To store configuration settings for launching EC2 instances consistently

D. To manage user permissions for EC2 instances

Solution

1. Step 1: Understand Launch Template role

   Launch templates save settings like instance type, AMI, and security groups for EC2 instances.

2. Step 2: Identify main purpose

   This helps launch instances with consistent configurations quickly and easily.

3. Final Answer:

   To store configuration settings for launching EC2 instances consistently -> Option C

4. Quick Check:

   Launch Template = Configuration storage [OK]

Hint: Launch templates save instance settings for reuse [OK]

Common Mistakes:

• Confusing launch templates with monitoring tools
• Thinking launch templates handle backups
• Assuming launch templates manage permissions

2. Which of the following is the correct way to specify a launch template version in an AWS CLI command to run an EC2 instance?

easy

A. aws ec2 run-instances --launch-template LaunchTemplateId=lt-12345678,Version=2

B. aws ec2 run-instances --template-id lt-12345678 --version 2

C. aws ec2 run-instances --launch-template-id lt-12345678 --template-version 2

D. aws ec2 run-instances --launch-template lt-12345678 version=2

Solution

1. Step 1: Recall AWS CLI syntax for launch templates

   The correct syntax uses --launch-template with parameters LaunchTemplateId and Version separated by commas.

2. Step 2: Match syntax to options

   aws ec2 run-instances --launch-template LaunchTemplateId=lt-12345678,Version=2 matches the correct syntax exactly.

3. Final Answer:

   aws ec2 run-instances --launch-template LaunchTemplateId=lt-12345678,Version=2 -> Option A

4. Quick Check:

   Correct CLI syntax = aws ec2 run-instances --launch-template LaunchTemplateId=lt-12345678,Version=2 [OK]

Hint: Use --launch-template LaunchTemplateId=ID,Version=NUM [OK]

Common Mistakes:

• Using incorrect parameter names like --template-id
• Separating parameters with spaces instead of commas
• Omitting the 'Version=' keyword

3. Given this launch template version history:
Version 1: AMI ami-11111111, InstanceType t2.micro
Version 2: AMI ami-22222222, InstanceType t2.small
If you launch an instance specifying version 1, what will be the instance type?

medium

A. t2.small

B. t2.micro

C. t2.medium

D. The latest version's instance type

Solution

1. Step 1: Identify version specified in launch

   The question says version 1 is specified for launching the instance.

2. Step 2: Check instance type in version 1

   Version 1 has instance type t2.micro, so that will be used.

3. Final Answer:

   t2.micro -> Option B

4. Quick Check:

   Specified version settings apply = t2.micro [OK]

Hint: Specified version settings override latest [OK]

Common Mistakes:

• Assuming latest version is always used
• Confusing AMI with instance type
• Ignoring version number in launch command

4. You tried to launch an EC2 instance using a launch template but got an error: "Invalid launch template version specified." What is the most likely cause?

medium

A. The launch template ID is incorrect

B. The instance type is not supported in the region

C. The AMI in the launch template is deprecated

D. The specified version number does not exist in the launch template

Solution

1. Step 1: Analyze error message

   The error says "Invalid launch template version specified," indicating a problem with the version number.

2. Step 2: Identify cause

   This usually means the version number given does not exist or is mistyped.

3. Final Answer:

   The specified version number does not exist in the launch template -> Option D

4. Quick Check:

   Error about version = wrong version number [OK]

Hint: Check version number exists in template [OK]

Common Mistakes:

• Assuming AMI or instance type causes version error
• Not verifying launch template ID correctness
• Ignoring error details about version

5. You want to update a launch template to change the instance type but keep the original version intact for rollback. What is the best practice to achieve this?

hard

A. Create a new version of the existing launch template with the updated instance type

B. Modify the existing launch template version directly

C. Create a new launch template with the updated instance type

D. Delete the old launch template and create a new one with the updated instance type

Solution

1. Step 1: Understand launch template versioning

   Launch templates support multiple versions to track changes safely without overwriting.

2. Step 2: Choose update method preserving old version

   Creating a new version keeps the old version intact for rollback if needed.

3. Final Answer:

   Create a new version of the existing launch template with the updated instance type -> Option A

4. Quick Check:

   Use versioning to update safely = Create a new version of the existing launch template with the updated instance type [OK]

Hint: Use new version to update, keep old for rollback [OK]

Common Mistakes:

• Modifying existing version directly (not allowed)
• Deleting old template loses rollback option
• Creating new template duplicates effort unnecessarily