Launch templates in AWS - Step-by-Step Execution

Process Flow - Launch templates

Create Launch Template

↓

Define Configurations

↓

Save Template Version

↓

Launch EC2 Instance Using Template

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Instance Runs with Template Settings

↓

Optionally Create New Template Version

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Repeat Launch with Updated Configurations

The flow shows creating a launch template, defining settings, saving it, launching instances from it, and optionally updating the template for future launches.

Execution Sample

AWS

aws ec2 create-launch-template --launch-template-name MyTemplate --version-description v1 --launch-template-data '{"ImageId":"ami-12345678","InstanceType":"t2.micro"}'
aws ec2 run-instances --launch-template LaunchTemplateName=MyTemplate,Version=1

This code creates a launch template with an AMI and instance type, then launches an EC2 instance using that template.

Process Table

Step	Action	Input/Condition	Result/Output
1	Create launch template	Name=MyTemplate, Version=v1, Data={ImageId=ami-12345678, InstanceType=t2.micro}	Launch template MyTemplate version 1 created
2	Launch instance	Use LaunchTemplateName=MyTemplate, Version=1	EC2 instance launched with AMI ami-12345678 and type t2.micro
3	Instance state	Instance initializing	Instance state: pending
4	Instance state	Instance booting	Instance state: running
5	Optional: create new version	Update InstanceType to t3.micro	Launch template MyTemplate version 2 created
6	Launch instance	Use LaunchTemplateName=MyTemplate, Version=2	EC2 instance launched with AMI ami-12345678 and type t3.micro
7	End	No more launches	Execution stops

💡 No more instances to launch, process ends

Status Tracker

Variable	Start	After Step 1	After Step 5	Final
LaunchTemplateName	None	MyTemplate	MyTemplate	MyTemplate
Version	None	1	2	2
ImageId	None	ami-12345678	ami-12345678	ami-12345678
InstanceType	None	t2.micro	t3.micro	t3.micro
InstanceState	None	None	running	running

Key Moments - 3 Insights

Why do we need to specify a version when launching an instance?

Each launch template version can have different settings. Specifying the version ensures the instance uses the correct configuration, as shown in execution_table steps 2 and 6.

Can we update a launch template directly without creating a new version?

No, launch templates are immutable. To change settings, you create a new version (step 5), preserving previous versions for reuse.

What happens if we launch an instance without specifying a version?

AWS uses the default version of the launch template. This is not shown in the table but is important to know to avoid unexpected configurations.

Visual Quiz - 3 Questions

Look at the execution_table, what is the InstanceType used at step 6?

A t2.micro

B t3.micro

C ami-12345678

D pending

💡 Hint

Check the 'Result/Output' column at step 6 for the instance type.

At which step is a new launch template version created?

A Step 3

B Step 2

C Step 5

D Step 7

💡 Hint

Look for 'Launch template MyTemplate version 2 created' in the Result/Output column.

If we did not specify a version when launching an instance, what would happen?

A AWS uses the default launch template version

B AWS creates a new launch template version automatically

C The instance launch would fail

D The instance uses the latest version always

💡 Hint

Refer to key_moments explanation about default version usage.

Concept Snapshot

Launch templates store EC2 instance settings as reusable versions.
Create a template with configurations like AMI and instance type.
Launch instances by specifying template name and version.
Update settings by creating new versions, preserving old ones.
Using versions ensures consistent and repeatable instance launches.

Full Transcript

Launch templates in AWS let you save EC2 instance settings in a reusable way. First, you create a launch template with a name and version, defining details like the AMI and instance type. Then, you launch EC2 instances by referring to the template name and version. The instance starts with the saved settings. If you want to change settings, you create a new version of the launch template. This way, you keep old versions intact and can launch instances with different configurations as needed. Always specify the version when launching to control which settings are used. If you don't specify, AWS uses the default version. This process helps manage EC2 launches easily and consistently.

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