Instance templates in GCP - Step-by-Step Execution

Process Flow - Instance templates

Create Instance Template

↓

Define VM Settings

↓

Save Template

↓

Use Template to Create VMs

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VMs Launch with Template Settings

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Manage or Update Template

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Apply Updated Template to New VMs

You create an instance template by defining VM settings, save it, then use it to launch multiple VMs with the same configuration.

Execution Sample

GCP

gcloud compute instance-templates create my-template \
  --machine-type=e2-medium \
  --image-family=debian-11 \
  --image-project=debian-cloud

This command creates an instance template named 'my-template' with a specific machine type and Debian image.

Process Table

Step	Action	Input/Command	Result/State
1	Start creating instance template	gcloud compute instance-templates create my-template	Template creation initiated
2	Set machine type	--machine-type=e2-medium	Machine type set to e2-medium
3	Set image family and project	--image-family=debian-11 --image-project=debian-cloud	Image set to Debian 11 from debian-cloud project
4	Save template	Command execution completes	Instance template 'my-template' created and saved
5	Use template to create VM	gcloud compute instances create vm-1 --source-instance-template=my-template	VM 'vm-1' created with template settings
6	Verify VM settings	Check VM machine type and image	VM 'vm-1' has e2-medium machine and Debian 11 image
7	Update template (optional)	Create new template or modify settings	New or updated template ready for future VMs
8	Exit	No further commands	Process complete

💡 All steps completed; instance template created and used to launch VM

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
Template Name	None	my-template	my-template	my-template	my-template	my-template
Machine Type	None	e2-medium	e2-medium	e2-medium	e2-medium	e2-medium
Image	None	None	debian-11 (debian-cloud)	debian-11 (debian-cloud)	debian-11 (debian-cloud)	debian-11 (debian-cloud)
VM Created	No	No	No	No	Yes (vm-1)	Yes (vm-1)

Key Moments - 3 Insights

Why do we create an instance template instead of configuring each VM manually?

Instance templates let you define VM settings once and reuse them, saving time and ensuring consistency, as shown in steps 1-5 of the execution table.

Can we change the settings of an existing instance template after creation?

No, instance templates are immutable. To change settings, create a new template as indicated in step 7.

What happens if we launch a VM without specifying an instance template?

You must manually specify all VM settings. Using a template automates this, as shown in step 5 where the VM inherits template settings.

Visual Quiz - 3 Questions

Look at the execution table, what machine type is set after step 2?

A e2-small

B n1-standard-1

C e2-medium

D custom

💡 Hint

Check the 'Machine Type' variable in variable_tracker after Step 2

At which step is the VM 'vm-1' created using the instance template?

A Step 5

B Step 3

C Step 7

D Step 2

💡 Hint

Look for 'VM Created' status change in variable_tracker and 'Use template to create VM' in execution_table

If you want to change the VM image for future VMs, what should you do according to the execution flow?

A Update the VM after creation

B Create a new instance template with the new image

C Modify the existing instance template directly

D Delete the VM and recreate it

💡 Hint

Refer to step 7 in execution_table and key_moments about template immutability

Concept Snapshot

Instance templates define VM settings once
They include machine type, image, and other configs
Templates are immutable after creation
Use templates to launch consistent VMs quickly
Update by creating new templates
Simplifies VM management at scale

Full Transcript

Instance templates in Google Cloud let you save VM configurations like machine type and image in one reusable template. You start by creating a template with commands specifying these settings. Once saved, you can launch multiple VMs using this template, ensuring they all have the same setup. Templates cannot be changed after creation; to update settings, you create a new template. This process saves time and keeps VM setups consistent across your cloud environment.

Practice

1. What is the main purpose of an instance template in Google Cloud Platform?

easy

A. To store data permanently for virtual machines

B. To manage user access to virtual machines

C. To monitor the performance of virtual machines

D. To save VM configuration settings for creating identical instances quickly

Solution

1. Step 1: Understand what instance templates store

   Instance templates save the configuration details like machine type, disk image, and network settings.

2. Step 2: Identify their main use

   They allow quick creation of many identical VM instances without repeating setup.

3. Final Answer:

   To save VM configuration settings for creating identical instances quickly -> Option D

4. Quick Check:

   Instance templates = VM settings saved [OK]

Hint: Instance templates store VM setup for easy reuse [OK]

Common Mistakes:

• Confusing instance templates with storage or monitoring
• Thinking instance templates manage user permissions
• Assuming instance templates hold data permanently

2. Which of the following is the correct gcloud command to create an instance template named web-template with machine type e2-medium?

easy

A. gcloud compute instance-templates new web-template --type=e2-medium

B. gcloud compute instance-templates create web-template --machine-type=e2-medium

C. gcloud compute instances create web-template --machine-type=e2-medium

D. gcloud create instance-template web-template --machine e2-medium

Solution

1. Step 1: Identify the correct gcloud command for instance templates

   The command to create instance templates starts with gcloud compute instance-templates create.

2. Step 2: Check the machine type flag

   The correct flag is --machine-type= followed by the machine type.

3. Final Answer:

   gcloud compute instance-templates create web-template --machine-type=e2-medium -> Option B

4. Quick Check:

   Correct command syntax = gcloud compute instance-templates create web-template --machine-type=e2-medium [OK]

Hint: Use 'instance-templates create' with '--machine-type' flag [OK]

Common Mistakes:

• Using 'instances create' instead of 'instance-templates create'
• Wrong flag names like '--machine' or '--type'
• Incorrect command order or missing 'compute'

3. Given this snippet:

gcloud compute instance-templates create my-template \
  --machine-type=n1-standard-1 \
  --image-family=debian-11 \
  --image-project=debian-cloud

What will be the machine type of instances created from my-template?

medium

A. debian-11

B. e2-medium

C. n1-standard-1

D. debian-cloud

Solution

1. Step 1: Identify the machine type flag in the command

   The flag --machine-type=n1-standard-1 sets the machine type.

2. Step 2: Understand other flags

   --image-family and --image-project specify the OS image, not machine type.

3. Final Answer:

   n1-standard-1 -> Option C

4. Quick Check:

   Machine type flag sets instance type [OK]

Hint: Look for '--machine-type' flag for VM size [OK]

Common Mistakes:

• Confusing image family with machine type
• Choosing project name as machine type
• Ignoring the '--machine-type' flag

4. You tried to create an instance template with this command:

gcloud compute instance-templates create test-template --machine-type e2-small

But it failed. What is the likely error?

medium

A. Missing image or boot disk specification

B. Instance template name 'test-template' is invalid

C. Machine type 'e2-small' does not exist

D. Command should be 'gcloud create instance-template'

Solution

1. Step 1: Check required arguments for instance-templates create

   Instance templates require a machine type AND a boot disk specification (e.g., --image-family and --image-project).

2. Step 2: Validate other parts

   The instance template name and machine type are valid, and the command starts correctly with gcloud compute instance-templates create. Flag syntax with space is accepted.

3. Final Answer:

   Missing image or boot disk specification -> Option A

4. Quick Check:

   Instance templates need image spec [OK]

Hint: Include --image-family & --image-project flags [OK]

Common Mistakes:

• Forgetting to specify image or boot disk flags
• Wrong command order or missing 'compute'
• Assuming machine type is invalid without checking

5. You want to create a managed instance group that automatically updates all VMs when the instance template changes. Which approach should you use?

hard

A. Create a managed instance group with the instance template and enable rolling updates

B. Manually delete and recreate each VM after changing the template

C. Use an unmanaged instance group with the new template

D. Create a new instance template but keep the old managed group unchanged

Solution

1. Step 1: Understand managed instance groups and updates

   Managed instance groups can use instance templates and support rolling updates to replace VMs smoothly.

2. Step 2: Identify the best method for automatic updates

   Enabling rolling updates on the managed group with the new template applies changes automatically.

3. Final Answer:

   Create a managed instance group with the instance template and enable rolling updates -> Option A

4. Quick Check:

   Managed groups + rolling updates = automatic VM updates [OK]

Hint: Use managed groups with rolling updates for auto changes [OK]

Common Mistakes:

• Thinking unmanaged groups support automatic updates
• Manually recreating VMs instead of using rolling updates
• Ignoring instance template updates in managed groups