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Instance Template creation and Creating Instance using Instance Template

  • Date 6th October, 2026 |
  • By Prwatech |
  • 0 Comments

Instance Templates and Managed Instance Groups

An instance template is a saved set of VM settings, such as machine type, boot disk image, labels, metadata, and networking, that you can use to create VMs again and again with the same configuration. A managed instance group, or MIG, is a collection of identical VMs created from one template, with services such as autoscaling and autohealing built in.

Templates matter once you need more than one VM. Instead of filling in the same form repeatedly, and drifting slightly each time, you define the VM once. Two facts shape how you work with them. A template cannot be edited after it is created. And a group is only as good as its sizing settings, which decide how many VMs run and what you pay.

This walks through creating a template, creating a managed instance group from it, and choosing between a fixed number of VMs and autoscaling, then covers how to change a template later.

Prerequisites:

  • A Google Cloud account with billing enabled. The Enabling Billing guide in this series covers that.
  • Familiarity with creating a single VM. The Creating an Instance Using Developers Console guide in this series covers that.

Step by Step Process of Creating Instance Template

Step 1: Open Instance Templates

Open the console, Open the compute engine > Instance Templates

Step 2: Create an Instance Template

Click Create instance template.

Step 3: Fill In the Settings

The form is much like creating a single VM. Set the machine type, boot disk, networking, and anything else the VMs should have.

Step 4: Create the Template

Click Create once you have chosen the settings. The instance template is created.

Global and Regional Templates

Google Cloud has two kinds of instance template. A global template can be reused in different regions. A regional template can be used only in the region it was created in, which helps if you want to reduce cross region dependency or meet data residency rules. Either kind can be used to create VMs and managed instance groups.

Step 5: Open the Template

To create a group from the template, click the instance template in the list.

Step 6: Create an Instance Group

Click Create instance group.

Step 7: Name the Group and Choose Where It Runs

The form looks like creating a VM, but here you create several VMs with the same specification. Give the group a name, choose the location, then choose the instance template.

Step 8: Select the Template and Open Autoscaling Mode

Select the instance template you want, then open the Autoscaling mode setting. You now choose one of two paths. Pick a fixed size, or turn autoscaling on.

Option 1: A Fixed Number of Instances

Choose Don’t autoscale, then enter the number of instances you want. The group creates exactly that many VMs, and keeps that number running.

Option 2: Autoscale on CPU Utilization

If you want the group to grow and shrink, choose the autoscaling mode that adds and removes instances, then choose CPU utilization as the signal and set a target. The autoscaler compares the group’s average CPU against that target. If the average is above it, the group scales out, up to your maximum. If it is below, the group scales in, down to your minimum.

Set the Minimum and Maximum, Then Create

Enter the minimum and maximum number of instances, then click Create. With autoscaling on, the group runs between those two numbers depending on load. The original page said it creates only the specified number of instances, which is true only for the fixed size in Option One.

Autoscaling Modes and the Initialization Period

  • On, add and remove instances. The group scales both out and in.
  • Only scale out. The group can add VMs but never removes them.
  • Autoscaling is switched off, which temporarily disables it while keeping its configuration.

The cool down period is also called the initialization period. It tells the autoscaler how long your application takes to start up, so it does not judge a new VM before it is ready. The default is 60 seconds, and setting an accurate value helps the autoscaler make better decisions.

Managed and Unmanaged Instance Groups

A managed instance group is built from one instance template, so all its VMs are identical, and it supports autoscaling and autohealing. An unmanaged instance group is just a collection of VMs you add yourself, which can be different from each other, without those automated services. For anything you want to scale, use a managed group.

Changing a Template Later

Google’s documentation says instance templates are immutable, meaning they cannot be modified after they are created. To change something, create a new template with the new settings, then update the group to use it with a rolling update. Compute Engine applies the new configuration to VMs it adds, and to existing VMs according to the update policy you set. For small changes, such as metadata or labels, Google also describes an all instances configuration that overrides template properties without creating a new template.

What a Group Costs?

A group starts its VMs as soon as it is created, and each one bills like any other VM. With a fixed size you pay for that many VMs for as long as the group exists. With autoscaling, the maximum you set is the ceiling on how many VMs you could end up paying for, so choose it deliberately. Delete a practice group when you finish, which removes its VMs, and note that Compute Engine will not let you delete a template that a group is still using. The Creating and Deleting a Budget guide in this series explains why a budget alert will not stop spending for you.

Common Mistakes to Avoid

  • Treating Don’t autoscale and CPU autoscaling as steps to do one after the other. They are alternatives.
  • Trying to edit a template. Create a new one and roll it out.
  • Setting an autoscaling maximum without thinking about cost. It is your ceiling.
  • Using an unmanaged group when you need autoscaling. Only managed groups support it.
  • Leaving a practice group running after you finish.

That covers creating an instance template and a managed instance group, and choosing how it is sized. To go further, explore Prwatech’s Google Cloud training program, which includes placement assistance.

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