How to customize a template's image and flavor

Change the operating system image or hardware size on an OpenTofu template you already deployed. This guide applies to any template under Automation templates that exposes image_name and flavor variables in variables.tf. Image and flavor names must match Quake AI catalog literals; see Authoring IaC templates for Quake AI for the full naming rules and template conventions.

Locate the image and flavor variables#

Open variables.tf in your template directory. Every compute-backed template declares an image_name variable and at least one flavor variable. The flavor variable name differs by template:

The simple-vm template wires these variables into a Glance data source and the instance resource:

data "openstack_images_image_v2" "os" {
  name        = var.image_name
  most_recent = true
}

resource "openstack_compute_instance_v2" "vm" {
  flavor_name = var.flavor_name
  # ...
  block_device {
    uuid = data.openstack_images_image_v2.os.id
    # ...
  }
}

The wordpress-mysql template uses one shared image_name for both instances but separate flavor variables:

resource "openstack_compute_instance_v2" "wordpress" {
  flavor_name = var.wp_flavor
  # ...
}

resource "openstack_compute_instance_v2" "mysql" {
  flavor_name = var.db_flavor
  # ...
}

Templates look up images by name, so the value you set must match a Glance image name exactly (for example Ubuntu-24.04, not Ubuntu 24.04).

Choose an image and flavor#

Set the new image or flavor#

Pick one override mechanism. Use the same approach for every subsequent change so your team knows where values live.

Option A: terraform.tfvars (recommended)#

Create or edit terraform.tfvars in the template directory:

image_name  = "Rocky-9"
flavor_name = "c2a.large"

For wordpress-mysql:

image_name = "Ubuntu-22.04"
wp_flavor  = "s1a.medium"
db_flavor  = "m2a.large"

OpenTofu loads terraform.tfvars automatically on every plan and apply.

Option B: -var on the command line#

tofu plan \
  -var 'image_name=Rocky-9' \
  -var 'flavor_name=c2a.large'

Repeat each -var flag for every flavor variable your template defines.

Option C: edit the default in variables.tf#

Change the default attribute on the variable block. This works for a personal fork but makes upstream merges harder, so prefer terraform.tfvars for values you change often.

Plan and apply the change#

From the template directory:

tofu plan
tofu apply

Read the plan carefully:

• Image change: OpenTofu marks affected openstack_compute_instance_v2 resources with -/+ or forces replacement because the boot volume is rebuilt from the new Glance image. Plan for brief downtime and a new root volume.
• Flavor change: A larger flavor usually updates in place. Downgrading RAM may require replacement depending on the instance state; the plan output shows forces replacement when OpenTofu cannot resize in place.

If the plan fails with Your query returned no results, the image or flavor name does not match the catalog. Re-run openstack image list or openstack flavor list and copy the name exactly.

Verify the new image and flavor#

After tofu apply completes, confirm the running instances match your overrides.

openstack server list -f table -c Name -c Flavor -c Image

For a single instance:

openstack server show INSTANCE_NAME -c flavor -c image -f yaml

If the template exposes addresses in outputs.tf (as simple-vm does), retrieve them with:

tofu output

SSH to the instance and check the OS when you changed image_name. Replace YOUR_USER with the default SSH user for your image. See default usernames by distribution.

ssh -i ~/.ssh/YOUR_KEY YOUR_USER@FLOATING_IP cat /etc/os-release

See also#

• Authoring IaC templates for Quake AI
• Automation templates: reference pages for all 13 templates
• Flavors: category overview and sizing guidance
• Images CLI reference: full openstack image command set
• Flavors CLI reference: full openstack flavor command set
• How to manage multiple environments with OpenTofu: per-environment tfvars files
• How to debug Terraform errors: data-source name mismatches and quota errors