kubernetes/kops · error

error assigning default machine type for bastions

Error message

error assigning default machine type for bastions: %v

What it means

Same defaulting path as the control-plane case, but for bastion instance groups: if a bastion group has no machine type, kops calls defaultMachineType() and wraps any failure with this message. Cluster creation aborts before any infrastructure is built.

Solutions

1. Set an explicit bastion machine type: `--bastion-size=t3.micro` (AWS) or set spec.machineType on the bastion instance group.
2. Inspect the wrapped underlying error and address the cloud API cause.
3. Re-run after verifying credentials/region support for the default family.

Example fix

// before
kops create cluster --name=example.com --bastion
// after
kops create cluster --name=example.com --bastion --bastion-size=t3.micro

if bastionIG != nil && bastionIG.Spec.MachineType == "" {
    bastionIG.Spec.MachineType = "t3.micro"
}

_, err := NewCluster(opt, cluster, zoneMap)
if err != nil {
    if strings.Contains(err.Error(), "default machine type for bastions") {
        return fmt.Errorf("set --bastion-size explicitly or fix cloud API access: %w", err)
    }
    return err
}

When it happens

Trigger: Creating a cluster with a bastion group (`--bastion` or explicit bastion IG) with no machine type set while the cloud lookup fails — API error, unsupported region, insufficient credentials.

Common situations: `kops create cluster --bastion` in a region where the default instance family is unavailable; cloud API throttling or connectivity issues; IAM policy too restrictive to describe instance types.

Related errors

• error assigning default machine type for control plane
• error assigning default machine type for nodes
• adding key to SSH agent
• error assigning default machine type for nodes
• error finding default machine type

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/181c8880c376714b. Report an issue: GitHub.

Appendix: source

Thrown at upup/pkg/fi/cloudup/new_cluster.go:536

					return nil, err
				}
			}
		}

		// TODO: Clean up
		if g.IsControlPlane() {
			if g.Spec.MachineType == "" {
				g.Spec.MachineType, err = defaultMachineType(cloud, cluster, ig)
				if err != nil {
					return nil, fmt.Errorf("error assigning default machine type for control plane: %v", err)
				}

			}
		} else if g.Spec.Role.HasBastion() {
			if g.Spec.MachineType == "" {
				g.Spec.MachineType, err = defaultMachineType(cloud, cluster, g)
				if err != nil {
					return nil, fmt.Errorf("error assigning default machine type for bastions: %v", err)
				}
			}
		} else {
			if g.IsAPIServerOnly() && !featureflag.APIServerNodes.Enabled() {
				return nil, fmt.Errorf("apiserver nodes requires the APIServerNodes feature flag to be enabled")
			}
			if !featureflag.ExperimentalRoles.Enabled() {
				switch {
				case g.Spec.Role.HasEtcd():
					return nil, fmt.Errorf("etcd nodes requires the ExperimentalRoles feature flag to be enabled")
				case g.Spec.Role.HasScheduler():
					return nil, fmt.Errorf("scheduler nodes requires the ExperimentalRoles feature flag to be enabled")
				case g.Spec.Role.HasKubeControllerManager():
					return nil, fmt.Errorf("kube-controller-manager nodes requires the ExperimentalRoles feature flag to be enabled")
				}
			}
			if g.Spec.MachineType == "" {
				g.Spec.MachineType, err = defaultMachineType(cloud, cluster, g)

View on GitHub (pinned to 4c8573c808)