kubernetes/kops · error

error building kubelet config

Error message

error building kubelet config: %v

What it means

KubeletBuilder.Build wraps failures from buildKubeletConfigSpec, which derives the effective kubelet configuration (InstanceGroup/cluster spec merged with feature gates, flags, etc.). Any error computing that spec aborts building the kubelet model.

Solutions

1. Inspect the wrapped inner error to find which kubelet config field failed.
2. Validate the cluster spec with `kops replace --dry-run` / `kops get cluster -o yaml` review for invalid kubelet settings.
3. Fix or remove invalid kubelet config values in the cluster or InstanceGroup spec.
4. Re-run kops update cluster to regenerate the manifest, then retry nodeup.

Example fix

// before (invalid kubelet spec)
kubelet:
  maxPods: not-a-number
// after
kubelet:
  maxPods: 110

// validate kubelet spec fields before apply
if c.Spec.Kubelet != nil && c.Spec.Kubelet.MaxPods != nil && *c.Spec.Kubelet.MaxPods <= 0 {
    return errors.New("kubelet.maxPods must be positive")
}
// kubectl dry-run
// kops replace -f cluster.yaml --dry-run

When it happens

Trigger: buildKubeletConfigSpec returns an error while merging cluster/instancegroup kubelet config — e.g. invalid kubelet config values in the cluster spec, unsupported fields, or missing context/cluster data.

Common situations: Malformed kops cluster spec (bad kubelet config block, invalid feature gates or eviction settings), instance groups referencing a kubelet config that cannot be resolved.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• building
• CacheDir is required
• cannot parse ConfigBase
• ConfigBase or ConfigServer is required
• ConfigLocation is required

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/e61e1072aca4ecbe. Report an issue: GitHub.

Appendix: source

Thrown at nodeup/pkg/model/kubelet.go:112

// KubeletBuilder installs kubelet
type KubeletBuilder struct {
	*NodeupModelContext
}

var _ fi.NodeupModelBuilder = &KubeletBuilder{}

// Build is responsible for building the kubelet configuration
func (b *KubeletBuilder) Build(c *fi.NodeupModelBuilderContext) error {
	err := b.buildKubeletServingCertificate(c)
	if err != nil {
		return fmt.Errorf("error building kubelet server cert: %v", err)
	}

	ctx := c.Context()
	kubeletConfig, err := b.buildKubeletConfigSpec(ctx)
	if err != nil {
		return fmt.Errorf("error building kubelet config: %v", err)
	}

	{
		// Set the provider ID to help speed node registration on large clusters
		var providerID string
		if b.CloudProvider() == kops.CloudProviderAWS {
			config, err := awsconfig.LoadDefaultConfig(ctx)
			if err != nil {
				return fmt.Errorf("error loading AWS config: %v", err)
			}
			metadata := imds.NewFromConfig(config)
			instanceIdentity, err := metadata.GetInstanceIdentityDocument(ctx, &imds.GetInstanceIdentityDocumentInput{})
			if err != nil {
				return err
			}
			providerID = fmt.Sprintf("aws:///%s/%s", instanceIdentity.AvailabilityZone, instanceIdentity.InstanceID)
		} else if b.CloudProvider() == kops.CloudProviderAzure {
			metadata, err := azuremetadata.QueryComputeInstanceMetadata(ctx)

View on GitHub (pinned to 4c8573c808)