kubernetes/kops · error

error rendering Instance UserData

Error message

error rendering Instance UserData: %v

What it means

Instance.RenderAWS reads the task's UserData resource fully into memory via fi.ResourceAsBytes before base64-encoding it into the RunInstances request. If reading the resource fails (unreadable file, broken resource implementation, I/O error), kOps wraps the failure as 'error rendering Instance UserData'. The instance is not created in this case.

Solutions

1. Check that the UserData source (file path or template) exists and is readable by the user running kops.
2. Run `kops update cluster --v=8` to see the underlying wrapped I/O error and fix the specific resource.
3. If using templates/assets, regenerate them (`kops create instancegroup` / update manifests) so the resource is valid.
4. Verify file permissions (chmod/chown) or copy the script into the repo and use a relative path.
5. Test rendering with a minimal inline UserData to isolate the failing resource.

Example fix

# before
kops edit cluster  # igconfig userData: file:///etc/kubernetes/bootstrap-old.sh  (file deleted)
# after
kops edit cluster  # igconfig userData: file:///etc/kubernetes/bootstrap.sh (exists, chmod 644)
kops update cluster

// Verify the UserData source is readable before running kops update
path := "/etc/kubernetes/bootstrap.sh"
f, err := os.Open(path)
if err != nil {
	return fmt.Errorf("userData source unreadable: %w", err)
}
f.Close()
// For custom fi.Resource implementations, dry-run Bytes() first
if r, ok := userDataResource.(interface{ Bytes() ([]byte, error) }); ok {
	if _, err := r.Bytes(); err != nil {
		return fmt.Errorf("userData resource fails to render: %w", err)
	}
}

err := runKopsUpdate(ctx)
if err != nil && strings.Contains(err.Error(), "error rendering Instance UserData") {
	return fmt.Errorf("check userData file paths/permissions in the cluster spec: %w", err)
}
return err

When it happens

Trigger: RunInstances-time rendering of an Instance task whose e.UserData resource cannot be read: missing file path in a file resource, permission denied, or a custom fi.Resource whose Bytes() returns an error.

Common situations: A bootstrap script path referenced in the cluster spec no longer exists or is unreadable; manifests using generated/template resources whose backing data failed to load; permission issues after running kops from a different user or container; packaging a nodeup/igconfig resource that errors on read.

Related errors

• error decoding EC2 UserData
• error decoding userdata
• Instance UserData was too large
• cannot determine challenge endpoint for instance id
• cannot revoke ingress for ID

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/6921369cb4873c3f. Report an issue: GitHub.

Appendix: source

Thrown at upup/pkg/fi/cloudup/awstasks/instance.go:272

		// Build up the actual block device mappings
		// TODO: Support RootVolumeType & RootVolumeSize (see launchconfiguration)
		blockDeviceMappings, err := buildEphemeralDevices(t.Cloud, e.InstanceType)
		if err != nil {
			return err
		}

		if len(blockDeviceMappings) != 0 {
			request.BlockDeviceMappings = []ec2types.BlockDeviceMapping{}
			for deviceName, bdm := range blockDeviceMappings {
				request.BlockDeviceMappings = append(request.BlockDeviceMappings, bdm.ToEC2(deviceName))
			}
		}

		if e.UserData != nil {
			d, err := fi.ResourceAsBytes(e.UserData)
			if err != nil {
				return fmt.Errorf("error rendering Instance UserData: %v", err)
			}
			if len(d) > MaxUserDataSize {
				// TODO: Re-enable gzip?
				// But it exposes some bugs in the AWS console, so if we can avoid it, we should
				//d, err = fi.GzipBytes(d)
				//if err != nil {
				//	return fmt.Errorf("error while gzipping UserData: %v", err)
				//}
				return fmt.Errorf("Instance UserData was too large (%d bytes)", len(d))
			}
			request.UserData = aws.String(base64.StdEncoding.EncodeToString(d))
		}

		if e.IAMInstanceProfile != nil {
			request.IamInstanceProfile = &ec2types.IamInstanceProfileSpecification{
				Name: e.IAMInstanceProfile.Name,
			}
		}

View on GitHub (pinned to 4c8573c808)