kubernetes/kops · error

couldn't determine hostname: %w

Error message

couldn't determine hostname: %w

What it means

os.Hostname() failed while building a file-based PKI authenticator: the kernel returned an error for gethostname, so the instance identity embedded in auth tokens cannot be determined. The path/key-file arguments are only processed after this.

Source

Thrown at pkg/bootstrap/pkibootstrap/pkisigner.go:89

func computeKeyID(signer crypto.Signer) (string, error) {
	publicKey := signer.Public()
	pkData, err := x509.MarshalPKIXPublicKey(publicKey)
	if err != nil {
		return "", fmt.Errorf("error converting public key to x509: %w", err)
	}

	var b bytes.Buffer
	if err := pem.Encode(&b, &pem.Block{Type: "PUBLIC KEY", Bytes: pkData}); err != nil {
		return "", fmt.Errorf("error encoding public key: %w", err)
	}
	return b.String(), nil
}

func NewAuthenticatorFromFile(p string) (bootstrap.Authenticator, error) {
	hostname, err := os.Hostname()
	if err != nil {
		return nil, fmt.Errorf("couldn't determine hostname: %w", err)
	}

	keyBytes, err := os.ReadFile(p)
	if err != nil {
		return nil, fmt.Errorf("error reading %q: %w", p, err)
	}
	key, err := pki.ParsePEMPrivateKey(keyBytes)
	if err != nil {
		return nil, fmt.Errorf("error parsing key from %q: %w", p, err)
	}

	return NewAuthenticator(hostname, key.Key)
}

func (a *pkiAuthenticator) CreateToken(body []byte) (string, error) {
	requestHash := sha256.Sum256(body)

	data := AuthTokenData{

View on GitHub (pinned to 4c8573c808)

Solutions

1. Investigate why the node's hostname is unobtainable (UTS namespace or container sandbox restrictions)
2. Set a valid hostname on the host and retry
3. If running in a constrained container, ensure the sandbox permits hostname syscalls

When it happens

Trigger: Thrown at pkg/bootstrap/pkibootstrap/pkisigner.go:89 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/8e1addd87c01b458. Report an issue: GitHub.