kubernetes/kubernetes · error

the argument must have both a key and a value

Error message

the argument must have both a key and a value

What it means

Returned by parseArgument when, after stripping '--' and splitting on '=' with SplitN(.,=,2), the result does not yield exactly two parts. In practice this is guarded by the earlier '=' presence check, so it covers an edge-case where splitting still fails to produce a key/value pair.

Source

Thrown at cmd/kubeadm/app/util/arguments.go:105

	return args
}

// parseArgument parses the argument "--foo=bar" to "foo" and "bar"
func parseArgument(arg string) (string, string, error) {
	if !strings.HasPrefix(arg, "--") {
		return "", "", errors.New("the argument should start with '--'")
	}
	if !strings.Contains(arg, "=") {
		return "", "", errors.New("the argument should have a '=' between the flag and the value")
	}
	// Remove the starting --
	arg = strings.TrimPrefix(arg, "--")
	// Split the string on =. Return only two substrings, since we want only key/value, but the value can include '=' as well
	keyvalSlice := strings.SplitN(arg, "=", 2)

	// Make sure both a key and value is present
	if len(keyvalSlice) != 2 {
		return "", "", errors.New("the argument must have both a key and a value")
	}
	if len(keyvalSlice[0]) == 0 {
		return "", "", errors.New("the argument must have a key")
	}

	return keyvalSlice[0], keyvalSlice[1], nil
}

// sortArgsSlice sorts a slice of Args alpha-numerically.
func sortArgsSlice(argsPtr *[]kubeadmapi.Arg) {
	args := *argsPtr
	sort.Slice(args, func(i, j int) bool {
		if args[i].Name == args[j].Name {
			return args[i].Value < args[j].Value
		}
		return args[i].Name < args[j].Name
	})
}

View on GitHub (pinned to b882c60b40)

Solutions

1. Rewrite the token in canonical '--key=value' form.
2. Remove stray characters/whitespace around the '=' in kubeadm-flags.env or extraArgs.
3. If reproducing, isolate the exact token and report it; this branch is defensive and seldom reached.

Example fix

# before (malformed token)
KUBELET_KUBEADM_ARGS="--=value"
# after
KUBELET_KUBEADM_ARGS="--real-key=value"

parts := strings.SplitN(strings.TrimPrefix(a, "--"), "=", 2)
if len(parts) != 2 {
    return fmt.Errorf("argument %q must have both key and value", a)
}

func isKeyValuePair(a string) bool {
    parts := strings.SplitN(strings.TrimPrefix(a, "--"), "=", 2)
    return len(parts) == 2
}

When it happens

Trigger: A token that passes the '--' prefix and '=' presence checks but SplitN(arg,'=',2) returns something other than two elements (defensive branch; rarely hit given the prior checks).

Common situations: Extremely unusual inputs; effectively a defensive guard. If hit, the token is structurally malformed despite containing '='.

Related errors

• the argument should start with '--'
• the argument should have a '=' between the flag and the valu
• the argument must have a key
• the --old-config flag is mandatory
• cannot use --certificate-key without --print-join-command

AI-assisted analysis of kubernetes/kubernetes@b882c60b40 (2026-08-07). Data as JSON: /api/errors/a6507474094fe53e. Report an issue: GitHub.