docker/cli · error

%s is not a valid domain

Error message

%s is not a valid domain

What it means

Error "%s is not a valid domain" thrown in docker/cli.

Source

Thrown at opts/opts.go:217

	_, err := net.ParseMAC(strings.TrimSpace(val))
	if err != nil {
		return "", err
	}
	return val, nil
}

// ValidateDNSSearch validates domain for resolvconf search configuration.
// A zero length domain is represented by a dot (.).
func ValidateDNSSearch(val string) (string, error) {
	if val = strings.Trim(val, " "); val == "." {
		return val, nil
	}
	return validateDomain(val)
}

func validateDomain(val string) (string, error) {
	if alphaRegexp.FindString(val) == "" {
		return "", fmt.Errorf("%s is not a valid domain", val)
	}
	ns := domainRegexp.FindSubmatch([]byte(val))
	if len(ns) > 0 && len(ns[1]) < 255 {
		return string(ns[1]), nil
	}
	return "", fmt.Errorf("%s is not a valid domain", val)
}

const whiteSpaces = " \t"

// ValidateLabel validates that the specified string is a valid label, and returns it.
//
// Labels are in the form of key=value; key must be a non-empty string, and not
// contain whitespaces. A value is optional (defaults to an empty string if omitted).
//
// Leading whitespace is removed during validation but values are kept as-is
// otherwise, so any string value is accepted for both, which includes whitespace
// (for values) and quotes (surrounding, or embedded in key or value).

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at opts/opts.go:217 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/0c6f99b40eb4dea0.json. Report an issue: GitHub.