docker/cli · error

unknown server OS: %s

Error message

unknown server OS: %s

What it means

Error "unknown server OS: %s" thrown in docker/cli.

Source

Thrown at cli/command/container/opts.go:1003

		k, v, ok := strings.Cut(option, "=")
		if !ok {
			return nil, errors.New("invalid storage option")
		}
		m[k] = v
	}
	return m, nil
}

// parseDevice parses a device mapping string to a container.DeviceMapping struct
func parseDevice(device, serverOS string) (container.DeviceMapping, error) {
	switch serverOS {
	case "linux":
		return parseLinuxDevice(device)
	case "windows":
		// Windows doesn't support mapping, so passing the given value as-is.
		return container.DeviceMapping{PathOnHost: device}, nil
	default:
		return container.DeviceMapping{}, fmt.Errorf("unknown server OS: %s", serverOS)
	}
}

// parseLinuxDevice parses a device mapping string to a container.DeviceMapping struct
// knowing that the target is a Linux daemon
func parseLinuxDevice(device string) (container.DeviceMapping, error) {
	var src, dst string
	permissions := "rwm"
	// We expect 3 parts at maximum; limit to 4 parts to detect invalid options.
	arr := strings.SplitN(device, ":", 4)
	switch len(arr) {
	case 3:
		permissions = arr[2]
		fallthrough
	case 2:
		if validDeviceMode(arr[1]) {
			permissions = arr[1]
		} else {

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cli/command/container/opts.go:1003 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/0332a1d6acf7a3c8.json. Report an issue: GitHub.