lima-vm/lima · error

sysctl: unimplemented on Windows

Error message

sysctl: unimplemented on Windows

What it means

The Windows build of osutil.Sysctl is a stub that always returns this error, since Windows has no sysctl interface (that's a BSD/macOS kernel API). It exists to keep the cross-platform Sysctl function signature compilable on Windows.

Source

Thrown at pkg/osutil/osutil_windows.go:76

}

func Dup2(_ int, _ syscall.Handle) error {
	return errors.New("unimplemented")
}

func SignalName(sig os.Signal) string {
	switch sig {
	case syscall.SIGINT:
		return "SIGINT"
	case syscall.SIGTERM:
		return "SIGTERM"
	default:
		return fmt.Sprintf("Signal(%d)", sig)
	}
}

func Sysctl(_ context.Context, _ string) (string, error) {
	return "", errors.New("sysctl: unimplemented on Windows")
}

func IsEACCES(err error) bool {
	return errors.Is(err, syscall.ERROR_ACCESS_DENIED) || errors.Is(err, syscall.WSAEACCES)
}

View on GitHub (pinned to dd909d0973)

Solutions

1. Gate sysctl reads behind runtime.GOOS checks and use the Windows registry / GetSystemInfo / WMI equivalents on Windows.
2. For kernel version info on Windows use golang.org/x/sys/windows RtlGetVersion instead of Sysctl.
3. Handle the error gracefully with a platform-appropriate default value.

Example fix

// before
v, err := osutil.Sysctl(ctx, "kern.osrelease")
// after
if runtime.GOOS == "windows" {
    v = windowsKernelVersion() // RtlGetVersion
} else {
    v, err = osutil.Sysctl(ctx, "kern.osrelease")
}

if runtime.GOOS == "windows" {
    // Sysctl always errors here; obtain the value via registry/WMI/RtlGetVersion instead
}

func sysctlSupported() bool { return runtime.GOOS == "linux" || runtime.GOOS == "darwin" }

v, err := osutil.Sysctl(ctx, name)
if err != nil && strings.Contains(err.Error(), "unimplemented on Windows") {
    v = windowsEquivalent(name) // registry/WMI fallback
}

When it happens

Trigger: Any call to osutil.Sysctl(ctx, name) on a Windows build unconditionally returns errors.New("sysctl: unimplemented on Windows") — there is no successful path.

Common situations: Shared code that reads kernel parameters via sysctl (e.g. detecting cgroup limits or kernel versions) running on a Windows host; cross-platform tooling developed on Linux/macOS then run on Windows.

Related errors

• unimplemented
• unimplemented
• unimplemented
• --condition=boot is only supported on macOS
• failed to register instance %#q to start at login: %w

AI-assisted analysis of lima-vm/lima@dd909d0973 (2026-09-01). Data as JSON: /api/errors/3b2b918bfa8495df. Report an issue: GitHub.