What causes "Failed to set registry key: %s" in juicedata/juicefs?

Re-run elevated as administrator.

Failed to set registry key: %s

Error message

Failed to set registry key: %s

What it means

After opening/creating the WinFsp service key, the code writes the service CommandLine value. If k.SetStringValue("CommandLine", cmdLine) fails, this error reports it. Values under HKLM require write access to the key.

Source

Thrown at pkg/winfsp/winfs.go:1216

func updateWinFspRegService(winfspServiceName string, cmdLine string, alias string, logPath string, asNetworkDrive bool) error {
	regKeyPath := "SOFTWARE\\WOW6432Node\\WinFsp\\Services\\" + winfspServiceName
	k, err := registry.OpenKey(registry.LOCAL_MACHINE, regKeyPath, registry.ALL_ACCESS)
	if err != nil {
		if err == syscall.ERROR_FILE_NOT_FOUND || err == syscall.ERROR_PATH_NOT_FOUND {
			logger.Info("WinFsp service registry key not found, creating it.")
			k, _, err = registry.CreateKey(registry.LOCAL_MACHINE, regKeyPath, registry.ALL_ACCESS)
			if err != nil {
				return fmt.Errorf("Failed to create registry key: %s", err)
			}
		} else {
			return fmt.Errorf("Failed to open registry key: %s", err)
		}
	}
	defer k.Close()

	err = k.SetStringValue("CommandLine", cmdLine)
	if err != nil {
		return fmt.Errorf("Failed to set registry key: %s", err)
	}

	securityDescriptor := winfspSecurityDescriptor
	err = k.SetStringValue("Security", securityDescriptor)
	if err != nil {
		return fmt.Errorf("Failed to set registry key: %s", err)
	}

	filePath, err := os.Executable()
	if err != nil {
		return fmt.Errorf("Failed to get current file path: %s", err)
	}

	err = k.SetStringValue("Executable", filePath)
	if err != nil {
		return fmt.Errorf("Failed to set registry key: %s", err)
	}

View on GitHub (pinned to c9a67b23e8)

Solutions

Re-run elevated as administrator.
Check key ACLs (KEY_SET_VALUE) for HKLM\SOFTWARE\WOW6432Node\WinFsp\Services\<service>.
Rule out security software intercepting SetStringValue on WinFsp keys.
Read the wrapped error (%s) to identify the exact Win32 code and target the fix.

Defensive patterns

Strategy: try-catch

Validate before calling

// PowerShell: verify KEY_SET_VALUE on the service key
$k = Get-Item 'HKLM:\SOFTWARE\WOW6432Node\WinFsp\Services' -ErrorAction Stop
$k.GetAccessControl('Access') | Format-Table AccessControlType,Rights,IdentityReference

Try / catch

if err := registerService(); err != nil && strings.Contains(err.Error(), "Failed to set registry key: CommandLine") {
    return fmt.Errorf("registry write denied; run elevated: %w", err)
}

Prevention

Run registration elevated so SetStringValue succeeds.
Do not let security software lock WinFsp keys.
Recreate the service key if ACLs were corrupted.
Check registry quota on constrained systems.

When it happens

Trigger: k.SetStringValue("CommandLine", cmdLine) returns an error — e.g. the handle lacks KEY_SET_VALUE access, registry quota exhausted, or the key was opened read-only by policy.

Common situations: Non-elevated runs where OpenKey succeeded via a fallback path but writes are denied; security software guarding WinFsp keys; registry size limits on constrained systems.

Related errors

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/84856f92a48130f0. Report an issue: GitHub.