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

Re-run the mount command from an elevated (Run as administrator) prompt.

Failed to create registry key: %s

Error message

Failed to create registry key: %s

What it means

updateWinFspRegService registers the WinFsp launcher service under HKLM\SOFTWARE\WOW6432Node\WinFsp\Services. When the key is absent it tries to create it; if registry.CreateKey fails, this error reports the failure. Creating the key requires write access to HKLM, typically administrator rights.

Source

Thrown at pkg/winfsp/winfs.go:1206

	exitOk := host.Mount(conf.Mountpoint, []string{"-o", options})
	if exitOk {
		return nil
	}

	return fmt.Errorf("juicefs mount command exit with error, please check the log for details")
}

const winfspSecurityDescriptor = "D:P(A;;RPWPLC;;;WD)"

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)
	}

View on GitHub (pinned to c9a67b23e8)

Solutions

Re-run the mount command from an elevated (Run as administrator) prompt.
If run as a Windows service, grant the service account write access to the WinFsp Services registry key.
Check Group Policy or security software blocking HKLM writes.
Verify the underlying error string; ERROR_ACCESS_DENIED confirms a permissions fix is the right path.

Example fix

// shell
# before (non-elevated)
juicefs mount sqlite3://test.db Z:
# after
# open an elevated PowerShell, then
juicefs mount sqlite3://test.db Z:

Defensive patterns

Strategy: try-catch

Validate before calling

// PowerShell: verify HKLM write access before registering the service
$k = [Microsoft.Win32.RegistryKey]::OpenBaseKey('LocalMachine','Registry32')
try { $t = $k.CreateSubKey('SOFTWARE\WOW6432Node\WinFsp\Services\juicefs-test'); $t.Close() }
catch { throw 'No HKLM write access; run elevated' }

Try / catch

if err := mount(); err != nil && strings.Contains(err.Error(), "Failed to create registry key") {
    return fmt.Errorf("run as administrator to register the WinFsp service: %w", err)
}

Prevention

Run service registration from an elevated shell.
Grant service accounts HKLM write access when automating.
Check Group Policy restrictions on registry writes.
Test registry permissions as part of deployment preflight.

When it happens

Trigger: Running registry.CreateKey(LOCAL_MACHINE, regKeyPath, ALL_ACCESS) and receiving a non-nil error — usually ERROR_ACCESS_DENIED from a non-elevated process, or registry virtualization/policy restrictions.

Common situations: Running `juicefs mount` from a non-admin shell or service account without HKLM write permission; Group Policy restricting registry writes; antivirus blocking registry modification.

Related errors

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/bbfcb7fd823506e8. Report an issue: GitHub.