henrygd/beszel · error

failed to create temp directory: %w

Error message

failed to create temp directory: %w

What it means

On Windows the agent's LibreHardwareMonitor (LHM) helper requires copying its embedded executable to a temp directory; this error wraps an os.MkdirAll failure for %TEMP%\beszel. It indicates the temp directory could not be created — filesystem or permission problem — so no sensor data can be collected via LHM.

Source

Thrown at agent/sensors_windows.go:60

//go:embed all:lhm/bin/Release/net48
var lhmFs embed.FS

var (
	beszelLhm     *lhmProcess
	beszelLhmOnce sync.Once
	useLHM        = os.Getenv("LHM") == "true"
)

var errNoSensors = errors.New("no sensors found (try running as admin with LHM=true)")

// newlhmProcess copies the embedded LHM executable to a temporary directory and starts it.
func newlhmProcess() (*lhmProcess, error) {
	destDir := filepath.Join(os.TempDir(), "beszel")
	execPath := filepath.Join(destDir, "beszel_lhm.exe")

	if err := os.MkdirAll(destDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create temp directory: %w", err)
	}

	// Only copy if executable doesn't exist
	if _, err := os.Stat(execPath); os.IsNotExist(err) {
		if err := copyEmbeddedDir(lhmFs, "lhm/bin/Release/net48", destDir); err != nil {
			return nil, fmt.Errorf("failed to copy embedded directory: %w", err)
		}
	}

	lhm := &lhmProcess{
		execPath: execPath,
		tempDir:  destDir,
	}

	if err := lhm.startProcess(); err != nil {
		return nil, fmt.Errorf("failed to start process: %w", err)
	}

View on GitHub (pinned to b38fb7dafa)

Solutions

1. Check TEMP/TMP env vars for the account running the agent and ensure the path exists and is writable.
2. Free disk space if the volume holding %TEMP% is full.
3. Run the agent service under an account with write permission to its temp directory, or set TEMP to a dedicated writable folder.
4. Exclude the beszel temp dir from antivirus/temp-cleaner policies that delete it.
5. Create the directory manually (mkdir %TEMP%\beszel) and re-run to confirm permissions.

Example fix

// before (service env)
TEMP=C:\Windows\Temp  # service account lacks write access
// after
set TEMP=C:\beszel\tmp  (grant the service account Modify on it)

// before starting LHM helper:
if err := os.MkdirAll(filepath.Join(os.TempDir(), "beszel"), 0755); err != nil {
    return fmt.Errorf("temp dir unusable: %w", err)
}

proc, err := newlhmProcess()
if err != nil {
    if strings.Contains(err.Error(), "failed to create temp directory") {
        slog.Warn("LHM unavailable: temp dir not writable", "err", err)
        return nil // run without LHM sensor data
    }
    return err
}

When it happens

Trigger: newlhmProcess() builds destDir = os.TempDir()+"beszel" and calls os.MkdirAll(destDir, 0755); failure (ENOENT parent gone, EPERM, disk full, path redirected to a read-only location) wraps the OS error.

Common situations: TEMP/TMP env var pointing at a missing, read-only, or network path; enterprise policy restricting executable creation in temp; disk full; temp cleaner service removing the directory mid-run; agent running as a service account without write access to its temp dir.

Related errors

• no sensors found (try running as admin with LHM=true)
• failed to create smartctl directory: %w
• failed to write embedded smartctl: %w
• battery tag not returned
• battery capacity unknown

AI-assisted analysis of henrygd/beszel@b38fb7dafa (2026-08-31). Data as JSON: /api/errors/b792385e412fe523. Report an issue: GitHub.