cloudflare/cloudflared · error

ErrCreatingTemporaryFile

ErrCreatingTemporaryFile

Error message

temporary file creation failed

What it means

ErrCreatingTemporaryFile is returned by diagnostic procedures (collectLogs, rawNetworkInformationWriter, jsonNetworkInformationWriter, createTaskReport) when os.Create on a file in os.TempDir() fails. The diagnostic pipeline writes logs, network dumps, and task reports to temporary files before zipping them; if that creation fails the diagnostic cannot proceed. The original os error is discarded, so only the sentinel is visible.

Source

Thrown at diagnostic/error.go:27

	ErrManagedLogNotFound = errors.New("managed log directory not found")
	// Error used when it is not possible to collect logs using the log configuration.
	ErrLogConfigurationIsInvalid = errors.New("provided log configuration is invalid")
	// Error used when parsing the fields of the output of collector.
	ErrInsufficientLines = errors.New("insufficient lines")
	// Error used when parsing the lines of the output of collector.
	ErrInsuficientFields = errors.New("insufficient fields")
	// Error used when given key is not found while parsing KV.
	ErrKeyNotFound = errors.New("key not found")
	// Error used when there is no disk volume information available.
	ErrNoVolumeFound = errors.New("no disk volume information found")
	// Error user when the base url of the diagnostic client is not provided.
	ErrNoBaseURL = errors.New("no base url")
	// Error used when no metrics server is found listening to the known addresses list (check [metrics.GetMetricsKnownAddresses]).
	ErrMetricsServerNotFound = errors.New("metrics server not found")
	// Error used when multiple metrics server are found listening to the known addresses list (check [metrics.GetMetricsKnownAddresses]).
	ErrMultipleMetricsServerFound = errors.New("multiple metrics server found")
	// Error used when a temporary file creation fails within the diagnostic procedure
	ErrCreatingTemporaryFile = errors.New("temporary file creation failed")
)

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Check that os.TempDir() (or $TMPDIR) exists and is writable by the user running cloudflared.
2. Free disk space on the volume holding the temp directory.
3. Remove any conflicting file/directory at the temp path the diagnostic writes to.
4. Set TMPDIR to a writable location before launching the diagnostic.

Example fix

// before
outputLogHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
if err != nil {
	return "", ErrCreatingTemporaryFile
}
// after
outputLogHandle, err := os.Create(filepath.Join(os.TempDir(), logFilename))
if err != nil {
	return "", fmt.Errorf("%w: %v", ErrCreatingTemporaryFile, err)
}

tmp := os.TempDir()
if fi, err := os.Stat(tmp); err != nil || !fi.IsDir() {
	return errors.New("temp directory unavailable")
}
if f, err := os.CreateTemp(tmp, "cfd-diag-*"); err != nil {
	return fmt.Errorf("temp dir not writable: %w", err)
} else {
	f.Close()
	os.Remove(f.Name())
}

out, err := diagnostic.RunDiagnostic(log, options)
if errors.Is(err, diagnostic.ErrCreatingTemporaryFile) {
	return fmt.Errorf("diagnostic failed: cannot write to %s: %w", os.TempDir(), err)
}

When it happens

Trigger: os.Create(filepath.Join(os.TempDir(), ...)) failing at diagnostic/diagnostic.go:140 (output log), diagnostic/diagnostic.go:242 (raw network dump), and in the JSON network writer and createTaskReport paths — e.g. unwritable TMPDIR, full disk, or the path existing as a directory.

Common situations: Read-only or full /tmp, TMPDIR pointing to a non-existent or permission-restricted directory, running under a sandboxed service account with no write access to the temp directory, or a stale file/dir collision at the target name.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• creating temporary log file %s: %w
• the argument path must be a directory
• cloudflared service is already installed at %s; if you are r
• The file-writing error is: %v / The delete tunnel error is:
• ErrManagedLogNotFound

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/b3c590b7041a7b87. Report an issue: GitHub.