cloudflare/cloudflared · error

expected system information to have %d fields got %d: %w

Error message

expected system information to have %d fields got %d: %w

What it means

ParseUnameOutput parses `uname -a` output and requires at least `osInformationFieldsMinimum` whitespace-separated fields to derive system, hostname, and architecture. If the uname output is too short, it returns ErrInsuficientFields wrapped in this message. On darwin an architectureOffset of 1 shifts the architecture field index because macOS uname output has a different shape.

Source

Thrown at diagnostic/system_collector_utils.go:142

func ParseUnameOutput(output string, system string) (*OsInfo, error) {
	const (
		osystemField               = 0
		nameField                  = 1
		osVersionField             = 2
		osReleaseStartField        = 3
		osInformationFieldsMinimum = 6
		darwin                     = "darwin"
	)

	architectureOffset := 2
	if system == darwin {
		architectureOffset = 1
	}

	fields := strings.Fields(output)
	if len(fields) < osInformationFieldsMinimum {
		return nil, fmt.Errorf("expected system information to have %d fields got %d: %w",
			osInformationFieldsMinimum, len(fields), ErrInsuficientFields,
		)
	}

	architectureField := len(fields) - architectureOffset
	osystem := fields[osystemField]
	name := fields[nameField]
	osVersion := fields[osVersionField]
	osRelease := strings.Join(fields[osReleaseStartField:architectureField], " ")
	architecture := fields[architectureField]

	return &OsInfo{
		osystem,
		name,
		osVersion,
		osRelease,
		architecture,
	}, nil

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Ensure the collector invokes `uname -a` (all fields) and capture stderr to confirm the command succeeded before parsing.
2. Verify `uname -a` output manually on the affected host; if it is truncated, fix the host environment or uname binary.
3. Guard the caller against empty output (skip parsing when strings.TrimSpace(output) is empty).
4. On darwin hosts confirm the darwin-specific architectureOffset path matches the actual uname format for the OS version.

Example fix

// before
out, _ := exec.Command("uname").Output()
info, err := diagnostic.ParseUnameOutput(string(out))
// after
out, err := exec.Command("uname", "-a").Output()
if err != nil {
	return err
}
if len(strings.Fields(string(out))) < 3 {
	return fmt.Errorf("uname output too short: %q", string(out))
}
info, err := diagnostic.ParseUnameOutput(string(out))

func validateUnameOutput(output string) error {
	fields := strings.Fields(output)
	if len(fields) < 3 {
		return fmt.Errorf("uname output too short (%d fields): %q", len(fields), output)
	}
	return nil
}

info, err := diagnostic.ParseUnameOutput(unameOut)
var target error = diagnostic.ErrInsuficientFields
if errors.Is(err, target) {
	log.Warn().Str("output", unameOut).Msg("uname output malformed; skipping OS info")
} else if err != nil {
	return fmt.Errorf("uname parse failed: %w", err)
}

When it happens

Trigger: Calling ParseUnameOutput (directly or via collectOSInformationUnix during Collect) with empty, truncated, or stubbed `uname -a` output — e.g. uname failing partially, a mock/minimal environment printing nothing, or capturing only part of the output.

Common situations: Minimal containers with a stub uname, calling uname without the -a flag so output lacks fields, trailing-newline-only output on broken hosts, or feeding output from a different command (e.g. plain `uname`) into the parser.

Related errors

• parsing os information: %w, key=%s
• ErrInsufficientLines
• ErrInsuficientFields
• ErrKeyNotFound
• ErrEmptyDomain

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/cf8732afc8ea9db7. Report an issue: GitHub.