prometheus/node_exporter · error

failed to parse /proc/net/dev

Error message

failed to parse /proc/net/dev: %w

What it means

After opening procfs, procNetDevStats calls fs.NetDev() to parse /proc/net/dev. If parsing fails (unexpected file content or format), the error is wrapped as 'failed to parse /proc/net/dev'. procfs expects the kernel's documented net/dev format, so a parse failure signals either a non-standard kernel or that the path points at something that is not a real /proc/net/dev.

Solutions

1. Verify cat /host/proc/net/dev (or your configured path) shows the standard two-header-line format with rx/tx columns.
2. Confirm the mount is genuine host procfs, not a copied/overlay directory.
3. Upgrade node_exporter/procfs library, then retry — parser tolerance changes between releases.
4. Inspect the wrapped inner error to see the line or field that failed to parse.
5. If running under gVisor/LXC, test the same collector on plain Linux to confirm the environment is the cause.

// preflight: file must look like kernel /proc/net/dev
b, err := os.ReadFile(filepath.Join(*procPath, "net", "dev"))
if err != nil { return err }
lines := strings.Split(string(b), "\n")
if len(lines) < 3 || !strings.Contains(lines[0], "bytes") || !strings.Contains(lines[1], "packets") {
	return fmt.Errorf("%s/net/dev has unexpected format", *procPath)
}

err := collector.Update(ch)
if err != nil && strings.Contains(err.Error(), "failed to parse /proc/net/dev") {
	logger.Error("procfs parse failed; environment likely non-standard (gVisor/LXC?)", "err", err)
	return nil
}

When it happens

Trigger: fs.NetDev() errors while scanning/parsing /proc/net/dev: file missing under the mounted procfs, malformed lines (custom kernels, virtualized /proc shims), or read errors mid-parse.

Common situations: --path.procfs pointing at a fake/overlay directory that contains a partial /proc copy; LXC/gVisor environments presenting unusual /proc/net/dev contents; procfs library version incompatibility with unusual kernel output.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• interrupts empty
• ZFS / ZFS statistics are not available
• failed to open procfs
• failed to open procfs
• couldn't get buddyinfo

AI-assisted analysis of prometheus/node_exporter@17ddd77c59 (2026-09-07). Data as JSON: /api/errors/b5fc44f5ae340d6d. Report an issue: GitHub.

Appendix: source

Thrown at collector/netdev_linux.go:154

			"transmit_compressed": stats.TXCompressed,
			"receive_nohandler":   stats.RXNoHandler,
		}
	}

	return metrics
}

func procNetDevStats(filter *deviceFilter, logger *slog.Logger) (netDevStats, error) {
	metrics := netDevStats{}

	fs, err := procfs.NewFS(*procPath)
	if err != nil {
		return metrics, fmt.Errorf("failed to open procfs: %w", err)
	}

	netDev, err := fs.NetDev()
	if err != nil {
		return metrics, fmt.Errorf("failed to parse /proc/net/dev: %w", err)
	}

	for _, stats := range netDev {
		name := stats.Name

		if filter.ignored(name) {
			logger.Debug("Ignoring device", "device", name)
			continue
		}

		metrics[name] = map[string]uint64{
			"receive_bytes":       stats.RxBytes,
			"receive_packets":     stats.RxPackets,
			"receive_errors":      stats.RxErrors,
			"receive_dropped":     stats.RxDropped,
			"receive_fifo":        stats.RxFIFO,
			"receive_frame":       stats.RxFrame,
			"receive_compressed":  stats.RxCompressed,

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