prometheus/node_exporter · error

failed to open procfs

Error message

failed to open procfs: %w

What it means

NewNetStatCollector initializes the Linux netstat collector by opening the procfs filesystem at the path given by the --path.procfs flag via procfs.NewFS. If procfs cannot be opened/mounted at that path, the collector constructor fails with this wrapped error and the collector is not registered.

Solutions

1. Ensure /proc exists and is a mounted procfs filesystem (mount | grep proc).
2. Check the --path.procfs flag points at the correct procfs root (default /proc).
3. In containers, mount /proc into the container (e.g. docker run -v /proc:/host/proc:ro and --path.procfs=/host/proc).
4. Verify filesystem permissions allow the node_exporter user to read the procfs path.

Example fix

// before
fs, err := procfs.NewFS(*procPath)
if err != nil {
	return nil, fmt.Errorf("failed to open procfs: %w", err)
}
// after (fail fast with an actionable hint)
fs, err := procfs.NewFS(*procPath)
if err != nil {
	return nil, fmt.Errorf("failed to open procfs at %q (is it mounted? is --path.procfs correct?): %w", *procPath, err)
}

import "os"
// Call before starting the collector:
if st, err := os.Stat(*procPath); err != nil || !st.IsDir() {
	// fail fast: procfs path missing or not a directory
}

null

// Wrap collector construction and fail startup with context
if _, err := NewNetStatCollector(logger); err != nil {
	logger.Error("netstat collector init failed", "err", err)
	os.Exit(1)
}

When it happens

Trigger: Calling NewNetStatCollector when *procPath points to a directory that does not exist, is not readable, or is not a procfs filesystem (procfs.NewFS validates the mount).

Common situations: Running node_exporter in a container without /proc mounted or mounted elsewhere; passing a wrong --path.procfs value; running on a non-Linux host or a restricted environment where /proc access is blocked.

Understand the failure class

Background: "open() failed", "failed to open file", "cannot create file" — what a file open error means and how to fix it — this error's family across 42 libraries.

Related errors

• failed to open /proc/self
• couldn't get netstats
• failed to open procfs
• failed to open sysfs
• interrupts empty

AI-assisted analysis of prometheus/node_exporter@17ddd77c59 (2026-09-07). Data as JSON: /api/errors/e3c6d46094e84760. Report an issue: GitHub.

Appendix: source

Thrown at collector/netstat_linux.go:61

)

type netStatCollector struct {
	proc         procfs.Proc
	fieldPattern *regexp.Regexp
	logger       *slog.Logger
}

func init() {
	registerCollector("netstat", defaultEnabled, NewNetStatCollector)
}

// NewNetStatCollector takes and returns
// a new Collector exposing network stats.
func NewNetStatCollector(logger *slog.Logger) (Collector, error) {
	pattern := regexp.MustCompile(*netStatFields)
	fs, err := procfs.NewFS(*procPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open procfs: %w", err)
	}

	// Network statistics in /proc/net are network namespace local. Reading
	// them via the current process' /proc/self/net keeps the same semantics
	// while allowing the use of the procfs parsers.
	proc, err := fs.Self()
	if err != nil {
		return nil, fmt.Errorf("failed to open /proc/self: %w", err)
	}

	return &netStatCollector{
		proc:         proc,
		fieldPattern: pattern,
		logger:       logger,
	}, nil
}

func (c *netStatCollector) Update(ch chan<- prometheus.Metric) error {

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