prometheus/node_exporter · error

failed to open procfs

Error message

failed to open procfs: %w

What it means

NewNfsCollector initializes the NFS collector by opening the procfs filesystem via nfs.NewFS(*procPath), which validates that the path is a mounted procfs. If the path cannot be opened as procfs, the constructor returns this wrapped error and the NFS collector is not registered.

Solutions

1. Ensure /proc is mounted and the --path.procfs flag points to the correct procfs root (default /proc).
2. In containers, bind-mount /proc read-only (e.g. -v /proc:/host/proc:ro with --path.procfs=/host/proc).
3. Check read permissions for the exporter user on the procfs path.
4. If NFS stats aren't needed, disable the collector instead of fixing the path.

Example fix

// before
fs, err := nfs.NewFS(*procPath)
if err != nil {
	return nil, fmt.Errorf("failed to open procfs: %w", err)
}
// after (include the configured path in the error)
fs, err := nfs.NewFS(*procPath)
if err != nil {
	return nil, fmt.Errorf("failed to open procfs at %q (check --path.procfs): %w", *procPath, err)
}

import "os"
// Check the procfs root before constructing the collector:
if st, err := os.Stat(*procPath); err != nil || !st.IsDir() {
	// fail fast: bad --path.procfs value
}

null

// Constructor-time fail-fast with context
if _, err := NewNfsCollector(logger); err != nil {
	logger.Error("NFS collector init failed; check --path.procfs", "err", err)
	os.Exit(1)
}

When it happens

Trigger: Calling NewNfsCollector when --path.procfs points to a nonexistent, unreadable, or non-procfs directory, so nfs.NewFS fails its mount validation.

Common situations: Wrong --path.procfs flag value; running in containers without /proc mounted at the expected location; running node_exporter on hosts where NFS-related procfs files are absent.

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 procfs
• failed to open procfs
• failed to open /proc/self
• failed to retrieve nfs stats
• failed to open sysfs

AI-assisted analysis of prometheus/node_exporter@17ddd77c59 (2026-09-07). Data as JSON: /api/errors/261656bd681d8645. Report an issue: GitHub.

Appendix: source

Thrown at collector/nfs_linux.go:52

	fs                                nfs.FS
	nfsNetReadsDesc                   *prometheus.Desc
	nfsNetConnectionsDesc             *prometheus.Desc
	nfsRPCOperationsDesc              *prometheus.Desc
	nfsRPCRetransmissionsDesc         *prometheus.Desc
	nfsRPCAuthenticationRefreshesDesc *prometheus.Desc
	nfsProceduresDesc                 *prometheus.Desc
	logger                            *slog.Logger
}

func init() {
	registerCollector("nfs", defaultEnabled, NewNfsCollector)
}

// NewNfsCollector returns a new Collector exposing NFS statistics.
func NewNfsCollector(logger *slog.Logger) (Collector, error) {
	fs, err := nfs.NewFS(*procPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open procfs: %w", err)
	}

	return &nfsCollector{
		fs: fs,
		nfsNetReadsDesc: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, nfsSubsystem, "packets_total"),
			"Total NFSd network packets (sent+received) by protocol type.",
			[]string{"protocol"},
			nil,
		),
		nfsNetConnectionsDesc: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, nfsSubsystem, "connections_total"),
			"Total number of NFSd TCP connections.",
			nil,
			nil,
		),
		nfsRPCOperationsDesc: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, nfsSubsystem, "rpcs_total"),

View on GitHub (pinned to 17ddd77c59)