hashicorp/nomad · error

error getting file handle to fifo parent directory %q: %v

Error message

error getting file handle to fifo parent directory %q: %v

What it means

After opening the parent directory with os.Root, this mkfifo variant calls root.Open(".") to obtain a file handle to the parent directory itself, needed because os.Root does not expose mkfifoat. This error is returned when opening that handle fails, even though OpenRoot succeeded — an unexpected internal I/O failure (e.g. the directory was removed concurrently, or fd/handle limits hit).

Source

Thrown at client/lib/fifo/mkfifoat.go:28

	"os"
	"path/filepath"

	"golang.org/x/sys/unix"
)

func mkfifo(path string, mode uint32) (err error) {
	dir := filepath.Dir(path)
	base := filepath.Base(path)

	root, err := os.OpenRoot(dir)
	if err != nil {
		return fmt.Errorf("error opening fifo parent directory %q: %v", dir, err)
	}
	defer root.Close()

	parent, err := root.Open(".")
	if err != nil {
		return fmt.Errorf("error getting file handle to fifo parent directory %q: %v", dir, err)
	}
	defer parent.Close()

	// os.Root doesn't support creating a FIFO, so we need to drop to the
	// syscall and grab the parent's FD
	err = unix.Mkfifoat(int(parent.Fd()), base, mode)
	if err != nil {
		return fmt.Errorf("error creating fifo: %w", err)
	}
	return nil
}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Re-run creation; retry usually succeeds if a concurrent removal raced
2. Raise the file-descriptor limit (ulimit -n / systemd LimitNOFILE) if EMFILE/ENFILE
3. Ensure no concurrent cleanup deletes the parent directory during IO setup
4. Upgrade the library / check filesystem support if the FS cannot open directory handles

Example fix

// before
// assuming fd exhaustion
if err := fifo.Create(path, mode); err != nil { return err }
// after
if err := fifo.Create(path, mode); err != nil {
	if errors.Is(err, syscall.EMFILE) || errors.Is(err, syscall.ENFILE) {
		return fmt.Errorf("fd limit reached; raise LimitNOFILE: %w", err)
	}
	return err
}

err := fifo.Create(path, mode)
if err != nil {
	if isFdExhaustion(err) { // EMFILE/ENFILE
		// raise limit or free fds, then retry
	}
	return err
}

When it happens

Trigger: Calling fifo.Create when the parent directory is deleted between OpenRoot and root.Open("."), the handle is denied by the OS, or the process is out of file descriptors (EMFILE/ENFILE).

Common situations: Concurrent cleanup deleting the runtime dir while IO setup runs; fd leaks exhausting the descriptor limit in long-running daemons; exotic filesystems not supporting opening directories.

Related errors

• error opening fifo parent directory %q: %v
• error creating fifo: %w
• error creating fifo %v: %w
• error opening fifo parent directory %q: %w
• error opening reader at %s: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/c6596c559f3e1112. Report an issue: GitHub.