hashicorp/nomad · error

error creating fifo: %w

Error message

error creating fifo: %w

What it means

The final step of the mkfifoat-based creation calls unix.Mkfifoat with the parent directory's FD to create the FIFO relative to that directory. This error wraps any Mkfifoat failure: EEXIST (FIFO already there), ENOENT/EACCES on the base name, ENAMETOOLONG, or unsupported filesystem.

Source

Thrown at client/lib/fifo/mkfifoat.go:36

	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. Ignore os.ErrExist if concurrent creation is expected: errors.Is(err, os.ErrExist)
2. Remove stale FIFOs with fifo.Remove before creating
3. Shorten the FIFO path/name if ENAMETOOLONG
4. Create FIFOs on a local filesystem that supports them (tmpfs/local disk), not unsupported network FS

Example fix

// before
if err := fifo.Create(path, 0o600); err != nil { return err }
// after
if err := fifo.Create(path, 0o600); err != nil && !errors.Is(err, os.ErrExist) { return err }

if len(filepath.Base(path)) > 255 {
	return fmt.Errorf("fifo base name too long")
}
if _, err := os.Stat(path); err == nil {
	return fmt.Errorf("fifo %s already exists", path)
}

err := fifo.Create(path, mode)
if err != nil && !errors.Is(err, os.ErrExist) {
	return fmt.Errorf("create fifo %s: %w", path, err)
}

When it happens

Trigger: Calling fifo.Create(path, mode) when the FIFO already exists at path, the base name is too long or invalid, permissions deny creation, or the filesystem (e.g. some network/overlay FS) does not support FIFOs.

Common situations: Double-creation of a FIFO during concurrent IO setup; FIFOs left over from a prior container run; extremely long pipe names exceeding NAME_MAX; creating FIFOs on filesystems like certain NFS mounts that disallow special files.

Related errors

• error creating fifo: %w
• error opening fifo parent directory %q: %v
• error getting file handle to fifo parent directory %q: %v
• error creating fifo %v: %w
• error opening fifo parent directory %q: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/378280bdf026c906. Report an issue: GitHub.