What causes "error creating task %q dir: %w" in hashicorp/nomad?

Fix permissions on the target alloc dir

error creating task %q dir: %w

Error message

error creating task %q dir: %w

What it means

During Move, when the previous allocation has a task-local directory, the new task directory is created with os.MkdirAll before renaming the local dir in. If MkdirAll fails (permissions, disk full, path conflicts), Move returns 'error creating task %q dir'. The migration is aborted for safety.

Source

Thrown at client/allocdir/alloc_dir.go:308

	dataDir := filepath.Join(a.SharedDir, SharedDataDir)
	if fileInfo, err := os.Stat(otherDataDir); fileInfo != nil && err == nil {
		os.Remove(dataDir) // remove an empty data dir if it exists
		if err := os.Rename(otherDataDir, dataDir); err != nil {
			return fmt.Errorf("error moving data dir: %w", err)
		}
	}

	// Move the task directories
	for _, task := range tasks {
		otherTaskDir := filepath.Join(other.AllocDirPath(), task.Name)
		otherTaskLocal := filepath.Join(otherTaskDir, TaskLocal)

		fileInfo, err := os.Stat(otherTaskLocal)
		if fileInfo != nil && err == nil {
			// TaskDirs haven't been built yet, so create it
			newTaskDir := filepath.Join(a.AllocDir, task.Name)
			if err := os.MkdirAll(newTaskDir, fileMode777); err != nil {
				return fmt.Errorf("error creating task %q dir: %w", task.Name, err)
			}
			localDir := filepath.Join(newTaskDir, TaskLocal)
			os.Remove(localDir) // remove an empty local dir if it exists
			if err := os.Rename(otherTaskLocal, localDir); err != nil {
				return fmt.Errorf("error moving task %q local dir: %w", task.Name, err)
			}
		}
	}

	return nil
}

// Destroy tears down previously build directory structure.
func (a *AllocDir) Destroy() error {
	// Unmount all mounted shared alloc dirs.
	mErr := new(multierror.Error)
	if err := a.UnmountAll(); err != nil {
		mErr = multierror.Append(mErr, err)

View on GitHub (pinned to 482b49bf1a)

Solutions

Fix permissions on the target alloc dir
Free disk space / resolve quota pressure
Remove the conflicting non-directory path at a.AllocDir/task.Name
Retry migration after the filesystem issue is resolved

Defensive patterns

Strategy: validation

Validate before calling

if st, err := os.Stat(targetTaskDir); err == nil && !st.IsDir() {
  return fmt.Errorf("%s exists and is not a directory", targetTaskDir)
}

Try / catch

if err := allocDir.Move(other, tasks); err != nil && strings.Contains(err.Error(), "error creating task") {
  // check disk space and permissions on alloc dir before retrying
}

Prevention

Monitor node disk space/quota before mass migrations
Clean stale alloc dirs to avoid name collisions
Keep alloc dir permissions consistent across node re-provisioning

When it happens

Trigger: os.MkdirAll(a.AllocDir/task.Name, 0777) fails — target alloc dir read-only, disk full, a file exists where the directory should be, or parent dir missing/permission-denied.

Common situations: Disk quota exhaustion on nodes with many migrations; leftover files named like task dirs from corrupted prior runs; permissions changed by external tooling; read-only mounts after node incidents.

Understand the failure class

Background: mkdir permission denied (EACCES): failed to create directory errors explained — this error's family across 32 libraries.

Related errors

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/5096390a8c55b0db. Report an issue: GitHub.