hashicorp/nomad · error

Failed to make the alloc directory %v: %w

Error message

Failed to make the alloc directory %v: %w

What it means

AllocDir.Build() creates the allocation directory tree; it starts with os.MkdirAll on a.AllocDir with mode 0755. If directory creation fails, the error is wrapped in this message identifying the directory path.

Source

Thrown at client/allocdir/alloc_dir.go:359

func (a *AllocDir) UnmountAll() error {
	a.mu.RLock()
	defer a.mu.RUnlock()

	mErr := new(multierror.Error)
	for _, dir := range a.TaskDirs {
		if err := dir.Unmount(); err != nil {
			mErr = multierror.Append(mErr, err)
		}
	}

	return mErr.ErrorOrNil()
}

// Build the directory tree for an allocation.
func (a *AllocDir) Build() error {
	// Make the alloc directory, owned by the nomad process.
	if err := os.MkdirAll(a.AllocDir, fileMode755); err != nil {
		return fmt.Errorf("Failed to make the alloc directory %v: %w", a.AllocDir, err)
	}

	// Make the shared directory and make it available to all user/groups.
	if err := allocMkdirAll(a.SharedDir, fileMode755); err != nil {
		return err
	}

	// Create shared subdirs
	for _, dir := range SharedAllocDirs {
		p := filepath.Join(a.SharedDir, dir)
		if err := allocMkdirAll(p, fileMode777); err != nil {
			return err
		}
	}

	// Mark as built
	a.mu.Lock()
	a.built = true

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Fix os.MkdirAll error cause: check permissions on the alloc dir path and its parents
2. Ensure the path is not occupied by a regular file; remove or move it
3. Verify the filesystem is writable and has free space
4. Correct the client data_dir/alloc_dir configuration to a writable location

Example fix

// before
client {
  data_dir = "/ro-mount/nomad"
}
// after
client {
  data_dir = "/var/lib/nomad"
}

if fi, err := os.Stat(allocDir.AllocDir); err == nil && !fi.IsDir() {
    os.Remove(allocDir.AllocDir) // clear non-directory blocking MkdirAll
}
if err := os.MkdirAll(allocDir.AllocDir, 0o755); err != nil {
    return err
}

if err := allocDir.Build(); err != nil {
    if errors.Is(err, fs.ErrPermission) || errors.Is(err, syscall.EROFS) {
        return fmt.Errorf("check data_dir writability: %w", err)
    }
    return err
}

When it happens

Trigger: Calling AllocDir.Build() when os.MkdirAll(a.AllocDir) fails: parent path does not exist and cannot be created, permission denied, read-only filesystem, or the path exists as a non-directory file.

Common situations: Misconfigured client data_dir / alloc dir on a read-only or full volume; nomad agent lacking permissions under /var; a stale regular file occupying the alloc dir path after a bad restore.

Related errors

• failed to remove alloc dir %q: %w
• Failed to lookup nobody user: %v
• Failed to create task mount directory: %v
• Failed to mount task dir: %v
• Failed to mount alloc dir: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/c0c3159b050f11c9. Report an issue: GitHub.