hashicorp/nomad · error

error chmoding file %w

Error message

error chmoding file %w

What it means

While streaming the previous allocation's directory as a tar archive in streamAllocDir, f.Chmod on a newly created regular file failed, aborting the migration of the alloc dir to the new node. The file is closed before returning so no descriptor leaks.

Source

Thrown at client/allocwatcher/alloc_watcher.go:659

			continue
		}
		// If the header is a file, we write to a file
		if hdr.Typeflag == tar.TypeReg {
			fPath := filepath.Join(dest, hdr.Name)
			if _, err := os.Lstat(fPath); err == nil {
				if err := os.Remove(fPath); err != nil {
					return fmt.Errorf("error removing existing file: %w", err)
				}
			}
			f, err := os.Create(fPath)
			if err != nil {
				return fmt.Errorf("error creating file: %w", err)
			}

			// Setting the permissions of the file as the origin.
			if err := f.Chmod(os.FileMode(hdr.Mode)); err != nil {
				f.Close()
				return fmt.Errorf("error chmoding file %w", err)
			}

			// Can't change owner if not root or on Windows.
			if euid == 0 {
				if err := f.Chown(hdr.Uid, hdr.Gid); err != nil {
					f.Close()
					return fmt.Errorf("error chowning file %w", err)
				}
			}

			// We write in chunks so that we can test if the client
			// is still alive
			for !canceled() {
				n, err := tr.Read(buf)
				if n > 0 && (err == nil || err == io.EOF) {
					if _, err := f.Write(buf[:n]); err != nil {
						f.Close()
						return fmt.Errorf("error writing to file %q: %w", f.Name(), err)

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Move the Nomad data dir onto a POSIX filesystem (ext4/xfs) instead of FAT/NTFS/network mounts
2. Check SELinux/AppArmor audit logs and add allow rules for the Nomad client
3. Inspect the archive header Mode values for unsupported bits
4. Retry the migration after fixing the destination filesystem

// Verify the destination filesystem supports chmod before placing the data dir:
// f, _ := os.Create(probe); err := f.Chmod(0644); if err != nil { filesystem unsupported }

if err := watcher.Wait(ctx); err != nil {
    if strings.Contains(err.Error(), "error chmoding file") {
        // fall back to a fresh alloc without migrating preserved permissions
        return startWithoutMigration(ctx, alloc)
    }
    return err
}

When it happens

Trigger: os.Create succeeds but f.Chmod(hdr.Mode) returns an error during TypeReg extraction — e.g. read-only or special filesystems rejecting attribute changes, or fd issues.

Common situations: Files created on FAT/NTFS or other filesystems with limited permission support; security modules (SELinux/AppArmor) blocking chmod; unusual mode bits in a hand-crafted archive (e.g. setuid on restricted FS).

Related errors

• Chmod(%v) failed: %w
• plugin not executable
• Couldn't change owner/group of %v to (uid: %v, gid: %v): %w
• unable to remove existing unix socket: %w
• failed to write vault token to secrets dir: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/cbeb89e14cbcddab. Report an issue: GitHub.