grpck: unrecognized option '--invalid'
Usage: grpck [options] [group [gshadow]]

Options:
  -h, --help                    display this help message and exit
  -r, --read-only               display errors and warnings
                                but do not change files
  -R, --root CHROOT_DIR         directory to chroot into
  -s, --sort                    sort entries by UID