/usr/share/acl2-6.3/books/centaur/defrstobj/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/centaur/defrstobj/array-lemmas.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/basic-tests.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/def-typed-record.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/defrstobj.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/fancy-worseguy.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/g-delete-keys.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/array-rec.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/demo1.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/demo2.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/demo3.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/demo4.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/demo5.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/groundwork/local.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/portcullis.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/typed-record-tests.cert
/usr/share/acl2-6.3/books/centaur/defrstobj/typed-records.cert