/usr/share/acl2-6.3/books/rtl/rel1/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/rtl/rel1/lib1/
/usr/share/acl2-6.3/books/rtl/rel1/lib1/basic.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/bits.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/brat.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/float.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/reps.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/round.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib1/top.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/
/usr/share/acl2-6.3/books/rtl/rel1/lib3/basic.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/bits.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/brat.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/fadd.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/float.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/reps.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/round.cert
/usr/share/acl2-6.3/books/rtl/rel1/lib3/top.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/
/usr/share/acl2-6.3/books/rtl/rel1/support/add.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/away.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/basic.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/divsqrt.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/add3.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/lop1.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/lop2.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/lop3.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/stick.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fadd/top.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/float.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/floor.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/fp.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/logdefs.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/loglemmas.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/logxor-def.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/logxor-lemmas.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/merge.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/near.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/odd.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/proofs.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/reps.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/rewrite-theory.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/rnd.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/sticky.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/trunc.cert
/usr/share/acl2-6.3/books/rtl/rel1/support/x-2xx.cert