Install acl2-books-certs by entering the following commands in the terminal:
sudo apt update sudo apt install acl2-books-certs
Computational Logic for Applicative Common Lisp: library certificates
ACL2 is both a programming language in which you can model computer systems and a tool to help you prove properties of those models. . This file contains certification records for the various precompiled libraries supplied in the ACL2-books package. ACL2 essentially requires that all included books be certified before use.