Internal crossreferences in the FreeBSD handbook using `crossref:` are currently broken on PDF output. The official docs [0] say to use <<here-is-the-xref>>. Most links are already written with that notation, they are clean and they work great. Update the rest of the remaining xrefs in this chapter to this notation.
[0] : https://docs.asciidoctor.org/asciidoc/latest/macros/xref/
Related bug : [https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=266107]
Similar fix for audit : https://reviews.freebsd.org/D46261
Similar fix for advanced networking : [https://reviews.freebsd.org/D46258]
Similar fix for basics : [https://reviews.freebsd.org/D46260]