When PDC is us (the computer we are working on), it is not running at the moment we are prompted to join the domain, because 21.5.3 says "Kill off all ambd, nmbd, and winbindd processes [...]". This situation arises in case we are running winbindd because according to page xxxii 2.2.2 "winbindd [...] is [...] needed when Samba has trust relationships with another Domain".
Suggested fix: place the following text before "root# /usr/local/samba/bin/net rpc join -S PDC -U Administrator": "If the PDC is the same machine you are carrying these things out on, then start the samba daemons temporarily before the following net rpc join command and after completing this command, stop them again."
updating qa contact
The documentation has been updated. The chapter on winbind is now chapter 22.
Section 18.104.22.168 has been ammended.
sorry for the same, cleaning up the database to prevent unecessary reopens of bugs.