Is it normal to need to do a mount -u / each time I boot into MacBSD?
  (to make the fs writable)

Sounds like you are booting single user.  Do this only the first time.
  
  I tried to use vipw to make an account and  password for myself, and
  the TERM was not set. I set it to vt100, and then realized I could
  find no termcap. Where can i get one for vt100? Will any one do? Or am
  I forgetting something else to get vi to work?

The termcap file is no longer in /etc, it is somewhere down in /usr/share.
  
  What is the root password (until I get vipw to work?)

Don't know, but it is trivial to edit this file--if nothing else, you
can use the installer to read it out, edit on mac side, and write it back
in--but install the termcap, and you can use vi.  Actually, I used cat
to create a new master.passwd file...

Sam


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