Root partition and usrland on one slice, /usr/local ports and src on another

[lankfordandrew at charter.net]

When I installed FreeBSD 10 on an old laptop, I wanted to merge both
the root partition heirarchy (kernel /bin /sbin etc) and the rest of
Fbsd usr-land together onto one slice. I like upgrading from source,
but I do that more frequently with ports than the OS-proper. When I
need to boot up single user, it seems rather quaint these days (at
least for a laptop user) to have to mount /usr in order to get
reasonably the functionality from applications that use shared
libraries (vi, man pages, etc). The likelyhood that I'm going to fall
back on a serial port and an ASR-33 tty are nil.

So what I'd like to do is put the entire freebsd system on one fairly
small, pristine slice, but put the more bloated and ephemeral src,
ports, /usr/local, /home portions on one big slice. I tried symlinks
between "/src" or "/usr/src" and "/usr/ports" and tweaking some build
variables, but it seemed like something always breaks in some bizarre
way whenever I tried to rebuild world. I guess a lot of the strange
behavior showed up in /src/contrib and the gnu licensed side of the
build system. Can anyone suggest some docs on /src and ports,
specifically for what I'm trying to do besides "man src"?

Andrew Lankford