[TUHS] environments/universes (was: Unix v6 problem with /tmp)

[arnold at skeeve.com]

Sven Mascheck <mascheck at in-ulm.de> wrote:

> Sequent Dynix "universes" (idea picked up by Siemens Sinix) puts several
> targets in one symlink. Example:
>
>   ln -c ucb=.bin att=/usr/att/bin   /bin
>
> and the actual resolving (and usage of different default PATHs)
> is controlled by an environment variable, as far as I know
> (s.a. http://www.in-ulm.de/~mascheck/various/universes/)

Pyramid did something similar, also called universes, in the mid-80s.
I think they used a system call and corresponding command to set
the visible universe either to BSD or System V. I don't remember the
details as to how exactly it worked.

I *think* this was before Dynix, but I'm not sure.

We had a Pyramid when I was working at Georgia Tech. DMR visited one time
and spoke; I remember him saying that he thought what Pyramid had done
was an awful idea... :-) (They were interesting machines. It was RISC,
with loadable microcode... About the same speed as a Vax 780 but half
the price.)

Arnold