[TUHS] environments/universes (was: Unix v6 problem with /tmp)
mascheck at in-ulm.de
Fri Jul 29 09:16:39 AEST 2016
On Wed, Jul 27, 2016 at 04:57:47PM -0400, Clem Cole wrote:
> I created Conditionally Dependant Symlinks (CDSL) which I think only showed
> up in Masscomp's RTU, Stellix and Tru64. The were not only late binding,
> but added the concept of a user settable context. Very handy when trying
> to create a "single system image" from multiple system.
How did you implement it?
> Also, around the same time that Dennis added symlinks, Apollo's Aegis (aka
> Domain) guys came up with a cool idea where you can run application code
> from a link - extensible types. I remember talking to Dennis and Ken
> about them at a SOSP IIRC, and toyed with putting them into one of the
> Locus UNIX Kernels. We proposed it for HP-UX and Tru64, but never got
> funded to try it, although I think / believe others did some where else.
I just wonder if and how the following are related to the above two.
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
HP-UX 9 "context dependent files" (as early alternative to NFS) make use of
the set uid bit on directories and work like this,
# mkdir /etc/inittab
# chmod +H /etc/inittab
# touch /etc/inittab+/node1 /etc/inittab+/default
By accessing /etc/inittab, node1 will see the file node1, other systems
will see default (s.a. http://www.in-ulm.de/~mascheck/various/permissions/)
> You are right the BSD 4.2 made the world know about them but like
> a number of things in BSD (such as networking) it was in some
> cases a (better) integration of ideas others had played with before.
F.i. #! also got widely known in 4.2BSD but was suggested by DMR before 8th ed.
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