From mboxrd@z Thu Jan 1 00:00:00 1970 From: mascheck@in-ulm.de (Sven Mascheck) Date: Fri, 29 Jul 2016 01:16:39 +0200 Subject: [TUHS] environments/universes (was: Unix v6 problem with /tmp) In-Reply-To: References: <57991A21.5030404@gmail.com> Message-ID: <20160728231639.GA299581@lisa.in-ulm.de> 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 (s.a. http://www.in-ulm.de/~mascheck/various/universes/) 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. -Sven