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- Date: Sun, 2 Feb 86 23:48:32 pst
- >From: ihnp4!decwrl!mips!mash (John Mashey)
-
- 1] I don't believe the idea of associating uname values to directories
- was ever discussed, as far as I can remember. The whole thing really
- came about because PWB/USG believed that security had to be tightened,
- and Research and some others wanted to continue to run conveniennt loose
- systems. It was believed that setting a default per systems was fine,
- but needed to be overridden as needed, so it it was put in to be inherited
- in the same way as most other thigns, i.e., by process tree inheritance.
-
- 2] I doubt whether the idea would have been considered seriously if
- it had been brought up, at least if umask were the only reason for
- adding the mechanism. Why?
- a) Remember that UNIX was designed by people who'd been working on
- MULTICS, whose directories include considerable more protection
- information.
- b) However, UNIX directories are ONLY names. There is no
- system-implied state (except for the current directory itself)
- implied by the current directory. Nothing else is inherited or
- modified by one's position in the file system.
- c) I can't remember the reference, but I'd swear that one of the
- early papers said that b) was on-purpose.
- d) This doesn't mean the idea is necesarily bad, merely that I doubt
- anybody would have believed that it fit with UNIX.
-
- 3] [PHILOSOPHICAL HARANGUE]: kernel mechanisms should be added only
- when really justified by serious need. In particular, one should
- try to make new mechanisms be general enough to cover numerous
- special cases, not add special cases one by one. In this case,
- good questions to ask are:
- Is there per-process state information [either in the u-area
- or returned by doing a chdir(2)] that should be changed
- automatically when doing a chdir? If so, can one store this
- in a file in the directory? Are pieces of state added, deleted,
- merged, inherited, etc?
- If one can come up with a few examples, then perhaps the general
- mechanism could be designed. One could easily experiment with
- this: for example, the chdir function call might be augmented
- in any of many ways. It would be much more enlightening to hear
- a proposal for a general mechanism, backed up by multiple examples &
- illustrations of existing attempts within the systems to achieve the
- effects. [END PHILOSOPHICAL HARANGUE]
-
- [ Now *that* was an article! But I don't understand what chdir
- has to do with it: the idea is to create a new file according to
- the umask of its parent directory, not of the current directory.
- I.e., "cat this > there/that" should create "that" in the same
- modes according to the umask of "there" regardless of what "." is.
- -mod ]
-
- Volume-Number: Volume 5, Number 37
-
-