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Message-ID: <00d001c427a4$c51e3eb0$66fda287@docbill002>
From: "Bill C. Riemers" <cygwin AT docbill DOT net>
To: "Bill C. Riemers" <cygwin AT docbill DOT net>, <dmccunney AT nyc DOT rr DOT com>,
   <cygwin AT cygwin DOT com>
References: <000e01c4274e$2fcca690$73aa4142 AT arda> <009a01c427a2$ed1184b0$66fda287 AT docbill002>
Subject: Re: Emulating hard links on FAT et al.
Date: Wed, 21 Apr 2004 09:30:03 -0400
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Ack.  I do wish Outlook Express had grammar checking abilities, or I would
at least remember to proof read after correcting the spelling...

                                   Bill


----- Original Message ----- 
From: "Bill C. Riemers" <cygwin AT docbill DOT net>
To: <dmccunney AT nyc DOT rr DOT com>; <cygwin AT cygwin DOT com>
Sent: Wednesday, April 21, 2004 9:16 AM
Subject: Re: Emulating hard links on FAT et al.


> You can't expect me to just admit I was completely wrong... :)  It turns
out
> the only version of Unix I can remember that allowed separate permissions
> for hard linked files was Apollo DomainOS.  In DomainOS, separate hidden
ACL
> files where used to override and extend permissions.  Because the ACL's
were
> stored in a separate file, the net result is each hardlink could and often
> did have different permissions.   The Apollo DomainOS were truly fantastic
> machines, at least ten years ahead of their times in terms of usability
> features.  For example, it is the only version of Unix I know of that
> allowed SYSV or BSD syntax to be selected at runtime.  Unfortunately, the
> hardware itself was expensive to maintain.  The maintained contracts where
> $20,000 per year per node.  So if you wonder the halls at CERN you might
> still find one of the old Apollo machines, but chances are it is being
used
> as a coffee table or such.
>
> The cause of my original error is I vaguely remember using the separate
> permissions trick on TitanOS to avoid problems if the owner decided to
> restrict a directory later.  However, I later remembered it wasn't
separate
> permissions on the file, but separate permissions on the file path that I
> would take advantage of.
>
> i.e.  I would do something like:
>    mkdir ~/cool-program
>    ln cool-program/* ~/cool-program/.
>
> So later if the owner did something like:
>    chmod go-rwx cool-program
> -or-
>    rm -rf cool-program
>
> I would still be able to run the program without using up part of my disk
> quota with a copy.
>
> At the time I wrote my original post all I remembered was I used separate
> permissions for hard-links to cheat quotas.  I didn't remember that it was
> the separate permissions on the path, not the file, that I used.
>
>                                       Bill
>
>
> ----- Original Message ----- 
> From: "Dennis McCunney" <dmccunney AT nyc DOT rr DOT com>
> To: "'Bill C. Riemers'" <docbill AT freeshell DOT org>
> Sent: Tuesday, April 20, 2004 11:10 PM
> Subject: RE: Emulating hard links on FAT et al.
>
>
> > > -----Original Message-----
> > > From: cygwin-owner AT cygwin DOT com
> > > [mailto:cygwin-owner AT cygwin DOT com]On Behalf
> > > Of Bill C. Riemers
> > > Sent: Tuesday, April 20, 2004 5:37 PM
> > > To: cygwin AT cygwin DOT com
> > > Subject: Re: Emulating hard links on FAT et al.
> > >
> > > I stand corrected.  Only some flavors of Unix allow hardlinks to carry
> > > separate permissions.  I imagine the list of UNIX platforms which
> support
> > > this *feature* have greatly reduced in recent years since this trick
was
> > > commonly used to cheat quota systems.
> >
> > Er, what versions did this?  I've dealt at one time or another with AT&T
> > Systen V Release 2, 3, and 4, in ports for Intel, Motorola, and WE32000
> > CPUs, SunOS on SPARC, IBM's AIX on RS/6000, Red Hat and Suse Linux on
> Intel,
> > and Solaris 7, 8, and 9.
> >
> > None of them allowed seperate permissions on different hard links to a
> file.
> >
> > Given the way hard links are implemented (and Corrina has it exactly
> right),
> > I don't believe it's *possible*.  A link is simply a pointer to an
inode,
> > where the actual permissions are stored, and links to the same inode
> *must*
> > carry the same permissions.
> >
> > I suppose someone could hack a *nix kernel to store seperate permissions
> > entries for each hard link to an executable, but I've never heard of it
> > being done.
> >
> > Pointers, please?
> > ______
> > Dennis
> >
>
>
>
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