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Message-ID:	<003601c42720$42f7f680$66fda287@docbill002>
From:	"Bill C. Riemers" <cygwin AT docbill DOT net>
To:	<cygwin AT cygwin DOT com>
References:	<F76C9B2DA2FC4C4CA0A18E288BBCBCF7082177FA AT nihexchange24 DOT nih DOT gov> <00da01c42709$d9daca80$66fda287 AT docbill002> <20040420203516 DOT GB31665 AT cygbert DOT vinschen DOT de>
Subject:	Re: Emulating hard links on FAT et al.
Date:	Tue, 20 Apr 2004 17:40:49 -0400
MIME-Version:	1.0
X-IsSubscribed:	yes

I stand corrected.  Only some flavors of Unix allow hardlinks to carry
separate permissions.  I believe I became confused, because hardlinks
always allow separate path permissions.

i.e.

   mkdir /tmp/fi
   mkdir /tmp/bar
   touch /tmp/fi/foo.txt
   ln /tmp/fi/foo.txt /tmp/bar/foo.txt
   chmod 000 /tmp/fi
   chmod 777 /tmp/bar

Now that I think about it the last time I saw a Unix system that allowed the
actual files to have separate permissions was TitanOS.  And that was a bad
idea, since most users used this feature to cheat the disk quota system.

                                           Bill

----- Original Message ----- 
From: "Corinna Vinschen" <corinna-cygwin AT cygwin DOT com>
To: <cygwin AT cygwin DOT com>
Sent: Tuesday, April 20, 2004 4:35 PM
Subject: Re: Emulating hard links on FAT et al.


> On Apr 20 15:00, Bill C. Riemers wrote:
> > One obvious thing hard links allow is a way to have the same file with
> > different permissions.  With a symbolic link you need both access
> > permissions for the symbolic link and actual file.  i.e.
> >
> >   ln -s /tmp/foo.exe /home/bcr/foo.exe
> >   chmod ugo-x /tmp/foo.exe
> >   chmod ugo+x /home/bcr/foo.exe
> >
> > With a hardlink, you only need access permissions for the hardlink...
>
> That's not how it works.  Hardlinks are nothing but multiple directory
> entries for the same file.  The directory entry typically only consists
> of a name and a inode number.  The inode contains the file specific
> control information.  Obviously hardlinks to the same file point to
> the same inode.  Therefore all hardlinks to the same file have the same
> permissions, owner, etc, since it's *one* file with *one* owner and *one*
> set of permissions.  And, yes, it's implemented on NTFS like this.
>
>
> Corinna
>
> -- 
> Corinna Vinschen                  Please, send mails regarding Cygwin to
> Cygwin Co-Project Leader          mailto:cygwin AT cygwin DOT com
> Red Hat, Inc.
>
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