Subject: Re: link(1) - when did it disappear?
To: None <>
From: Bill Studenmund <>
List: tech-userlevel
Date: 07/19/1999 14:11:46
On Sun, 18 Jul 1999, Lucio De Re wrote:

> On Sun, Jul 18, 1999 at 06:50:38PM +1000, Giles Lean wrote:
> > 
> > 
> > Historically on BSD systems ln(1) would do this if the user was
> > superuser.  Not all filesystems now support links to directories.
> > This behaviour is more or less deprecated.

And it's REALLY dangerous. While the setup you describe (multiple
directory entries sitting in the same directory point to the same dir) 
isn't super evil, the ability to give a directory multiple parrents
(directories which contain an entry pointing to it) is nasty. As Christos
said, you can get into a position of making many tools get into infinite
loops, and to make fsck unusable. Also, you could mess up the vnode
locking & get into deadlocks as the lookup protocol assumes the directory
tree is a tree. :-)

> Well, I think one of NetBSD's good points is its liberal approach: "Give
> them enough rope..." type thing.  This is a piece of rope I really want
> quite badly.

The problem here is that this rope can not only hang the admin, but also
the kernel. If you get a vnode locking deadlock, you sieze the machine
hard. :-)

Take care,