Re: ln and -F

[Chris Humphries <chumphries@drauku.net>]

yes it is helpful, i think i understand ffs and fsck, and inodes work
_alot_ better than 24 hours ago. this -s + -F thread i shouldnt have
even started cause the source wont allow it, and after the emails and
docs i have started reading/am reading, shows that it just doesnt make
sense (like /usr/share/doc/smm/03.fsck_ffs, thanks another Chris).

thanks for the bonks on the head with the cluestick bat, from those that
knew what they were talking about :) Sorry for the ignorant posts,
think i learned my lesson good this time :)

-chris

Zvezdan Petkovic writes:
 > On Sun, Jul 21, 2002 at 01:08:09AM -0500, Chris Humphries wrote:
 > > yes, i have just been doing some reading on that, and one should still
 > > be able to use -F for symlinks, correct? so why not enable a logic
 > > rule that makes it where you have to have -s in conjunction with it,
 > > or else it will not work?
 > > 
 > 
 > Not correct.
 > 
 > -s works for both files _and_ directories _without_ anything else.
 > Symbolic links create a new inode in the filesystem and put in its data
 > blocks a path to the inode which they are linking to. They do _not_
 > touch the original inode. Hence, it doesn't matter what is the type of
 > the original inode.
 > 
 > The filesystem lookup() will resolve a symlink by simply continuing
 > the search for the path it contains in its data block. When it finally
 > reaches its destination it will recognize from the target inode whether
 > it is a file or a directory.
 > 
 > Hard links however do _not_ create a new inode. They change the
 > _original_ inode by changing the corresponding link count in the inode
 > structure. 
 > 
 > Both types of links write an entry in a directory they are linking from
 > which makes the correspondence between an inode and its name. However,
 > if you do
 > 	ls -li
 > in a directory containing both types of links to the same file you will
 > see that hard link has the same inode number as the original inode and
 > link count (the number next to permission bits rw-r--r--) is 2 or
 > larger, while the symbolic link has totally different inode number and
 > link count 1 -- because it's a different inode and nobody else links to
 > it!
 > 
 > Also the size of a hard link file is the same as the size of the
 > original file, while the size of a symlink file is the length of the
 > string containing the path to the original file.
 > 
 > Hard link to a directory would create a loop in the filesystem graph and
 > that would really confuse the programs relying on the graph traversal
 > (e.g. fsck).
 > 
 > > I just think that if something is supported, it should be documented
 > > if, binding it to -s will make it useful and safe? If one wants to
 > > hardlink to a directory then have them hack the code to get it to
 > > work, but if it is safe to soft link to a directory, why not enable it
 > > and bind -F to -s as a logic rule?
 > > 
 > 
 > I hope the above explanation helps you understand that -s already works
 > just fine and there are good reasons not to advertise -F.
 > 
 > > of course, i am not an expert on all the gnomes that can come to life
 > > on this.  i am still reading. your thoughts?
 > > 
 > > -chris
 > > 
 > 
 > I see.
 > 
 > Best regards,
 > -- 
 > Zvezdan Petkovic <zvezdan@cs.wm.edu>
 > http://www.cs.wm.edu/~zvezdan/