rsync - Oct 2002 - Exclude symbolic link to a directory?

Hi folks,

	I have a subtle problem with rsync that I'm hoping has a simple
answer.  I have a directory tree (call it /local) that I synchronize
every night onto a group of about 100 machines.  This works great.
On a few of these machines, one of the subdirectories of /local
(call it /local/stuff) needs to be a symbolic link to a directory
on another device.  So, the situation looks like this:

Most machines:			A few machines:

/local				/local
    |-- stuff			    |-- stuff -> /elsewhere/stuff
           |-- things		    |
    |-- morestuff		    |-- morestuff
    `-- stillmorestuff		    `-- stillmorestuff

(obviously the trees are much larger than this, but you get the idea.)

	The master copy of /local contains the directory "stuff", not
a symbolic link.  The problem is, when I rsync /local on the few
machines that have a symbolic link, the link gets nuked and replaced
with a real directory (just like in the master copy).

	The script that does the rsync looks for a local include/exclude
list, so what I'd like to do is just tell rsync to exclude
"stuff".
Unfortunately, I don't want to exclude the "things" that live
under stuff.

	What I've tried is excluding "/local/stuff" and including 
"/local/stuff/*", but the stuff symlink still gets nuked.

	Is there any easy way to do what I want with rsync, without
having to re-write my rsync script?

					Thanks in advance,
					Bryan
-- 
==============================================================================Bryan
Wright                |"If you take cranberries and stew them like
Physics Department          | applesauce, they taste much more like prunes 
University of Virginia      | than rhubarb does."  --  Groucho 
Charlottesville, VA  22901  |			
(434) 924-7218              |         bryan@virginia.edu
===============================================================================

On Thu, Oct 10, 2002 at 10:49:33AM -0400, Bryan K. Wright
wrote:
> 	The master copy of /local contains the directory "stuff", not
> a symbolic link.  The problem is, when I rsync /local on the few
> machines that have a symbolic link, the link gets nuked and replaced
> with a real directory (just like in the master copy).
Correct.  That's the only thing that rsync currently knows how to do
with symlinks to directories -- make them identical with what's on the
server.  The easiest way around this at the moment is to break up the
rsync command into multiple runs, one which excludes all the potential
symlink differences, and one for each symlink dir that you want to
transfer.
> 	What I've tried is excluding "/local/stuff" and including 
> "/local/stuff/*", but the stuff symlink still gets nuked.
I don't think you were successful at getting the dir excluded, then, or
else it would have been untouched, not nuked.  Rsync would not have done
what you wanted, though, since it has to send the /local/stuff dir to
try to send what's inside it (when working recursively).  You probably
did an exclude of "/local/stuff" rather than "/stuff" (since
I assume
that the base dir is probably "/local").

So, a solution like this should work:

rsync -av --exclude="/stuff" /local/ remote:/local
rsync -av /local/stuff/ remote:/local/stuff

A better, long-term fix would be to add an option that would allow
certain symlinks to be treated as a directory.  To do this, we need to
work out a good heuristic on how to differentiate which is which.  I
imagine using the following rules (when the new option is enabled):

 - If a symlink points inside the hierarchy being transferred, treat it
   as a normal symlink to duplicate (rsync already has code to determine
   this for its "safe symlink" handling).

 - If a symlink points outside the transfer AND it points to a
   directory, treat it as if it were the actual directory for the
   transfer (I think that only the delete code would need to know that
   it wasn't a real directory).

How does that sound?  It should be fairly easy to implement.

..wayne..