[lug] rsync to explore file system differences?

[stimits at comcast.net]

I'm working with an application which creates a linux installation via a copy of an existing file system, but it then updates this dependent upon boot loader choices and installation choices. So basically there is a reference root file system, plus a derived root file system. The derived and original file systems are both available on the same computer at the same time. I wanted to do some testing to see any changes introduced by the program, along with validating that the file content has not changed.
 
Method 1 to do this would be to use something like find, ls, and sha1sum on every single file and directory, comparing between the two...this is a long and difficult way to do it.
 
For method 2 I thought about letting rsync do this instead, as it has a "--dry-run" option. This would have some advantages, such as rsync already knowing about things like file dates and checksums without actually altering anything. The problem there is that it isn't working as expected. Without verbose mode rsync doesn't really say anything. With verbose mode it seems network details like bytes sent is mainly what rsync comments on. I've also had issues with verbose mode and --dry-run ending up telling me about things I don't want to know about, e.g., empty files which are otherwise exact on both sides (and yet I have not used any options to tell it to remove or ignore empty files/directories).
 
So with manually going through every single file and directory on two essentially complete linux file systems not being particularly practical, and with rsync not providing the output I need while putting out other information I don't need, are there any other existing solutions to comparing two complete systems which are expected to match? Perhaps there are other utilities for backup and restore which could be used explore large directory tree differences?
 
Thanks,
D. Stimits, stimits AT comcast DOT net
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