How to search several directories for duplicate files?

I wish to search several directories for duplicate files. This could
involve several thousands of files.

I'm not sure how to best do this in Linux rather than Windows. I Googled
and found a (very) little information on a program(?) called 'samefile',
available as an rpm, and a script 'dupfiles'. I haven't tried 'samefile'
as yet, but 'dupfiles' seems to work OK, at least on a small number of
files.

It works by first finding identical sized files and then running md5sum on
those of the same filesize. I have no idea how 'samefile' works.

Does anyone have any experience with these or other utilities or scripts?
Any thoughts on the likelihood of errors using size and md5sum vs cmp or
something similar? Any info or advice on time required with large files
or large numbers of files? Is a script too slow for something like this?

Sorry, so many questions. Maybe I should make this easier: if you wanted
to do this, what would you use and why?

I'm using PCLinuxOS, not much of a command line jockey; hardware: AMD
Sempron 1.8 GHz, 1 GB RAM, 80 GB IDE and 250 GB SATA drives.

TIA for any help :-)

Andy

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