I actually did this very recently.. it was a pain in the *** really.
http://ifakedit.com/log/2006/03/28/rails-on-fedora-plesk-fiasco/
It looks like there's no RPM for RUBY 1.8.2 for FC2. Rails needs 1.8.2 at least.
You're going to have to compile ruby on your own from source.. in fact there's a ton of stuff you're going to have to compile on your own most likely.
Personally I'm somewhat new to linux and I hadn't really been comfortable with doing any of the stuff i did to make this work.. if you want it to work though you're going to have to get comfortable with it.
Anyway.. most everything i did is in the notes in that url. The summary is:
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I did it on Fedora Core 2 with Plesk 7.5 and Apache2
If you're on Apache 2 don't bother getting fcgi to work.
Even if you DO get it to work you probably won't want to use it because there are some serious problems with apache2+fcgi
DO use fcgid
If something won't compile it's probably because you don't have the required libraries or something from the package. You may THINK you have sometihng installed, but you most likely don't have all the pieces of it. To remedy this situation you'll need to install packagename-devel rpms.. most favorably through yum.
DO use the
rails wiki. Look around not only at plesk stuff, but just general installation instructions.. especially for your linux distro.
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i wish i had more to say, but it's already been said in that log entry. hope this helps some of you out.