On Debian 5 (Lenny) after installing ImageMagick and rmagick, when testing my rails application:
libMagickCore.so.2: cannot open shared object file: No such file or directory – /usr/lib/ruby/gems/1.8/gems/rmagick-2.8.0/lib/RMagick2.so
Missing these required gems: rmagick ...

At first I thought it must be a problem of rmagick because apaches module passenger raises up an error about missing rmagick…

But if you look closer into the problem, youll see that the libraries of Imagemagick arent found in that folders where they are excepted to be.

So what can you can do now?

1. The easiest way is to type this into the console, so the libs are getting found: ldconfig /usr/local/lib
2. compile Imagemagic again with explicitly setting the libpath to /usr/lib where the libraries are excepted.