There are more flaws than gems being missing; take a look some time and see how many different directions the ruby standard library is split.
Originally Posted by offby1
I got this hint from the Ruby on Rails website. It requires installing wajig, of course.
If I had it to do over again, I'd rather do the following (warning, not tested):
wajig install `wajig list-names ruby1.8` irb1.8 rdoc1.8 ri1.8
Then you can install Gem by hand (go on, it won't hurt.)
aptitude --with-recommends --with-suggests install `wajig list-names ruby1.8` irb1.8 rdoc1.8 ri1.8
That should be a more-or-less complete Ruby install. It was complete enough for me to install Ruby on Rails (though truth be told I'm still evaluating it and am a complete Ruby n00b.