The Rails 2 upgrade has been surprisingly painless on the half dozen or so production apps I’ve upgraded. One problem seems to be that not all the mirrors are updated, so you get “no such gem” and have to repeat the command a few times until it finds a mirror that has it. But the other one is that for some reason, the Rails 2.0.1 package doesn’t find the newly-added activeresource dependency. So the full upgrade becomes:
gem update --no-rdoc --no-ri -y update
gem install --no-rdoc --no-ri -y activeresource
Note 1: I like to skip rdoc and ri since they take a lot of time to generate, and I never find myself using local docs. Especially on a server, which is where most of my upgrades were being executed.
Note 2: You can thankfully skip the -y option now if you’re using the latest RubyGems, 0.9.5.
The activeresource dependency problem seems to happen everywhere - my Macbook, my Ubuntu workstation, and a handful of Debian (etch) servers I’ve updated. I’m surprised no one else has mentioned it.