Don't know how to build task 'db:migrate' w/ Rails 3.2.0.rc2

Question

I\'m attempting to upgrade my Rails application to 3.2.0.rc2 but When I try to do a rake db:migrate --trace I\'m now getting the following error message:

Answer 1

There is something very funky going on with your gem versions. If you look at your gemfile.lock it's using the 3.2.rc2 versions of railties, activesupport and activemodel but the other versions are all over the place ( ar is 1.6, action mailer is 0.6.1 etc).

I'm not sure how you got into this state, but I'd try either bundle update or deleting Gemfile.lock and then running bundle install (in theory those 2 are equivalent) and specifying the precise version of rails you want (especially as you're after a prerelease version of rails.)