Ruby on Rails Error - already activated xxxxx, but your Gemfile requires yyyyy

I am just getting started on RoR and I encounter errors like - "already activated xxxxx, but your Gemfile requires yyyyy", etc. I tried searching for info开发者_高级运维rmation to better understand the RoR gem, plug-ins loading process, but couldn't find any. Could somebody point to good resources/book which can help understand RoR mechanics.

p.s.: I am a 10+ years .Net guy making a move to RoR, interested in learning the RoR mechanics instead of just how-tos.

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Try running bundle install or bundle update... it sounds like your Gemfile has conflicting information than what your actual environment has.

If that doesn't help, use bundle exec <actual command here>.