"rails s" doesn't work but "bundle exec rails s" works. Why?

I copied the app from Github. Installed a proper version of Ruby using rbenv. I installed bundler by gem install bundler and ran bundle install --path vendor/bundle. All gems were installed in vendor/bundle directory in the app. Now I wonder, why rails s command doesn't work but bundle exec rails s works? The same with rspec command. Is this because I installed gems in vendor/bundle directory? I'm confused.

Also, when I run gem list I get only a few gems, but there are a lot of them in vendor/bundle directory.

Please tell me why gem list command doesn't see gems from vendor/bundle directory and why I need to run commands with bundle exec. Thank you!


  • The purpose of having the bundle exec command is to look/search for the command which you want to run inside the current bundle or installed gems inside your vendor directory.

    If you are running newer rails (v5) then have a look at the binstubs which copies over the command executeable in the bin directory. So that you can simply call

    bin/rails server

    This is the same approach which is followed by the deployment solutions which we currently have. They create a .bundle directory which eliminates the need to do bundle install everytime.