rails server doesn't start

/home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/core_ext/object/json.rb:2:in `require': cannot load such file -- json (LoadError)   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/core_ext/object/json.rb:2:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/core_ext/object.rb:11:in `require'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/core_ext/object.rb:11:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/configuration.rb:2:in `require'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/configuration.rb:2:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/railtie/configuration.rb:1:in `require'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/railtie/configuration.rb:1:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/railtie.rb:216:in `config'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/railtie.rb:122:in `config'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/i18n_railtie.rb:7:in `<class:Railtie>'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/i18n_railtie.rb:6:in `<module:I18n>'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/i18n_railtie.rb:5:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/railtie.rb:2:in `require'   from /home/impulsief/.gem/ruby/gems/activesupport-5.0.0/lib/active_support/railtie.rb:2:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails.rb:14:in `require'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails.rb:14:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/server.rb:4:in `require'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/server.rb:4:in `<top (required)>'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/commands_tasks.rb:138:in `require'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/commands_tasks.rb:138:in `require_command!'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/commands_tasks.rb:83:in `server'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands/commands_tasks.rb:49:in `run_command!'   from /home/impulsief/.gem/ruby/gems/railties-5.0.0/lib/rails/commands.rb:18:in `<top (required)>'   from bin/rails:4:in `require'   from bin/rails:4:in `<main>'

rails -v 5.0.0

ruby -v ruby 2.2.5p319 (2016-04-26 revision 54774) [x86_64-linux]

gem -v 2.4.8

Have you run bundle install ?

If so then post Gemfile and Gemfile.lock

Colin