Rails 无法启动加载错误答案

【问题标题】：Rails cannot be started Load ErrorRails 无法启动加载错误
【发布时间】：2015-09-29 11:28:51
【问题描述】：

我尝试重新安装我的 rails 并删除我的 .rbenv 并重新安装。这些方法都不起作用。我正在使用 Rails 4.2.1。

这是我在“rails server start”时遇到的错误：

/Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/activesupport-4.2.1/lib/active_support/dependencies.rb:274:in `require': cannot load such file -- rack/handler/start (LoadError)
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/activesupport-4.2.1/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/activesupport-4.2.1/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/activesupport-4.2.1/lib/active_support/dependencies.rb:274:in `require'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/rack-1.6.4/lib/rack/handler.rb:78:in `try_require'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/rack-1.6.4/lib/rack/handler.rb:16:in `get'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/rack-1.6.4/lib/rack/server.rb:290:in `server'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/server.rb:125:in `print_boot_information'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/server.rb:75:in `start'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:80:in `block in server'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:in `tap'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:75:in `server'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /Users/CQ/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/railties-4.2.1/lib/rails/commands.rb:17:in `<top (required)>'
from bin/rails:8:in `require'
from bin/rails:8:in `<main>'

【问题讨论】：

标签： ruby-on-rails ruby rbenv

【解决方案1】：

命令只有rails server或rails s。

见：http://guides.rubyonrails.org/command_line.html#rails-server

【讨论】：