运行rails服务器时出错答案

【问题标题】：getting error while runnning rails server运行rails服务器时出错
【发布时间】：2018-07-07 21:12:10
【问题描述】：

/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in 

`require': cannot load such file -- mkmf (LoadError)
    from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
    from extconf.rb:1:in `<main>'


Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.8.6 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/json-1.8.6/ext/json/ext/generator/gem_make.out

An error occurred while installing json (1.8.6), and Bundler cannot continue.
Make sure that `gem install json -v '1.8.6'` succeeds before bundling.

在 Gemfile 中：

 coffee-rails was resolved to 3.2.2, which depends on 
        railties was resolved to 3.2.16, which depends on
          rdoc was resolved to 3.12.2, which depends on
            json

在运行 rails s 时遇到此错误。如何解决它

【问题讨论】：

Why won't bundler install JSON gem?的可能重复
你还没有安装所有的gem。 bundle install 一路走来。重新运行 bundle install 并将完整的错误堆栈跟踪放在这里。
在运行 gem install json -v '1.8.6' 时。收到错误：错误：安装 json 时出错：错误：无法构建 gem 原生扩展。 当前目录：/var/lib/gems/2.4.0/gems/json-1.8.6/ext/ json/ext/generator /usr/bin/ruby2.4 -r ./siteconf20180129-18806-bb4juz.rb extconf.rb mkmf.rb 在 /usr/lib/ruby/include/ruby 找不到 ruby 的头文件。 h extconf failed, exit code 1 Gem 文件将继续安装在 /var/lib/gems/2.4.0/gems/json-1.8.6 中以供检查。结果记录到 /var/lib/gems/2.4.0/extensions/x86-linux/2.4.0/json-1.8.6/gem_make.out
错误：执行 gem 时 ... (Errno::EACCES) 权限被拒绝 @ rb_sysopen - /var/lib/gems/2.4.0/gems/json-1.8.6/tests/test_json。 rb

标签： ruby-on-rails json ruby rubygems

【解决方案1】：

注释 gemfile 的内容并将 ruby 和 rails 更新到最新的稳定版本将解决大部分错误。对我来说，我使用以下提供的步骤重新安装了 ruby 和 rails：

https://www.digitalocean.com/community/tutorials/how-to-install-ruby-on-rails-with-rbenv-on-ubuntu-14-04

【讨论】：