Ruby on Rails is an application stack that PRovides developers with a framework to quickly create a variety of web applications. Ruby on Rails does take a little while to install on a virtual server, but luckily there are a lot of helpful tools to make this process as easy as possible. You can run this tutorial on your droplet as a user with sudo privileges. You can check out how to set that up here: Ubuntu Server Setup

Before we do anything else, we should run a quick update to make sure that all of the packages we download to our VPS are up to date:

sudo apt-get update

Once that's done, we can start installing RVM, Ruby Version Manager. This is a great program that lets you use several versions of Ruby on one server; however, in this case, we will just use it to install the latest version of Ruby on the droplet.

If you do not have curl on your system, you can start by installing it:

sudo apt-get install curl

To install RVM, open terminal and type in this command:

/curl -L https://get.rvm.io | bash -s stable

After it is done installing, load RVM. You may first need to exit out of your shell session and start up a new one.

source ~/.rvm/scripts/rvm

In order to work, RVM has some of its own dependancies that need to be installed. To automatically install them:

rvm requirements

You may need to enter your root passWord to allow the installation of these dependencies.

On occasion the zlib package may be reported as missing. The RVM page describes the issue and the solution in greater detail here.

Once you are using RVM, installing Ruby is easy.

rvm install ruby

The latest ruby is now installed. However, since we accessed it through a program that has a variety of Ruby versions, we need to tell the system to use the version we just installed by default.

rvm use ruby --default

The next step makes sure that we have all the required components of Ruby on Rails. We can continue to use RVM to install gems; type this line into terminal.

 rvm rubygems current

Once everything is set up, it is time to install Rails. To start, open terminal and type in:

gem install rails

This process may take a while, be patient with it. Once it finishes you will have Ruby on Rails installed on your droplet.

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在ubuntu下安裝rails時，我嘗試了以下命令:

sudo apt-get install ruby

sudo gem install rails

結果在安裝rails時得到了如下錯誤

Building native extensions. This could take a while...ERROR: Error installing rails: ERROR: Failed to build gem native extension. /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:13:in `<main>'Gem files will remain installed in /var/lib/gems/1.9.1/gems/atomic-1.1.13 for inspection.Results logged to /var/lib/gems/1.9.1/gems/atomic-1.1.13/ext/gem_make.out上網搜索了一番，找到原因說是沒有安裝 build-essential,

linux操作系統上面開發程序， 光有了gcc 是不行的它還需要一個 build-essential軟件包作用是提供編譯程序必須軟件包的列表信息也就是說 編譯程序有了這個軟件包它才知道 頭文件在哪 才知道庫函數在哪還會下載依賴的軟件包 最后才組成一個開發環境當然 build-essential包 安裝時 需要的依賴包 有些你用不上

沒有管用，安裝rails依然出現上面錯誤

由于 mkmf.rb 并沒有包含在 Debian 的 Ruby 包里面，需要安裝相應的 dev 包，所以執行sudo apt-get install ruby-dev 然后安裝rails，成功安裝！

-- source to network.