Ruby on Rails Session 1: How to Build a Ruby on Rails on the Ubuntu.

About Ruby on Rails

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

Step One— Install Ruby with RVM

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.

Step Two—Install Ruby

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

Step Three—Install RubyGems

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

Step Four—Install Rails

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下安装rails时，我尝试了以下命令:

sudo apt-get install ruby

sudo gem install rails

结果在安装rails时得到了如下错误

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

上网搜索了一番，找到原因说是没有安装 build-essential,

linux操作系统上面开发程序，光有了gcc 是不行的
它还需要一个 build-essential软件包
作用是提供编译程序必须软件包的列表信息

也就是说编译程序有了这个软件包
它才知道头文件在哪才知道库函数在哪
还会下载依赖的软件包最后才组成一个开发环境
当然 build-essential包安装时需要的依赖包有些你用不上

没有管用，安装rails依然出现上面错误

由于 mkmf.rb 并没有包含在 Debian 的 Ruby 包里面，需要安装相应的 dev 包，所以执行sudo apt-get install ruby-dev 然后安装rails，成功安装！

-- source to network.