如果是Ubuntu系统，先安装编译环境

sudo apt-get install build-essential

sudo apt-get install zlib1g

sudo apt-get install zlib1g-dev

1.在终端运行:

$ bash <

$ echo '[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # Load RVM function' >> ~/.bash_profile

2.查看可用的安装列表

$ rvm list known

# MRI Rubies

[ruby-]1.8.6[-p420]

[ruby-]1.8.6-head

[ruby-]1.8.7[-p352]

[ruby-]1.8.7-head

[ruby-]1.9.1-p378

[ruby-]1.9.1[-p431]

[ruby-]1.9.1-head

[ruby-]1.9.2-p180

[ruby-]1.9.2[-p290]

[ruby-]1.9.2-head

[ruby-]1.9.3-preview1

[ruby-]1.9.3-rc1

[ruby-]1.9.3[-p0]

[ruby-]1.9.3-head

ruby-head

# GoRuby

goruby

# JRuby

jruby-1.2.0

jruby-1.3.1

jruby-1.4.0

jruby-1.6.1

jruby-1.6.2

jruby-1.6.3

jruby-1.6.4

jruby[-1.6.5]

jruby-head

# Rubinius

rbx-1.0.1

rbx-1.1.1

rbx-1.2.3

rbx-1.2.4

rbx[-head]

rbx-2.0.0pre

# Ruby Enterprise Edition

ree-1.8.6

ree[-1.8.7][-2011.03]

ree-1.8.6-head

ree-1.8.7-head

# Kiji

kiji

# MagLev

maglev[-head]

maglev-1.0.0

# Mac OS X Snow Leopard Only

macruby[-0.10]

macruby-nightly

macruby-head

# IronRuby -- Not implemented yet.

ironruby-0.9.3

ironruby-1.0-rc2

ironruby-head

3.选择某个版本进行编译安装

$ rvm install 1.9.2

4.选择某个版本为默认版本

$ rvm --default use 1.9.2

Using /home/deploy/.rvm/gems/ruby-1.9.2-p290

$ ruby -v

ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux]

$ rvm list

rvm rubies

=> ruby-1.9.2-p290 [ i686 ]

5.创建gemset, 可以安装多个版本的rails, 互不影响

# 创建rails 3.1.1 gemset, 目录最新版本是3.1.3

$ rvm gemset create rails311

'rails311' gemset created (/home/deploy/.rvm/gems/ruby-1.9.2-p290@rails311).

$ rvm gemset list

gemsets for ruby-1.9.2-p290 (found in /home/deploy/.rvm/gems/ruby-1.9.2-p290)

global

rails311

$ rvm --default ruby-1.9.2-p290@rails311

$ rvm gemset list

gemsets for ruby-1.9.2-p290 (found in /home/deploy/.rvm/gems/ruby-1.9.2-p290)

global

=> rails311

6.安装rails

$ gem install rails -v=3.1.1 --no-rdoc --no-ri

$ rails -v

Rails 3.1.1

PS:1-6步骤是可以用在CentOS上的，只是我当时的桌面环境是Ubuntu，没有编译环境，所以前面那段提了一下