• Installed RVM with multiple Rails version in fresh installation of Ubuntu 10.04
• This tutorial is for single use only means not root (i.e. root@gloscon-desktop:~# ) 

step-0

Open terminal by pressing Cltr+Altr+T OR

From menu Applications -> Accessories -> Terminal

step-1

$ apt-get install curl git-core build-essential zlib1g-dev libssl-dev libreadline5-dev

step-2

$ bash < <(curl -s https://rvm.beginrescueend.com/install/rvm)

OR 

$ curl -s https://rvm.beginrescueend.com/install/rvm -o rvm-installer ; chmod +x rvm-installer ; ./rvm-installer—version latest

OR

$ bash < <(curl -sk https://rvm.beginrescueend.com/install/rvm)

step-3

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

step-4

restart terminal 

step-5

$ rvm | head -1

‘rvm is a function’

step-6

// install Ruby 1.9.2

$ rvm install 1.9.2

$ ruby -v

step-7

// set Ruby 1.9.2 as default 

$ rvm  – -default 1.9.2

step-8

$ gem install rails -v 3.0.3  // default rails for Ruby 1.9.2

$ rails -v

step-9

$ rvm install 1.8.7

// install Ruby 1.8.7

$ gem install rails -v 2.3.2    //default rails for Ruby 1.8.7

$ rails -v

For more about RVM with GEMSET

=> Gemset is create separate workspace for different versions of rails will not conflict multiple rails versions and gems

// for gemset options by following command

$ rvm gemset

// following command create two gemset for Ruby 1.9.2 

$ rvm gemset create rails222 rails310

$ rvm gemset use rails222

// following command install rails 2.2.2 in gemset name rails222

$ gem install rails -v 2.2.2

$ rvm gemset use rails310

// following command install rails 3.1.0 in gemset name rails310

$ gem install rails -v 3.1.0

// to display all gemsets as following command with all Ruby versions

$ rvm list gemsets 

// to swap from one gemset to another with following command

//syntax $ rvm gemset use

$ rvm gemset use rails222

// You can create & use gemset by following single commad

$ rvm use 1.9.2@demo  - -create

$ rvm gemset name

// To set gemset as default by following command

rvm use 1.9.2@demo  – -default 

// Same for another Ruby as follow

$ rvm use 1.8.7

// following command create a gemset for Ruby 1.8.7 

$ rvm gemset create rails238

$ rvm gemset use rails238

// Following command install rails 2.3.8 in gemset name rails238

$ gem install rails -v 2.3.8

$ rvm gemset use rails238

// You can create & use gemset by following single commad

$ rvm use 1.8.7@demo  – -create

// To set gemset as default by following command

rvm use 1.8.7demo  – -default