user@Lap:~$ sudo aptitude install build-essential git-core curl
user@Lap:~$ bash < <( curl http://rvm.beginrescueend.com/releases/rvm-install-head )
hoops.... this is not valid anymore, now:
bash < <(curl -s https://rvm.beginrescueend.com/install/rvm)
From there you can install any version of ruby and different gemset.
Before using rvm command, you need to add this line to your .bashrc (at the end of the file)
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"
Not any more! this is now included in the install(15/09/2011)
Then open new terminal type "rvm"
I like to use ruby enterprise (ree in short for rvm)
before to install ree let's install dependencies with the following command
user@Lap:~$ sudo aptitude install build-essential bison openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-0 libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev
Install ruby enterprise
user@Lap:~$ rvm install ree
Installing Ruby Enterprise Edition from source to: /home/user/.rvm/rubies/ree-1.8.7-2011.01
ree-1.8.7-2011.01 - #fetching (ruby-enterprise-1.8.7-2011.01)
use the install ree
user@Lap:~$ rvm use ree
then install the gem you want the usual way
user@Lap:~$ gem install name_of_gem
user@Lap:~$ gem install rails
Note: by default the gems are install in the global gemset but you are free to create different gemset with "rvm gemset create gemset_name"
Reference: RVM site