Install Rails in Ubuntu with RVM

Before installing rvm first of all you need to install a latest version of git in your system.
Run this command in the terminal

sudo aptitude build-dep git-core

Then run the command 

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

to install rvm in your machine.
Now run the command

echo '[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" 

# Load RVM function' >> ~/.bash_profile

To load RVM into your shell sessions as a function.

Now reload the bash with

source .bash_profile

If installation and configuration were successful, RVM should now load whenever you open a new shell. This can be tested by executing the following command which should output 'rvm is a function' as shown below.  

type rvm | head -1

 Now install ruby with rvm with this comand

rvm install 1.9.2-p290

where 1.9.2-p290 is ruby version that we want to install.


now make ruby 1.9.2 your default ruby for the system with this command

rvm use 1.9.2 --default

Now install rails with 

gem install rails --no-ri --no-rdoc

if you get the following error

ERROR:  Loading command: install (LoadError)
    no such file to load -- zlib
ERROR:  While executing gem ... (NameError)
    uninitialized constant Gem::Commands::InstallCommand
then you must install zlib package. Use the following commands if above error shows up

$ rvm pkg install zlib
$ rvm remove 1.9.2
$ rvm install 1.9.2 --with-zlib-dir=$rvm_path/usr

here --no-ri --no-rdoc  will not install ri and rdoc documentation.