Installing ruby on rails (ruby version 1.9.3, rails version 3.2.2) on Ubuntu Lucid LTS 10.04

The post shows a step-by-step installation of the Ruby on Rails on Ubuntu 10.04 LTS.

1. install build essential, github and 

sudo apt-get install build-essential

2. install rvm (which includes ruby 1.9.3 and gem 1.8.19)

bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)
source ~/.bashrc
rvm requirement -- install output required libraries by copy and paste the output text
rvm install 1.9.3  -- it takes a while

3. install rails

copy and paste the text below at the end of ~/.bashrc: 
[[-s "$HOME/.rvm/scripts/rvm"]] && . "$HOME/.rvm/scripts/rvm" 

source $HOME/.bashrc

check the successful installation of rvm:

type rvm | head -1

output should be 'rvm is a function'

gem install rails --include-dependencies

Congratulations! You have successfully installed Ruby on Rails!

Linux and Java: Disk usage, Memory check, JVM virtual memory, Processor Info, Kernel Info

Check disk usage:
df -h

Check file size in a directory
du -sh *


Check memory usage, display total memory in MB:
free -t -m


Set JVM virtual memory:
java -jar -Xms128m -Xmx512m bigapp.jar

Processor Info:
cat /proc/cpuinfo

Kernel version:
uname -r

How to remove ^M from file using VI

Sometimes DOS files have "^M" at the end of each line, which causes problem for perl to read lines correctly.

We can use VI to remove these annoying ^M.

=============Using VI================

Type the following command at the terminal.

vi file_name.txt

Basically vi is the name of a text editor under linux/mac.

After issuing this command, you should be able to see the command window showing the content of the file.

Next step is to remove the annoying ^M at the end of each line.

Type the following command in VI editor. Do not miss the semi-colon at the begining.

:%s/[ctrlkey+v and ctrl-key+M]/\r/g

You should be able to see the following at the left-bottom corner of the command window:

:%s/^V^M/\r/g

The command above is meant to replace ^M with a new line symbol "\n".

Press enter and wait for a while for every occurrence of ^M to be replaced.

Depending on the size of your file, it can take a while and the screen appears frozen.

When the replacing is done, type the following command to save and exit from VI.

:x

Good luck!