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How to Install Hadoop (2.7.3) on Ubuntu (16.04 LTS)

As I am planning to learn Hadoop, I wanted to install Hadoop (2.7.3) on my Ubuntu (16.04 LTS) and I followed the steps mentioned in the documentation on the Apache Hadoop website. I encountered few problems which are mentioned below, spent some time finding solution to them.

Below are the steps I followed and the description of the error is at the end of this post and also I have mentioned what I missed and what caused these errors.


Step 1. Download Hadoop installation file. For Hadoop 2.7.3 version I used the following link 

http://www.apache.org/dyn/closer.cgi/hadoop/common/hadoop-2.7.3/hadoop-2.7.3-src.tar.gzStep 2. (Assuming you have downloaded the file into /home/<username>/Downloads folder

$ tar zxf hadoop-2.7.3-src.tar.gz
This will extract the files into a folder  "hadoop-2.7.3" .

Step 3. I moved the file to /home/<username> folder (many suggest to move it into /usr/local but I prefer to keep it here, may be once I learn more about linux I might get into tha…

Javascript KeyCode Reference table for Event Handling

The post explains Keyboard event handling using javascript.Javascript events are used to capture user keystrokes. Below is a table of key codes for the keys on a multimedia keyboard. If this table is inconsistent with your own findings, please let me know.

Java Script Code to Find Key code

<script language="JavaScript">
document.onkeydown = checkKeycode
function checkKeycode(e) {
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
alert("keycode: " + keycode);
}
</script>


Key Code Reference Table
Key PressedJavascript Key Codebackspace8tab9enter13shift16ctrl17alt18pause/break19caps lock20escape27page up33page down34end35home36left arrow37up arrow38right arrow39down arrow40insert45delete46048149250351452553654755856957a65b66c67d68

Replacing OpenJDK with Oracle JDK in Ubuntu

You can completely remove the OpenJDK and fresh Install Oracle Java JDK by the following steps:
Remove OpenJDK completely by this command:
sudo apt-get purge openjdk-\*Download the Oracle Java JDKhere.
Note: download appropriate file, for example if your system is x64 Ubuntu (i.e, Debian) the download file is named like this: jdk-8u51-linux-x64.tar.gz
To find which version is your OS, check hereCreate a folder named java in /usr/local/by this command:
sudo mkdir -p /usr/local/javaCopy the Downloaded file in the directory /usr/local/java. To do this, cd into directory where downloaded file is located and use this command for copying that file to /usr/local/java/:
sudo cp -r jdk-8u51-linux-x64.tar.gz /usr/local/java/CD into /usr/local/java/ directory and extract that copied file by using this command:
sudo tar xvzf jdk-8u51-linux-x64.tar.gzAfter extraction you must see a folder named jdk1.8.0_51.Update PATH file by opening /etc/profile file by the command sudo nano /etc/profile and past…