How to install and setup Oracle JAVA JDK in CentOS 6.4

The machine was running the CentOS 6.4 GNU/Linux distribution and the installation of JAVA JDK was fairly straight forward.
But, I wanted to write this down so that it serves as a proper how-to installation of Oracle’s JAVA in CentOS 6.4. The procedure should be almost (if not completely) the same for CentOS 5 and distros alike .
Ok, enough said. The tutorial is split into the following sections:

1. Update the system
2. Remove any installed versions
3. Download JAVA JDK6 or JDK7
4. Install JAVA JDK6 or JDK7
5. Set-up JAVA JDK6 or JDK7
6. Confirm JAVA JDK6 or JDK7 installation

1. The first thing I’ve done was to make sure the CentOS 6.4 system is fully up-to-date, so I ran:

# yum update

2. Once the update completed, I then checked the system for any other installed JAVA packages using:

# rpm -qa | grep -E '^open[jre|jdk]|j[re|dk]'

there was the ‘java-1.6.0-openjdk-1.6.0.0-1.56.1.11.8.el6_3.i686‘ package already installed so I removed it by running:

# yum remove java-1.6.0-openjdk

3. The next step was to go and download the required JAVA JDK package for the system I was working on. It was a 32 bit CentOS 6.4 so I needed to get the 32 bit JAVA JDK package from Oracle’s JAVA download page.
Note that I needed to install an older version of JAVA JDK since it was specific to the software I was setting up.
Download JAVA JDK6 at:
http://www.oracle.com/technetwork/java/javase/downloads/jdk6u35-downloads-1836443.html
Download JAVA JDK7 at:
http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html
4. Once the JAVA JDK package got downloaded I proceeded with installing the package.
a) Installing the JAVA JDK6 package in CentOS 6.4

set executable bit using:

# chmod +x jdk-6u35-linux-i586-rpm.bin

and installed the JAVA JDK6 package by running:

# ./jdk-6u35-linux-i586-rpm.bin

b) Installing the JAVA JDK7 package in CentOS 6.4

# rpm -Uvh jdk-7u15-linux-i586.rpm

5. Once the JAVA JDK package is installed I then needed to configure it on the system using the `alternatives` command. This is in order to tell the system what are the  default commands for JAVA. Most _sys_admins_ aren’t aware about this and I think that it is a vital part when setting the JAVA package.
a) Setting up the JAVA JDK6 package

# alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_35/jre/bin/java 20000 # alternatives --install /usr/bin/jar jar /usr/java/jdk1.6.0_35/bin/jar 20000 # alternatives --install /usr/bin/javac javac /usr/java/jdk1.6.0_35/bin/javac 20000 # alternatives --install /usr/bin/javaws javaws /usr/java/jdk1.6.0_35/jre/bin/javaws 20000

# alternatives --set java /usr/java/jdk1.6.0_35/jre/bin/java # alternatives --set javaws /usr/java/jdk1.6.0_35/jre/bin/javaws # alternatives --set javac /usr/java/jdk1.6.0_35/bin/javac # alternatives --set jar /usr/java/jdk1.6.0_35/bin/jar

this set the default commands for JAVA JDK7 and listing the ‘/etc/alternatives/’ directory showed the following:

# ls -lA /etc/alternatives/ total 0 lrwxrwxrwx. 1 root root 29 Feb 22 03:39 jar -> /usr/java/jdk1.6.0_35/bin/jar lrwxrwxrwx. 1 root root 34 Feb 22 03:39 java -> /usr/java/jdk1.6.0_35/jre/bin/java lrwxrwxrwx. 1 root root 31 Feb 22 03:39 javac -> /usr/java/jdk1.6.0_35/bin/javac lrwxrwxrwx. 1 root root 36 Feb 22 03:39 javaws -> /usr/java/jdk1.6.0_35/jre/bin/javaws

b) Setting up the JAVA JDK7 package

# alternatives --install /usr/bin/java java /usr/java/jdk1.7.0_15/jre/bin/java 20000 # alternatives --install /usr/bin/jar jar /usr/java/jdk1.7.0_15/bin/jar 20000 # alternatives --install /usr/bin/javac javac /usr/java/jdk1.7.0_15/bin/javac 20000 # alternatives --install /usr/bin/javaws javaws /usr/java/jdk1.7.0_15/jre/bin/javaws 20000

# alternatives --set java /usr/java/jdk1.7.0_15/jre/bin/java # alternatives --set javaws /usr/java/jdk1.7.0_15/jre/bin/javaws # alternatives --set javac /usr/java/jdk1.7.0_15/bin/javac # alternatives --set jar /usr/java/jdk1.7.0_15/bin/jar

this set the default commands for JAVA JDK7 and listing the ‘/etc/alternatives/’ directory showed the following:

# ls -lA /etc/alternatives/ total 0 lrwxrwxrwx. 1 root root 29 Feb 22 03:39 jar -> /usr/java/jdk1.7.0_15/bin/jar lrwxrwxrwx. 1 root root 34 Feb 22 03:39 java -> /usr/java/jdk1.7.0_15/jre/bin/java lrwxrwxrwx. 1 root root 31 Feb 22 03:39 javac -> /usr/java/jdk1.7.0_15/bin/javac lrwxrwxrwx. 1 root root 36 Feb 22 03:39 javaws -> /usr/java/jdk1.7.0_15/jre/bin/javaws

6. Finally I verified the installed version of JAVA via:

# java -version java version "1.7.0_15" Java(TM) SE Runtime Environment (build 1.7.0_15-b03) Java HotSpot(TM) Client VM (build 23.7-b01, mixed mode, sharing)

and

# java -version java version "1.6.0_35" Java(TM) SE Runtime Environment (build 1.6.0_35-b10) Java HotSpot(TM) Server VM (build 20.10-b01, mixed mode)

I know this how-to will serve me as a quick reference for installing JAVA in the future and I truly hope this will help someone else too.