This support solution is on installing a 32-bit app on a x64 system. Stated on the example of Java Development Kid installed on Fedora x64 bit.



There are three layers that are important when it comes to 32/64bit compatibility:

- Processor

- Operating System

- Application

A 32 bit OS will run on a 32 or 64 bit processor, without any problems.

A 32 bit software on a 64 bit OS works, but could cause difficulties even if the 64 bit systems are backward compatible with the 32 bit counterparts.

To run a 64 bit OS, you need support from its lower level (a 64 bit processor). Therefore a 64 bit OS does not work for a 32 bit CPU.

To run a 64 bit application, you need support from all lower levels (64 bit OS and 64 bit processor).

Linux commands:
Check your processor:

# cat /proc/cpuinfo

Check Kernel/System:

# uname -m

For our example, the perfect solution is to install a 64 bit version of JDK on the Fedora x64 bit operating system.

Here is the How-To-Do:

First thing we need to do is get the JDK installer
JDK Home from Oracle.com

Once we have the installer in our local repository (as root):

chmod a+x  jdk-6u21-linux-x64-rpm.bin./jdk-6u21-linux-x64-rpm.bin

Next, we must add these two lines to the file: /etc/profile

JAVA_HOME=/usr/java/jdk1.6.0_21
pathmunge $JAVA_HOME/jre/bin after

At the end of the line that starts with export, we need to add this our JAVA_HOME variable, so the line should be like this:

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE INPUTRC JAVA_HOME

Then, we need to execute the next statements. Hint: Copy all the lines like if were just one.

export JAVA_HOME=/usr/java/jdk1.6.0_21
export JAVA_ALTERNATIVE_PRIORITY=16021
/usr/sbin/update-alternatives --install /usr/bin/java java $JAVA_HOME/bin/java $JAVA_ALTERNATIVE_PRIORITY
/usr/sbin/update-alternatives --install /usr/bin/javadoc javadoc $JAVA_HOME/bin/javadoc $JAVA_ALTERNATIVE_PRIORITY
/usr/sbin/update-alternatives --install /usr/bin/appletviewer appletviewer $JAVA_HOME/bin/appletviewer $JAVA_ALTERNATIVE_PRIORITY
/usr/sbin/update-alternatives --install /usr/bin/javah javah $JAVA_HOME/bin/javah $JAVA_ALTERNATIVE_PRIORITY
/usr/sbin/update-alternatives --install /usr/bin/javac javac $JAVA_HOME/bin/javac $JAVA_ALTERNATIVE_PRIORITY
/usr/sbin/update-alternatives --install /usr/bin/jar jar $JAVA_HOME/bin/jar $JAVA_ALTERNATIVE_PRIORITY

Then, we export the alternatives:

/usr/sbin/update-alternatives --auto java
/usr/sbin/update-alternatives --auto javadoc
/usr/sbin/update-alternatives --auto appletviewer
/usr/sbin/update-alternatives --auto javah
/usr/sbin/update-alternatives --auto javac
/usr/sbin/update-alternatives --auto jar

To confirm that our installation is successfull:

java -version

Should give us an ouptput like this:

[root@yourMachine]# java -version
java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b02)
Java HotSpot(TM) 64-Bit Server VM (build 16.3-b01, mixed mode)

Further information:
http://www.techsupportalert.com/content/32-bit-and-64-bit-explained.htm

http://wporta.wordpress.com/2010/07/06/installing-jdk-in-fedora-13/