Tomcat: The Definitive Guide, 2nd Edition

IBM J9 JDK

IBM has a compatible JDK: J9. Like the Sun JDK, J9 also supports popular operating systems, such as Linux, plus some that Sun doesn't support (e.g., AIX and z/OS). This JVM had the smallest disk installation footprint out of all of the compatible JDKs we tried. You can download its JDK from http://www.ibm.com/developerworks/java/jdk.

Here is how we installed the tar gzipped archive on Linux (as the root user):

# cd /opt
# tar zxvf ˜/ibm-java-sdk-60-linux-x86_64-20070329.tgz
#chmod -R go+rx ibm-java2-x86_64-60
#chown -R root.root ibm-java2-x86_64-60

Once it is installed, set JAVA_HOME and PATH like this:

# JAVA_HOME=/opt/ibm-java2-x86_64-60
#export JAVA_HOME
# PATH=$JAVA_HOME/bin:$PATH
#export PATH

Then, check to make sure your java executable points to the JDK you just installed:

# which java
/opt/ibm-java2-x86_64-60

Here's how it identified itself on one of our Linux computers:

$ java -version
java version "1.6.0-internal"
Java(TM) SE Runtime Environment (build 20070329_01)
IBM J9 VM (build 2.4, J2RE 1.6.0 IBM J9 2.4 Linux amd64-64 jvmxa6460-20070326_12091 (J
IT enabled)
J9VM - 20070326_12091_LHdSMr
JIT  - dev_20070326_1800_dev
GC   - 20070319_AA)