Penrose Server requires a Sun JDK 1.5 for its security libraries. If you are using Red Hat/Fedora/
Centos/Other Linux distros, Sun JDK is may or may not installed. After installing the required JDK, you can add a new entry to alternatives by using this command:

[root@localhost]# alternatives --install /usr/bin/java java /usr/java/jdk1.5.0_11/bin/java 2

NOTE: We assign "2" in above command with the assumption that there is only one JVM installed.

ater this you can easily switch your JVM by issuing this command:

[root@localhost]# alternatives --config java

and pick number "2"