What is the correct target for the JAVA_HOME environment variable for a Linux OpenJDK Debian-based distribution?

In Windows, JAVA_HOME must point to the JDK installation folder (so that JAVA_HOME/bin contains all executables and JAVA_HOME/libs contains all default jar libraries).

If I download Sun's JDK bundle and installs it in Linux, it is the same procedure.

However, I need to use Kubuntu's default OpenJDK package. The problem is that all executables are placed in /usr/bin. But the jars are placed in /usr/share/java. Since they are not under the same JAVA_HOME folder I'm having trouble with Grails and maybe there will be trouble with other applications that expect the standard Java structure.

1. If I use:

   JAVA_HOME=/usr
   

   All applications and scripts that want to use any Java executable can use the standard procedure call $JAVA_HOME/bin/executable. However, since the jars are in a different place, they are not always found (example: in grails I'm getting ClassDefNotFound for native2ascii).

2. On the other hand, if I use:

   JAVA_HOME=/usr/share/java
   

   None of the Java executables (java, javac, etc.) can be found.

So, what is the correct way of handling the JAVA_HOME variable in a Debian-based Linux?

Thanks for your help, Luis

What finally worked for me (Grails now works smoothly) is doing almost like Steve B. has pointed out:

JAVA_HOME=/usr/lib/jvm/default-java

This way if the user changes the default JDK for the system, JAVA_HOME still works.

default-java is a symlink to the current JVM.

If you use alternatives to manage multiple java versions, you can set the JAVA_HOME based on the symlinked java (or javac) like this:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

The standard Ubuntu install seems to put the various Java versions in /usr/lib/jvm. The javac, java you find in your path will softlink to this.

There's no issue with installing your own Java version anywhere you like, as long as you set the JAVA_HOME environment variable and make sure to have the new Java bin on your path.

A simple way to do this is to have the Java home exist as a softlink, so that if you want to upgrade or switch versions you only have to change the directory that this points to - e.g.:

/usr/bin/java --> /opt/jdk/bin/java,

/opt/jdk --> /opt/jdk1.6.011