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First, extract the java-side binary to a temporary directory. The following assumes it was extracted to /tmp/mod-cluster
Your next step depends on whether your target server is JBoss AS or JBossWeb/Tomcat.
You don't need to do anything to install the java-side binaries in AS 6.x; it's part of the AS distribution's default, standard and all configurations.
Assuming $JBOSS_HOME indicates the root of your JBoss AS install and that you want to use mod_cluster in the AS's all config:
cp -r /tmp/mod-cluster/mod-cluster.sar $JBOSS_HOME/server/all/deploy
Assuming $CATALINA_HOME indicates the root of your JBossWeb or Tomcat install:
cp -r /tmp/mod-cluster/JBossWeb-Tomcat/lib/* $CATALINA_HOME/lib/
TODO