BOS Community edition 6.2.2 bundled with tomcat, on a Ubuntu box: startup.sh problem

I'm afraid to be forced to ask the forum for such a "rookie" question: I followed all info in the installation (http://documentation.bonitasoft.com/tomcat-bundle-0), but I'm unable to startup the catalina process: invoking startup.sh results in the following:

Using CATALINA_BASE: /opt/BonitaBpmCommunity

Using CATALINA_HOME: /opt/BonitaBpmCommunity

Using CATALINA_TMPDIR: /opt/BonitaBpmCommunity/temp

Using JRE_HOME: /usr

Using CLASSPATH: /opt/BonitaBpmCommunity/bin/bootstrap.jar

Using CATALINA_PID: /opt/BonitaBpmCommunity/catalina.pid

Usage: catalina.sh ( commands ... )

commands:

debug Start Catalina in a debugger

debug -security Debug Catalina with a security manager

jpda start Start Catalina under JPDA debugger

run Start Catalina in the current window

run -security Start in the current window with security manager

start Start Catalina in a separate window

start -security Start in a separate window with security manager

stop Stop Catalina, waiting up to 5 seconds for the process to end

stop n Stop Catalina, waiting up to n seconds for the process to end

stop -force Stop Catalina, wait up to 5 seconds and then use kill -KILL if still running

stop n -force Stop Catalina, wait up to n seconds and then use kill -KILL if still running

version What version of tomcat are you running?

Note: Waiting for the process to end and use of the -force option require that $CATALINA_PID is defined

I configured Mysql as a db backend (followed istructions @ http://documentation.bonitasoft.com/configure-bonita-your-dbms)

I changed the default password.

I changed the default port 8080 in 22111.

But something is missing, so the catalina doesn't start at all: it doesn't start a new log, no pid

Any ideas.
TIA

bye