start-geonetwork.sh is not found

I want to set the heap for Geonetwork and as the doc says, I need to add this line to the start-geonetwork.sh script :

java -Xms1g -Xmx1g -Xss2M -XX:MaxPermSize=128m -Dgeonetwork.dir=/app/geonetwork_data_dir -Dgeonetwork.lucene.dir=/ssd/geonetwork_lucene_dir

Yet I can’t find where this file is located, knowing that Geonetwork is deployed under tomcat.

Can anyone help me find this file?