First copy catalina.sh under tomcat to the /etc/init.d/tomcat path
vi /etc/init.d/tomcat
exist
# OS specific support. $var _must_ be set to either true or false.
cygwin=false
darwin=false
os400 = false
hpux=false
Add the following line above
CATALINA_HOME=/opt/tomcat7/
Please refer to the attachment for specific configuration