in above list CATALINA_HOME and JAVA_HOME is mandatory environment variables. all others are optional and its can be calculated using CATALINA_HOME.
CATALINA_HOME - this environment variable should point to tomcat base folder, where tomcat binary are installed/extracted. so based on CATALINA_HOME we can get bin and lib folder
CATALINA_BASE - If we not specified then CATALINA_HOME value is set. This variable pointed to configuration and webapps folder. Based on this variable server uses conf, logs, temp, webapps, work folders.
Usual ways to run the tomcat is only set CATALINA_HOME environment variable. and run the startup.sh script file. this startup.sh file automatically calculate and assign the values of other variables what we are not set.
startup.sh file set the environment variable and then call catalina.sh file. this files is read CATALINA_BASE value and attach conf i.e $CATALINA_BASE/conf folder and get server.xml. this file is heart of tomcat. it contains all configuration information. like which tomcat uses as shoutdown port, connector post, host name, application folder ,.. for example usually tomcat uses 8080 is a connector port, so we can access http://localhost:8080/
if we set the $CATALINA_BASE explicitly then tomcat uses our variable to search and get the server.xml file from our target place, what we specified in CATALINA_BASE.
this is trick to run multiple tomcat in single machine. we don't change CATALINA_HOME value. we need to change CATALINA_BASE value before start/shutdown the tomcat.
create one folder named "tomcat-instance1" anywhere, and copy conf, temp, webapps folder from CATALINA_HOME folder and change conf/server.xml file in tomcat-instance1. we need to change 3 port shutdown port, connector port and ajp port.
shutdown port - this port is used for shutdown the tomcat. when we call the shutdown.sh script they send signal to shutdown port. this port listen by tomcat java process. if signal is received the that process then its cleanup and exit by itself.
connector Port -This port is actual port to expose the application to outside client.
ajp port - this port is used to apache httpd server communicate to tomcat. this port used when we setup load balanced server.
see the sample server.xml file
so we change these three port to different number, because once this port is binded then other process can't bind it again. so wee bind different port. so tomcat-instance1/conf/server.xml file i configured server port =8105, connector port = 8181, ajp port = 8109.
now we can create two script file for startup and shutdown the tomcat-instance1. startup-instance1.sh export CATALINA_BASE= /home/ramki/tomcat-instance1 cd $CATALINA_HOME/bin ./startup.sh
here we explicitly set the CATALINA_BASE variable and point to new tomcat-instance1
the we go to CATALINA_HOME/bin folder because all binary for running tomcat is still present in CATALINA_HOME folder then startup/shutdown the script.
Based on above technique we can create many instance folder and change conf/server.xml file port values and run that instance with own newly created script files.
Java Experience created a small utility for automatically generate the multiple tomcat instances in Windows/Linux Systems. Check Here