Tomcat Mechanics

Common Variables
Configuration Files
Filesystem Locations
Operational Scripts
Classpath Usage
References

Articles in this series

Common Variables

Installing Tomcat generically (non distribution packaging) is straight forward; download the appropriate archive and unpack it. Once unpacked there are several environment variables commonly referred to by most Tomcat admins:

Variable	Default	Description
`CATALINA_HOME`	(none)	The main directory that represents the unpacked archive
`CATALINA_BASE`	`$CATALINA_HOME`	(Optional) Base directory for resolving dynamic portions of a Catalina installation
`CATALINA_OUT`	`$CATALINA_BASE/logs/catalina.out`	(Optional) Full path to a file where stdout and stderr will be redirected
`CATALINA_OPTS`	(none)	(Optional) Java runtime options used when the "start" command is executed
`CATALINA_TMPDIR`	`$CATALINA_BASE/temp`	(Optional) Temporary directory the JVM should use (java.io.tmpdir)
`JAVA_HOME`	(none)	Points at the Java Development Kit installation
`JRE_HOME`	`$JAVA_HOME`	Points at the Java Runtime Environment installation
`JAVA_OPTS`	(none)	(Optional) Java runtime options used when the "start" or "stop" command is executed

Configuration Files

Selected configuration files of the most interest:

File	Function
`conf/server.xml`	The main configuration file where most items are configured
`conf/logging.properties`	Configuration for the logging infrastructure (`juli`, `log4j`, etc.)
`conf/web.xml`	Common to all web application deployments (.jsp servlet mappings, mime types, etc.)
`conf/catalina.policy`	Controls security policies when Java is started with `-security`
`conf/catalina.properties`	Controls class loading order and behaviour
`conf/context.xml`	Contexts that will be loaded for every web application (sets `WEB-INF/web.xml` up)
`conf/tomcat-users.xml`	User roles that can be used with various internal security classes

Filesystem Locations

Common

Common subdirectories within the unpacked Tomcat directory for all versions:

Directory	Purpose
`bin/`	Executable scripts such as `catalina.sh`, `startup.sh` and `shutdown.sh`
`conf/`	Configuration files such as `server.xml`, `web.xml` and `logging.properties`
`logs/`	Default directory for logfiles
`temp/`	Various temporary files as needed (`java.io.tmpdir`)
`webapps/`	Location for .war (web archive) or unpacked web applications
`work/`	Location where .jsp files are pre-compiled

Tomcat 6 and above

Directory	Purpose
`lib/`	Fundamental .jar (java archive) files for Tomcat operation common directory

Tomcat 5 and below

Directory	Purpose
`common/`	Classes visible to both internal Tomcat and all web applications
`common/lib/`	Classes and resources in .jar format
`common/il8n/`	Translation .jar files
`common/classes/`	Unpacked classes and resources
`common/endorsed/`	Deployment specific .jar files
`server/`	Classes visible to internal Tomcat only (Catalina)
`server/lib/`	Classes and resources in .jar format
`server/classes/`	Unpacked classes and resources
`server/webapps/`	Core web applications for management such as `host-manager` and `manager`
`shared/`	Classes visible to all web applications
`shared/classes/`	Unpacked classes and resources
`shared/libs/`	Classes and resources in .jar format

Operational Scripts

Some of the commonly used scripts in $CATALINA_HOME/bin:

Script	Function
`catalina.sh`	The main script for starting/stopping Tomcat
`startup.sh`	Resolves symlinks and launches `catalina.sh start $@`
`shutdown.sh`	Resolves symlinks and launches `catalina.sh stop $@`
`version.sh`	Resolves symlinks and launches `catalina.sh version $@`
`daemon.sh`	`stop`
`configtest.sh`	Resolves symlinks and launches `catalina.sh configtest $@` (Tomcat 7 and above)

Classpath Usage

The script catalina.sh overwrites the standard $CLASSPATH environment variable common to java use; the CLASSPATH is first nulled then constructed manually. It loads scripts and files in this order common to all versions:

$CATALINA_BASE/bin/setenv.sh
$CATALINA_HOME/bin/setclasspath.sh
$CATALINA_HOME/bin/bootstrap.jar

From this point onward the classes are loaded internally within Tomcat's java code and varies depending on version; see the Classloaders section of the References for links to each version's documentation.

References

Classloaders

Resources

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