Sakai installations should always be accompanied by a fresh install of Tomcat. It provides a clean environment that simplifies troubleshooting if problems are encountered during the startup phase.
Sakai 2.6 out-of-the box (OOTB) will not run inside Tomcat 6.0+.
The Apache Tomcat servlet container provides an ideal environment for running Sakai as a web application. Tomcat implements both the Java Servlet and JavaServer Pages (JSP) specifications and can be run in standalone mode or in conjunction with a web application server such as the Apache HTTP server or JBoss. Sakai 2.6 works with the Tomcat 5.5 series. We recommend Tomcat 5.5.33 in order to avoid certain Tomcat security vulnerabilities present in earlier releases. Note however, that using Tomcat 5.5.27+ requires the addition of a JAVA_OPTS parameter (see below). Sakai 2.6 is not compatible with Tomcat 6.0+.
Tomcat can be downloaded as a binary install from http://archive.apache.org/dist/tomcat/tomcat-5/
Choose the core distribution. Windows users have the option of downloading either a Windows Service Installer .exe or a binary *.zip archive. We recommend the *.zip archive over the installer because configuration and log viewing are easier. You can later convert the .zip install into a service install by running /bin/service.bat (see below for more details).
Unpack the Tomcat archive into your installation directory of choice, e.g. /opt/. Unix/Mac users should create a symbolic link (e.g., ln -s apache-tomcat-5.5.33) while Windows users should simply rename the base Tomcat directory to /tomcat to simplify the path.
Tomcat pathnames
Windows users should ensure that the Tomcat path includes no spaces as this causes errors with JavaServer Faces (JSF) tools in Sakai.
Good: C:\opt\tomcat\, C:\sakaistuff\installs\tomcat\ 
Bad: C:\program files\tomcat\, C:\opt\apache tomcat 5.5.33\
Tomcat permissions
Unix/Mac users should make sure that they have write permissions to the Tomcat servlet container files and directories before proceeding or startup permission errors may occur.
Tomcat 5.5.27+ and strict quote escaping
Tomcat 5.5.27+ enforces strict quote escaping which causes run-time errors in certain Sakai tools that use the JavaServer Faces (JSF) UI rendering framework. See https://issues.apache.org/bugzilla/show_bug.cgi?id=45015 for more details. If you deploy Sakai using Tomcat 5.5.27+ add the following parameter to your JAVA_OPTS environment setting:
-Dorg.apache.jasper.compiler.Parser.STRICT_QUOTE_ESCAPING=false
Tomcat JDK 1.4 Compatibility Package
Do not download and install the JDK 1.4 Compatibility Package. Sakai 2.6 will not run should you install it.