Make it clearer that JAVA_OPTS is about JSVC options

Sounds like a JVM bug: What JVM are you using ? Could you try passing those options directly to "java" to test how it reacts ?

I am using:

java version "1.6.0_16"
Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
Java HotSpot(TM) 64-Bit Server VM (build 14.2-b01, mixed mode)

And I have the same problem with openJDK. It's not java for sure.

Putting in the command line it seems pretty fine:

java -Xmx1024m -enableassertions -server -XX:MaxPermSize=512m -XX:+CMSPermGenSweepingEnabled -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -Djava.awt.headless=true -Dorg.apache.jasper.runtime.BodyContentImpl.LIMIT_BUFFER=true -version
Please use CMSClassUnloadingEnabled in place of CMSPermGenSweepingEnabled in the future
java version "1.6.0_16"
Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
Java HotSpot(TM) 64-Bit Server VM (build 14.2-b01, mixed mode)

Reproduced with OpenJDK / tomcat6 / Ubuntu 9.10

The issue here is that you are not passing java options, but jsvc options.
jsvc accepts -X and -D options and passes them to the underlying JVM. It does not recognize -enableassertions or -server (see man jsvc). It recognizes -ea for -enableassertions though (undocumented, found in 1.0.1 release notes).

Note that OpenJDK uses -server by default so it should not be needed if you used OpenJDK. Not sure about Sun's JVM, but it might have the same default.

So this is not a bug, but maybe we need to document that a little better since the name is misleading (JAVA_OPTS).

This bug was fixed in the package tomcat6 - 6.0.20-8ubuntu1

---------------
tomcat6 (6.0.20-8ubuntu1) lucid; urgency=low

  * Merge from Debian unstable. Remaining changes:
    - debian/control, debian/rules: Do not use 3.0 (quilt) source format yet
  * debian/tomcat6.default: Fix typos in "JSVC" and "remote", missing newline
  * debian/tomcat6.default, debian/tomcat6.init: Handle JSVC_CLASSPATH
    default value the same way as other defaults

tomcat6 (6.0.20-8) unstable; urgency=low

  * Corrected some spelling mistakes in debian/control.
    (Closes: #557377, #557378)
  * Added patches to install the OSGi metadata in some of the jars.
    (Closes: #558176)
  * Updated 03catalina.policy to allow "setContextClassLoader".
    - Fixes a problem where Sun's JVM would fail to generate log-files.
    (Closes: LP: #410379)
  * Updated /etc/default/tomcat6:
    - Clarified that JAVA_OPTS are passed to jscv and not the JVM.
    - Updated the JSP_COMPILER to javac (jikes is not in Debian anymore).
    (Closes: LP: #440685)
  * Use default-jdk and default-jre-headless instead of openjdk in
    (Build-)Depends.
  * Added more alternatives for java implementations to the Depends of
    libservlet2.5-java.
  * Exposed JSVC_CLASSPATH to the configuration file.
    (Closes: LP: #475457)
  * Updated description so it no longer refers to non-existent package.
    (Closes: #559475)
  * Used "set -e" in postinst and postrm instead of passing "-e" to sh
    in the #!-line.
  * Changed to 3.0 (quilt) source format.

tomcat6 (6.0.20-7) unstable; urgency=low

  * New patch fix_context_name.patch:
    - Allow Service name != Engine name. Regression in fix for 42707.
      Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=47316
    - This has been fixed in trunk and will be in 6.0.21
  * Register libservlet2.5-java-doc API with doc-base
  * Fix short description of tomcat6-docs by using "documentation" suffix

tomcat6 (6.0.20-6) unstable; urgency=low

  [ Ludovic Claude ]
  * tomcat6.postinst: set the ownership of files in /etc/tomcat6/
    to root:tomcat6, to prevent an attacker running inside a tomcat6
    instance to change the tomcat configuration
  * debian/policy/02debian.policy: grant access to
    /usr/share/maven-repo/ as it is a valid source of Debian JARs.
    (Closes: #545674)
  * Bump up Standards-Version to 3.8.3
    - add debian/README.source that describes the quilt patch system.
  * debian/control: Add Conflicts on libtomcat6-java with old versions
    of tomcat6-common (Closes: #542397)

  [ Michael Koch ]
  * Replace dh_clean -k by dh_prep.
  * Added Ludovic and myself to Uploaders.
  * Build-Depends on debhelper >= 7.

tomcat6 (6.0.20-5) unstable; urgency=low

  * Fix jsp-api dependency in the Maven descriptors.
  * Put tomcat-juli.jar in /usr/share/java instead of juli.jar.
    This fixes a broken link which prevented tomcat to start
    when logging is turned on, and restores the file layout
    defined in 6.0.20-2.
  * Restore links to the jars in usr/share/tomcat6/lib
  * Change watch to download fresh sources from SVN.
    Should fix wrong encoding in tomcat-i18n-fr/es.jar in the next upstream
    version. (Closes: #522067)
  * Update ...