Re: changing the JVM

Hi -

Preston_Wade wrote:

> I was working on setting up the tomcat server from the rhaps beta CD.
> I would like to configure it to use another JVM.  I tried most of the
> usually ways you might do this but it didn't seem to work.  Is their
> something different about the way tomcat was build for rhaps?

There is some confusion.  The tomcat RPM included on the CD was compiled
with gcj to object code, so no traditional JVM is used.  The jonas RPM
includes a bundled matching version of tomcat, run under some JVM of your
choice.  I attach below a copy of the release notes on the CD, which
describes this in some detail.


============

Red Hat Application Server - notes for the beta release

This beta release includes several software packages intended for
installation on top of a Red Hat Enterprise Linux 3 U1 system.
These packages include Tomcat, for running Servlet/JSP web
applications, and JoNAS, for running J2EE-based web applications.
These are discussed separately below.

* Tomcat

This version of Tomcat and its dependencies have been compiled to
native code using the GNU gcj compiler, specifically the gcj-ssa
technology preview package included in RHEL3.  This means that no JVM
is required to run the programs.

Tomcat can be started, stopped, and configured to start
automatically, either from the command line (using the commands
'service tomcat [start|stop|restart]' and 'chkconfig tomcat [on|off]')
or from within the Red Hat Service Configuration Tool (from the main
menu, select System Settings -> Server Settings -> Services).  It is
possible to run multiple Tomcat servers on the same machine, as
detailed in /usr/share/doc/tomcat-4.1.27/README.multiple.

Tomcat is configured to use the AJP 1.3 connector module mod_jk2 by
default.  After installing and starting the Tomcat server, you may need
to restart httpd in order for it to load mod_jk2.  Once this is done,
you should be able to browse the example web application by pointing
your browser at the http://localhost/examples/ page.

Tomcat uses the following files and directories:

   /etc/tomcat/server.xml -- Main configuration file.  Edit this if you
     need to add or modify connectors and realms.

   /etc/tomcat/tomcat-users.xml -- User database file.  Edit this to
     add or modify users and roles if you are using the UserDatabase
     realm (the default).

   /etc/sysconfig/tomcat -- Red Hat specific configuration settings.

   /var/lib/tomcat/ -- Directory from which web applications are loaded.

   /etc/logrotate.d/tomcat -- Log rotation configuration settings.  You
     will not normally need to edit this.

   /var/log/tomcat/ -- Directory in which logfiles are written.

   /usr/share/tomcat/common/
   /usr/share/tomcat/server/
   /usr/share/tomcat/shared/ -- Directories into which classfiles and
     jars can be placed to make them available either to all webapps
     (shared), to the server only (server), or to both the server and
     all webapps (common).

mod_jk2 uses the following file:

   /etc/httpd/conf/workers2.properties -- Main configuration file.
     Edit this to add or modify mappings from the webserver to the
     servlet container.

Most server configuration and webapp management tasks can be performed
with the admin and manager web applications respectively.  To enable
them, you must do the following:

   1) Add either or both of the following mappings to mod_jk2's
      configuration file /etc/httpd/conf/workers2.properties and
      restart httpd.

        [uri:/admin/*]
        info=Map the Administration web application

        [uri:/manager/*]
        info=Map the Manager web application

   2) Add a user with the admin and/or manager roles (as required) to
      Tomcat's user database file /etc/tomcat/tomcat-users.xml and
      restart tomcat.

        <user name="whatever" password="PaSsW0Rd" roles="admin,manager"/>

   3) Point your browser at either http://localhost/admin/ (for the
      admin webapp) or http://localhost/manager/html (for the manager
      webapp).

Note that the Tomcat server runs under the tomcat user, which by
default cannot write to either the configuration or the webapps
directories (this limits the damage that a compromised web application
could do).  If you wish to use the manager web application fully or
the admin web application at all, you must either set the ownership and
permissions of the relevant directories yourself or set the relevant
options in /etc/sysconfig/tomcat and restart tomcat.


* Jonas

This version of ObjectWeb JOnAS relies on an installed JVM, such as
those by Sun, IBM, or BEA. (Unlike tomcat which is gcj-compiled, jonas
runs in JVM-interpreted mode.)

Being a typical J2EE application server, jonas relies on a relational
database backend.  This package requires that the rh-postgresql server
be installed, but creates a separate database instance to serve only
jonas.  This new database instance is configured to start and stop
automatically with jonas, puts its data files under
/var/lib/jonas/pgsql, and listens to localhost on TCP port 5433.  This
way it does not interfere with any existing postgresql databases on the
server.  In jonas, it is already configured as the "jdbc_1" datasource
in JNDI.

The entire jonas suite runs under a new "jonas" system user.  You can
activate the server using "/sbin/service jonas start" as is typical of a
network service.  It is configured with its internal servlet engine to
listen for HTTP traffic on port 8080.  Visit
http://localhost:8080/ after installation and jonas startup to
administer and interact with jonas.

The jonas-examples package includes some sample web applications.  A
few of these are compiled and ready for deployment (to make them
accessible to remote web users).  You can use the jonas administrative
web interface (http://.../jonasAdmin/, "Deployments" frames).  After
deployment, you can interact with these samples using the appropriate
web URL prefix.  Other examples require you to download some source
code from the internet.  See /var/lib/jonas/examples.

To build or manage jonas applications using the command line, you need
to set a variety of environment variables:
         JAVA_HOME=`cat /etc/sysconfig/java`
         JONAS_ROOT=/var/lib/jonas
         PATH=${PATH}:${JAVA_HOME}/bin:${JONAS_ROOT}/bin/unix

If necessary, use "classic-ant" as the compilation driver instead of
"ant", because the latter is gcj-compiled on RHEL3 and is not suitable
for jonas.  It may be necessary to use the "su jonas" system command
to deposit .ear/.war/.jar files under jonas installation tree, due to
file system permissions.

More general documentation on use of, and programming with, jonas is
available under /usr/share/doc/jonas-3.3, including a printable PDF.
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