Many developers encounter this issue when trying to modify Tomcat's startup parameters through /etc/init.d/tomcat6. The key misunderstanding is that Ubuntu's init scripts often override environment variables. Here's why your changes aren't taking effect:

# Common pitfall - environment variables get overwritten
# In /etc/default/tomcat6 you'll find:
JAVA_OPTS="-Djava.awt.headless=true -Xmx128m"

Instead of modifying the init script directly, you should:

1. Edit /etc/default/tomcat6 (the proper location for environment variables)
2. Add your debug parameters to the existing JAVA_OPTS
3. Make sure to preserve existing settings

# Correct way to modify JAVA_OPTS
JAVA_OPTS="$JAVA_OPTS -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n"

After making changes, restart Tomcat and verify:

sudo service tomcat6 restart
ps aux | grep tomcat
netstat -tulpn | grep 8000

In Eclipse, create a new debug configuration:

1. Go to Run → Debug Configurations
2. Create new Remote Java Application
3. Set Host to your server IP
4. Port 8000 (must match address in JAVA_OPTS)
5. Connection Type: Standard (Socket Attach)

• Check firewall settings: sudo ufw allow 8000
• Verify Tomcat is running with your user: ps -ef | grep tomcat
• Examine catalina.out for errors: tail -f /var/log/tomcat6/catalina.out

For production systems, consider using:

CATALINA_OPTS="$CATALINA_OPTS -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n"

This keeps debug settings separate from other Java options.

---

When setting up remote debugging for Tomcat 6 on Ubuntu 10.04, the common approach of modifying JAVA_OPTS in /etc/init.d/tomcat6 often fails because Ubuntu's init scripts use a different mechanism. Here's what actually works:

On Ubuntu systems, Tomcat 6 settings should be configured in:

/etc/default/tomcat6

Add these debug parameters at the end of the file:

JAVA_OPTS="${JAVA_OPTS} -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n"
JAVA_OPTS="${JAVA_OPTS} -Djava.awt.headless=true -Xmx256M"

After saving the file, restart Tomcat:

sudo service tomcat6 restart

Check if the debug port is listening:

sudo netstat -tulpn | grep 8000

You should see output similar to:

tcp6    0    0 :::8000    :::*    LISTEN    1234/java

In Eclipse, create a new debug configuration:

1. Go to Run → Debug Configurations
2. Create new 'Remote Java Application' configuration
3. Set host to your server IP
4. Port: 8000
5. Connection Type: Standard (Socket Attach)

For more control, you can modify the startup script directly:

sudo nano /usr/share/tomcat6/bin/catalina.sh

Find the JPDA_ADDRESS variable and set it to:

JPDA_ADDRESS="8000"
JPDA_TRANSPORT="dt_socket"

Then start Tomcat in debug mode:

sudo /etc/init.d/tomcat6 stop
sudo /usr/share/tomcat6/bin/catalina.sh jpda start

If you still can't connect:

• Check Ubuntu's firewall: sudo ufw status
• Verify SELinux isn't blocking: sudo setsebool -P tomcat_can_network_connect_db 1
• Ensure your debug parameters appear in the process list: ps aux | grep tomcat