Running a Container that is to be Debugged

This topic describes how to run a base image and volume mount an application's classes and debug files so that you can debug the application.

When you run the container, you must make sure that the docker run or podman run command specifies the following in addition to any parameters that you would normally specify:

• A java command with remote debugging options to overwrite the default command for the container. This means that when the container runs it starts the process that is required to enable remote debugging.
• The port that the container will listen on. If using DHCP or TCP tunneling in the container, the port must be specified by an EXPOSE command in the Dockerfile that was used to create the image

For example, the following is a docker run command you could use to run the JVM COBOL Hello World project supplied as a container demonstration:

docker run  -p 8000 --rm
--cap-add=SYS_PTRACE 
--name helloworld-x64-debug 
-v /home/user/workspace/simpleproj/New_Configuration.bin:/home/root_docker/app 
--workdir /home/root_docker/app 
-it microfocus/vcdevhub:rhel7_8.0_x64_pu1_login
java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000 com.microfocus.example.Program1

The parameters specified in the above docker run command are as follows:

-p 8000

Publishes port number 8000.

--rm

Specifies that the container is to be automatically removed when it finishes running.

--name helloworld-x64-debug

Specifies the name to be used for the container.

--cap-add=SYS_PTRACE

Allows debugging inside a Linux container.

-v /home/user/workspace/simpleproj/New_Configuration.bin:/home/root_docker/app

Mounts the local folder /home/user/workspace/simpleproj/New_Configuration.bin into the folder /home/root_docker/app in the container.

--workdir /home/root_docker/app

Sets the working directory for the container. This must be the same folder that is specified by the -v parameter.

-it

Specifies that the container runs interactively.

microfocus/vcdevhub:rhel7_5.0_x64_pu10_login

Specifies the name of the image to run.

java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000 com.microfocus.example.Program1

Specifies the java command that enables remote debugging for the class com.microfocus.example.Program1 on port 8000.

Listening for transport dt_socket at address: 8000