Hi,
Thanks for posting your question on Q&A. Typically you do not install software in running containers within a kubernetes pod. Instead you use docker build to build a container image based on the instructions contained in a Dockerfile. You then push the built image to a docker registry, such as Azure Container Registry which acts as a repository for container images. In your kubernetes pod definition you can then reference your image and registry. Ideally you don't want to run any additional configuration or installation commands in a running container/pod as the kubernetes API does not know about these steps and is thus not able to reproduce them when scaling or rescheduling pods as would happen in host failure or maintenance.
To use apt
commands you would typically want to use a debian or ubuntu base image.