What podman is

Podman is a self-described daemonless container engine for developing and running OCI containers on you linux system. Builds a virtual version of a linux distro inside an SSD or HD.

Use cases

Podman is geared towards running non-native or incompatible software (different distributions Ubuntu/Debian) on CentOS systems.  Podman is typically not used to run server type applications that require open ports and writing to log files (Apache web servers or databases).

Why use it

• Hackers can take advantage of VMs running older versions of Linux with known security vulnerabilities.
• Simplifies the consumption of applications – some legacy applications may not play nice with newer versions/ flavors of linux.
• Because it’s awesome AND open source; It has a great UI and simple to use API.
• You can combine this with buildah to make your own images.

Prerequisites

This tutorial assumes that you have podman io installed on your linux machine. The instructions for such a task can be found here: https://podman.io/getting-started/installation if not already done.

How to Use it: 
Now that your motivated to learn, let’s start with a gentle introduction to the podman API.

Let’s check if there are any images installed –
[user@localhost ~]$ podman images

Well, we don't have any images to play with, so let's pull an image off a repository:
[user@localhost ~] podman pull quay.io/roboxes/centos8

Check images again:
[user@localhost ~] podman images

Now we will test our new environment. First, let’s look at something –
[user@localhost ~] podman ps -a

The table is empty because we haven’t created any containers yet. Let’s create one:
[user@localhost ~] podman run quay.io/roboxes/centos8 /bin/bash

You should see a new prompt:
[root@randomID ~]

While we are here let’s look at the redhat release version:
[root@randomID ~] cat /etc/redhat-release

Let’s exit the container now:
[root@randomID ~] exit

[user@localhost ~] cat /etc/redhat-release

Finally, lets check the session history again:
[user@localhost ~] podman ps -a

Summary

There you have it – you should now know how to pull an image, run and exit the container, check which images you have containerized, and check what processes you’ve run. In the next section, we will talk about building container images from scratch using buildah.

Building an Image from scratch 

Okay, now that we know how to run containers using docker/ podman, we will also gain some familiarity with the buildah api. As a simple model, if you're familiar with object oriented programming, you can think of images as the class, and containers as an object of that class. source: https://github.com/containers/buildah/blob/master/docs/tutorials/01-intr...

First, let’s check something
[user@localhost ~]$ buildah images

There are no images because we haven't made one yet - lets create one using a docker file:
[user@localhost ~] vim Dockerfile
Strike i for insert mode and copy and paste the following:

FROM ubuntu:xenial

ENV LANG=C.UTF-8 LC_ALL=C.UTF-8

RUN apt-get update --fix-missing && \
    apt-get install -y wget bzip2 ca-certificates curl git python-dev gcc build-essential  gnupg lsb-release apt-file && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

ENV TINI_VERSION v0.16.1
RUN wget --quiet https://github.com/krallin/tini/releases/download/v0.16.1/tini -O /usr/bin/tini
# ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini /usr/bin/tini
RUN chmod +x /usr/bin/tini

COPY dockerDemo.py /usr/local/bin/dockerDemo.py

# ENTRYPOINT [ "/usr/bin/tini", "--" ]
ENTRYPOINT ["python", "/usr/local/bin/dockerDemo.py"]
CMD [ "/bin/bash" ]

Strike esc key and then hit type :wq

Now we'd like to make an example program that prints something so we know it's running inside an image.

[user@localhost ~] vim dockerDemo.py
print("I'm running from inside the container.")

Now we can build the image using buildah(enter computers host id for localhost at the end of the command).
[user@localhost ~] buildah --format=docker bud -t localhost/dockerdemo

When your build completes, try running the buildah command we did at the beginning again
[user@localhost ~] buildah images

To run the newly created image, simply run the following buildah command with what was under IMAGE ID for TAG latest:
[user@localhost ~] buildah run -it __yourimageID__ 

And you're done! Congrats, you just built your first image and ran a python script from inside a container of that image.

Wrapping up

You should now be able to create images using buildah, docker, and test them using simple python scripts.