Exploring and Running Containers

Last updated on 2025-11-12 | Edit this page

Estimated time: 30 minutes

Overview

Questions

  • How do I interact with Podman containers and container images on my computer?

Objectives

  • Use the correct command to see which container images are on your computer.
  • Be able to download new container images.
  • Demonstrate how to start an instance of a container from a container image.
  • Describe at least two ways to execute commands inside a running container.
Callout

Reminder of terminology: container images and containers

Recall that a container image is the template from which particular instances of containers will be created.

Let’s explore our first Podman container. The Podman team provides a simple container image online called hello. We’ll start with that one.

Downloading Podman images

The podman image command is used to interact with Podman container images. You can find out what container images you have on your computer by using the following command (“ls” is short for “list”):

BASH 

$ podman image ls

If you’ve just installed Podman, you won’t see any container images listed.

To get a copy of the hello Podman container image from the internet, run this command:

BASH 

$ podman image pull hello

You should see output like this:

OUTPUT 

Resolved "hello" as an alias (/etc/containers/registries.conf.d/000-shortnames.conf)
Trying to pull quay.io/podman/hello:latest...
Getting image source signatures
Copying blob sha256:1ff9adeff4443b503b304e7aa4c37bb90762947125f4a522b370162a7492ff47
Copying config sha256:83fc7ce1224f5ed3885f6aaec0bb001c0bbb2a308e3250d7408804a720c72a32
Writing manifest to image destination
83fc7ce1224f5ed3885f6aaec0bb001c0bbb2a308e3250d7408804a720c72a32
Callout

Docker Hub

Where did the hello container image come from? If you look carefully in the output when you pulled the image, you will see that it came from the Quay container registry, which is a place to share container images with other people. Specifically, Podman expanded the short container name to quay.io/podman/hello. Other container registries exist, sometimes with differing use cases. Docker Hub is probably the most widely used. Although under the ‘Docker’ name, Docker Hub can be used by any compatible containerization service, including Podman and Singularity. We can get Docker’s version of a hello image by instead pulling docker.io/hello-world.

Challenge

Exercise: Check on Your Images

What command would you use to see if the hello container image had downloaded successfully and was on your computer? Give it a try before checking the solution.

To see if the hello container image is now on your computer, run:

BASH 

$ podman image ls

Note that the downloaded hello container image is not in the folder where you are in the terminal! (Run ls by itself to check.) The container image is not a file like our normal programs and documents; Podman stores it in a specific location that isn’t commonly accessed, so it’s necessary to use the special podman image command to see what Podman container images you have on your computer.

Running the hello container

To create and run containers from named Podman container images you use the podman container run command. Try the following podman container run invocation. Note that it does not matter what your current working directory is.

BASH 

$ podman container run hello

OUTPUT 

!... Hello Podman World ...!

         .--"--.
       / -     - \
      / (O)   (O) \
   ~~~| -=(,Y,)=- |
    .---. /`  \   |~~
 ~/  o  o \~~~~.----. ~~
  | =(X)= |~  / (O (O) \
   ~~~~~~~  ~| =(Y_)=-  |
  ~~~~    ~~~|   U      |~~

Project:   https://github.com/containers/podman
Website:   https://podman.io
Desktop:   https://podman-desktop.io
Documents: https://docs.podman.io
YouTube:   https://youtube.com/@Podman
X/Twitter: @Podman_io
Mastodon:  @Podman_io@fosstodon.org

What just happened? When we use the podman container run command, Podman does three things:

1. Starts a Running Container 2. Performs Default Action 3. Shuts Down the Container
Starts a running container, based on the container image. Think of this as the “alive” or “inflated” version of the container – it’s actually doing something. If the container has a default action set, it will perform that default action. This could be as simple as printing a message (as above) or running a whole analysis pipeline! Once the default action is complete, the container stops running (or exits). The container image is still there, but nothing is actively running.

The hello container is set up to run an action by default – namely to print this message.

Callout

Using podman container run to get the image

We could have skipped the podman image pull step; if you use the podman container run command and you don’t already have a copy of the Podman container image, Podman will automatically pull the container image first and then run it.

Running a container with a chosen command

But what if we wanted to do something different with the container? Let’s use a different container image to explore what else we can do with the podman container run command. One image we could use is ubuntu which provides, as the name suggests, a container running Ubuntu Linux. However, we’re going to run a different type of Linux instead, alpine, because it’s smaller and so the image is quicker to download.

Discussion

Run the Alpine Podman container

Try downloading the alpine container image and using it to run a container. You can do it in two steps, or one. What are they?

What happened when you ran the Alpine Podman container?

BASH 

$ podman container run alpine

If you have never used the alpine container image on your computer, Podman probably printed a message that it couldn’t find the container image and had to download it. If you used the alpine container image before, the command will probably show no output. That’s because this particular container is designed for you to provide commands yourself. Try running this instead:

BASH 

$ podman container run alpine cat /etc/os-release

You should see the output of the cat /etc/os-release command, which prints out the version of Alpine Linux that this container is using and a few additional bits of information.

Challenge

Hello World, Part 2

Can you run a copy of the alpine container and make it print a “hello world” message?

Give it a try before checking the solution.

Use the same command as above, but with the echo command to print a message.

BASH 

$ podman container run alpine echo 'Hello World'

So here, we see another option – we can provide commands at the end of the podman container run command and they will execute inside the running container.

Running containers interactively

In all the examples above, Podman has started the container, run a command, and then immediately stopped the container. But what if we wanted to keep the container running so we could log into it and test drive more commands? The way to do this is by adding the interactive flags -i and -t (usually combined as -it) to the podman container run command and provide a shell (bash,sh, etc.) as our command. The alpine container image doesn’t include bash so we need to use sh.

BASH 

$ podman container run -it alpine sh
Callout

Technically…

Technically, the interactive flag is just -i – the extra -t (combined as -it above) is the “pseudo-TTY” option, a fancy term that means a text interface. This allows you to connect to a shell, like sh, using a command line. Since you usually want to have a command line when running interactively, it makes sense to use the two together.

Your prompt should change significantly to look like this:

BASH 

/ #

That’s because you’re now inside the running container! Try these commands:

  • pwd
  • ls
  • whoami
  • echo $PATH
  • cat /etc/os-release

All of these are being run from inside the running container, so you’ll get information about the container itself, instead of your computer. To finish using the container, type exit.

BASH 

/ # exit
Challenge

Practice Makes Perfect

Can you find out the version of Ubuntu installed on the ubuntu container image? (Hint: You can use the same command as used to find the version of alpine.)

Can you also find the apt-get program? What does it do? (Hint: try passing --help to almost any command will give you more information.)

Run an interactive ubuntu container – you can use podman image pull first, or just run it with this command:

BASH 

$ podman container run -it ubuntu sh

OR you can get the bash shell instead

BASH 

$ podman container run -it ubuntu bash

Then try, running these commands

BASH 

/# cat /etc/os-release
/# apt-get --help

Exit when you’re done.

BASH 

/# exit

Run a ubuntu container, first with a command to read out the Linux version:

BASH 

$ podman container run ubuntu cat /etc/os-release

Then run a container with a command to print out the apt-get help:

BASH 

$ podman container run ubuntu apt-get --help
Callout

Even More Options

There are many more options, besides -it that can be used with the podman container run command! A few of them will be covered in later episodes and we’ll share two more common ones here:

  • --rm: this option guarantees that any running container is completely removed from your computer after the container is stopped. Without this option, Podman actually keeps the “stopped” container around, which you’ll see in a later episode. Note that this option doesn’t impact the container images that you’ve pulled, just running instances of containers.

  • --name=: By default, Podman assigns a random name and ID number to each container instance that you run on your computer. If you want to be able to more easily refer to a specific running container, you can assign it a name using this option.

Conclusion

So far, we’ve seen how to download container images, use Podman to run commands inside running containers, and even how to explore a running container from the inside. Next, we’ll take a closer look at all the different kinds of container images that are out there.

Key Points
  • The podman image pull command downloads container images from the internet.
  • The podman image ls command lists Podman container images that are (now) on your computer.
  • The podman container run command creates running containers from container images and can run commands inside them.
  • When using the podman container run command, a container can run a default action (if it has one), a user specified action, or a shell to be used interactively.