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This video is about container runtimes.

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The container runtime is the software that runs a container.

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And common container runtimes are ContainerD and Cryo.

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You write C-R-I-O, but Cryo is the way to pronounce it.

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The container runtime is a part of the container engine.

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And the container engine is a complete software solution that is used to start

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and manage the container.

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Docker and Popman are the most common container engines.

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There are some small other ones around as well.

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Docker started the container revolution in the year 2013-2014.

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And Docker has been the dominant container engine until the release of

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Red Hat Enterprise Linux 8 in 2018.

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And that is because Red Hat didn't want to be depending on the Docker development.

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Red Hat wanted something themselves.

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And that is why with the release of RHEL 8,

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Red Hat offered Popman as a replacement for Docker.

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And it dropped support for Docker.

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And in case you are wondering,

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wasn't that problematic for current Red Hat Docker users?

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No, because container images are standardized in the Open Containers Initiative.

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And if you just replace Docker with Popman, it would work.

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Also, because Popman is using a CLI experience that's completely similar to the Docker CLI,

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Popman is now commonly available and used in all the distributions as an alternative for Docker.

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Now, let me tell you how you can use Docker on Ubuntu.

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If you want to use Docker on Ubuntu, you need to install it.

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That's pretty easy.

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Just use sudo apt install docker.io.

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Popman on Red Hat does not need any further installation,

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because it's part of the default installation of most Red Hat and Red Hat family installation patterns.

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Only on minimal installations, you may have to use dnf install popman to get your hands on it.

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Let me show you how to install Docker on Ubuntu.

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So how do we install Docker?

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Well, simple, sudo apt install docker.io.

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And that should be doing it.

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So how about a first test drive Docker run nginx?

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Oh no, permission denied.

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You know what is going on?

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In order to run Docker, the user who wants to run Docker needs to be a member of the Docker group.

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So I'm going to use sudo usermod minus a uppercase G docker for student, which is my local account.

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Next, the problematic thing is that I would need to log out and log in again.

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But that's a little trick when I use new grp docker and I use id again.

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Now you can see that I'm a member of the group Docker.

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And as a result, I should be able to use Docker run minus d nginx.

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Minus d is running it in detached mode.

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And there we can see that I'm running it in detached mode.

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Minus d is running it in detached mode.

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And there we can see that it is unable to find the image locally.

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It is running the image and it just did.

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So we have Docker up and running.

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Oh, and don't try to install Docker on Red Hat and family.

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Because on Red Hat and family, it's really not supported.

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And it will break with every single software update you do.

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On Red Hat and family, Podman is the alternative.

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And the good news is that Podman has the exact same command line experience as Docker.

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All the arguments are the same.

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So instead of Docker run minus d nginx, you would use Podman run minus d nginx.

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More about this in the next couple of videos.