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- So in this video I will tell
you about container images.

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The purpose of a container
is to start an application.

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And a container image contains

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all of the dependencies that are required

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to start that application.

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Existing container images can
be used to run containers,

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and images are provided through public

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as well as private image registries.

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Docker Hub, accessible at hub.docker.com,

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is the biggest public registry

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and the most commonly
used registry as well.

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Let's check out Docker
Hub before continuing.

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So this is hub.docker.com.

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You can create an account

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which offers a couple of benefits.

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If you are looking for a specific image

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you can also search for
the image right here.

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So let's look for nginx, for instance.

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And what do we see?
We see verified content.

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Verified content are reliable images

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which has been verified

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and there is normally some company behind.

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There's also community images.

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And the community images,
well, if you see 10,000,

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that means 10,000 or more.

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Let's have a look at the verified content.

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So here we can see the Docker image,

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including the command to fetch the image

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and a quick reference.

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So normally the image
has some documentation

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associated to it as well.

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And in some cases, this
documentation is really very useful.

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Here you can see that the
documentation is very detailed

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and is really helpful in
running the nginx container,

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that's not always the case.

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If you're ever looking for images,

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have a look at the Docker website.

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It's the best way to find your images

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and much more convenient
than a command line.

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So while running containers,
the required images

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are fetched automatically
and stored locally.

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And to find images you can
use the search features

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on the image registry

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or the docker or podman search command.

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And to fetch an image, you
can either run the container,

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which will automatically fetch it,

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or use docker or podman
pull to pull the image

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without running it as a container.

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After pulling some images

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you can use docker or podman images

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which will show images currently installed

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and available for the current user.

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Let me show you.

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So for this podman demo I'm
going to leave my root shell

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because we don't need root
privileges to run containers.

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And running containers from a root shell

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is not the best practice that's available.

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Now this is centos and on centos

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podman is installed by default,

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that makes it very easy.

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So if I use podman search nginx

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then it's going to search
in the default registries

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and it is showing all the registries

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where it has found the image.

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Now, in podman, multiple
registries are pre-configured.

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If you are using Docker,

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docker is by default
going to the Docker Hub

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and you will just see the image name.

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Now what we see here is the nginx image

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that we have just seen
in the webpage as well,

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and if I want to fetch it,
well, I can use podman pull.

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Now, podman pull can be fo
followed by a short image name

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but the nicer way of doing it

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is the fully qualified image name,

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so podman pull docker.io/library/nginx.

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Why the fully qualified image name?

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Well, because there's more
than just the Docker registry

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and this allows you to identify

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exactly which image you want to use.

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Here we can see the image being pulled,

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the multiple layers of the image.

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That's because this nginx
is probably based on some

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other container images that
are managed by somebody else,

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and all of these layers
are managed independently.

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Now, I can use my podman images command

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and the podman images command is showing

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the image available on the system

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with the size of 146 megabytes.

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There's no real needs to do podman pull

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before actually you're
running your container,

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but I wanted to show you

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a little bit about managing images.

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Now that you know how to work with images

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let's learn about learning containers.