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So we've got this Dockerfile.

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How can we now turn this into an image

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and then into a container ultimately?

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Well, we need to open up the terminal

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and again here, I will simply use the terminal integrated

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into my IDE, which is the default system terminal though.

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And here, we can now run docker

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but not run but build

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because now I don't wanna run a image,

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at least not yet

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but first of all, I wanna create an image.

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I wanna create an image based

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on the instructions in this Dockerfile

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and that's what the build command does.

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It tells Docker to build a new custom image based

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on a Dockerfile.

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And here we now need to specify the path

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where Docker is able to find the Dockerfile

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and if we just type a dot here,

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we tell Docker that the Dockerfile

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will be in the same folder

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as we're running this command in.

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And since I'm using the integrated terminal,

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this is already navigated into this project folder.

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Hence the Dockerfile is in that folder.

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Hence, if I hit Enter,

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this now creates this image.

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And you see it executes a couple of steps here.

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It executes the FROM command to take the node image.

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Sets the working directory.

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Copies our code.

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Runs npm install.

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We can ignore the warnings here.

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Then exposes the port.

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And recognizes this command you could say.

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And at the end, it's done

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and it built an image with this name here,

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with this ID.

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Now, keep in mind, as mentioned in the first course module,

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on Windows, the output looks a bit differently.

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Here you find your image ID here.

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You can also assign custom names to images

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but for the moment, we can go with that.

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So copy the ID that was generated

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and then you can run docker run and use that ID here.

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And if you hit Enter,

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this will now start this container

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and you will see it doesn't finish,

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it keeps on running.

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The reason for that is that the command we executed here

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starts a Node server,

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which is also an ongoing process that doesn't finish.

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And therefore, the container also keeps on running

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because the command that was executed

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when the container is started

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is a command that doesn't finish.

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And hence, the container keeps on going.

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But you will notice

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that if you visit localhost,

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you won't see the website,

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even though we exposed the port here

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in our Dockerfile.

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So why is that not working

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and what can we do here?

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Well, are almost here.

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First of all, let's shut this container down

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because clearly, it's not working as intended.

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To do that, you can open up a new terminal

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and there run docker ps

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to see all the processes.

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And if you just run docker ps,

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without -a, you see only the running processes.

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And here we see one container based

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on this image we created.

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And it's still up and running here

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because as I said, it doesn't quit automatically.

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Now, we can stop this container manually

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by running docker stop

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and then using the container name,

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which was automatically assigned here.

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If I now hit Enter,

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this takes a short while

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and it will shut down this container

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and therefore also the Node server running inside

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of the container.

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Once this is finished,

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if you run docket ps again,

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you see no running container anymore.

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Instead now you would have to enter ps -a

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to see your container there.

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It now exited.

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Okay, so now we shut this down.

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What went wrong though?

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Why were we not able to listen

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on port 80 for this custom container?

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Because one step is missing here.

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Yes, we have this EXPOSE 80 instruction in our Dockerfile

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but actually, this instruction only is added

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for documentation purposes.

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It doesn't really do anything.

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It is a best practice to add it

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and you should add it to clearly document

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which ports will be exposed by your container

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but you need to do more.

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You could actually also remove this EXPOSE 80 instruction

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and still do what I'm about to show you

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and it would still work.

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So this instruction is really 100% optional,

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yet as mentioned, recommended that you add it.

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But what really maters is that when you run the container

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with docker run that you then add a special option.

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So therefore, what we need to do

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is we need to run this container

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but we need to add a extra flag here

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and that's the -p flag in front of the image name,

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which stands for publish.

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And this allows us to tell Docker

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under which local port,

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so under which port on our machine here

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this internal Docker container-specific port

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should be accessible.

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And the syntax here is as follows.

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You have -p

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and then you specify your local port

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under which you wanna access this application.

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In this case, for example, 3000.

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This is up to you.

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And then colon

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and then the internal Docker container exposed port.

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In this case, 80,

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since we're exposing 80 in this container.

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And with this now if we hit Enter,

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this again starts

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but now if I reload localhost:3000,

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I see my application and I can Learn Docker in-depth

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because now this is published

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under the local port 3000.

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And this is now our first custom image based

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on the default Node image

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with our own instructions

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and our own Node app.

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And I'm pretty sure that it at this point,

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there still are many question marks in your mind

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and in your eyes

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and I will get to all of them

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but I hope this general idea here is clear.

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That we have a custom image based

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on a existing image,

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the node image, where we then have a couple of instructions.

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For example, to copy our code

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and install all dependencies.

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And then, we create this image

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with the docker build command

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and we then run a container based on that created image

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with the docker run command.

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And then here again,

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this container is still up and running.

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If we wanna close it,

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if we wanna stop it,

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we again have to first of all, find the container name

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with docker ps here.

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And then we can run docker stop container name.

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And of course, there are also ways

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of assigning your own names

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and so on and we'll get to these ways

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and these features as well

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but for now, these are the basics you should be aware of.

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How to build your own image,

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how to run that image as a container,

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how to stop that container

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and most importantly,

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you should understand how these core concepts work together.