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In the previous lecture, we have successfully created a new container based on Hello world image and

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we have seen such output in the terminal.

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Now let me explain you what actually happened under the hood and why this container has printed this

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text to the terminal.

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Let me show you one more diagram with image example.

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I have told you that every image is simply a set of different layers.

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In one of those layers there are instructions.

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Text instructions which tell Docker what it needs to do when new container is created based on specific

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image.

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For example, let's have a look at this image.

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In this image, there are several layers.

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Base image is Ubuntu.

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In the next layer there is an application that was installed in separate layer and for example there

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is WordPress application.

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And finally, there is an additional layer with some text, with some command that tells what container

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needs to do when it is created.

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And example of the command in this particular image is start WordPress process.

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Of course, this command is in human words, but under the hood it will be different.

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But again, idea is that there is a specific command that tells what to do, which process to start

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when new container is created.

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And in this example when we have started Hello world container, there is an instruction to run specific

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executable file that prints text to the terminal.

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That's it.

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And I could actually quickly show you where is this file inside of the container.

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For that I could enter Docker inspect command.

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Actually, I need to enter Docker dash first in order to find out ID of the container.

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No worries.

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We will talk about it a bit later.

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And next type docker inspect and copy this id from here.

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Like this.

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And let me scroll up a bit.

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And here you could find cmd instruction.

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And in this container Hello file was executed.

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It is basically Linux executable file and this goal just simply print such text to the terminal.

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That's it.

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All right.

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But what is container and what you are able to do inside of the container?

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Let me answer this question in the next lecture.

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See you there.