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[Intro Music]

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In the previous lecture, we have

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successfully created a new

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container based on hello-world

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image, and we have seen such output

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in the terminal. Now, let me

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explain you what actually happened

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under the hood; and why this

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container has printed this text to

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the terminal. Let me show you one

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more diagram with image example. I

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have told you that every image is

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simply a set of different 'FS'

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layers. In one of those layers,

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there are instructions, text

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instructions, which tells Docker

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what it needs to do when a new

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container is created based on a

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specific image. For example, let's

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have a look at this image. In this

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image, there are several FS layers.

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Base Image is Ubuntu. In the next

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layer, there is an Application

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that was installed in separate FS

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layer. And for example, there is

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WordPress application. And finally,

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there is additional FS layer with

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some text, with some command that

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tells what container needs to do

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when it is created. An example of

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the command in this particular

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image is, 'start wordpress process'.

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Of course, this command is in human

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words, but under the hood it will

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be different. But again, idea is

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that there is a specific command

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that tells what to do, which

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process to start when new container

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is created. And in this example,

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when we have started hello-world

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container, there was an instruction

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to run a specific executable file

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that prints text to the terminal.

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That's it. And I could actually

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quickly show you where is this file

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inside of the container. For that I

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could enter 'docker inspect' command.

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Actually, I need to enter 'docker ps

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-a' first in order to find out

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ID of the container. No worries, we

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will talk about ID a bit later. And

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next type, 'docker inspect'; and

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copy this ID from here like

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this. And let me scroll up a bit.

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And here you could find 'Cmd'

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instruction; and in this container

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'hello' file was executed. It is

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basically Linux executable file and

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it's goal, just simply print such

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text to the terminal. That's it.

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Alright, but what is container, and

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what you're able to do inside of

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the container? Let me answer this

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question in the next lecture. See you there.

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[no audio]