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In the last section we broke down the contents of our Docker file and got an understanding of the overall

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contents or structure of it.

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We now know that there's a handful of instructions that we can use to customize how our image is built.

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These are three of the most important instructions to know and we'll introduce a handful of other ones

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over time.

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In this section I now want to kind of break down what was really occurring behind the scenes with each

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of these instructions.

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We're going to first begin by taking a look at a little analogy.

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So this is going to be an analogy to help you understand the structure or purpose of those lines of

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configuration inside that darker file so quick analogy I can tell you writing a doctor file is a little

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bit just like being given a computer.

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So a brand new computer with no operating system on it and being told to install google chrome on there.

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So I want you to imagine what you would do if I handed you a computer that has no operating system on

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it.

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And I told you you have to install google chrome on here but here is probably what you would end up

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doing.

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The first thing you might do is try turning on that laptop or turning on that desktop.

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And when you turned it on you would probably maybe see some boot up process but then you would eventually

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be given a message that says something like hey sorry no beautiful drive or no operating system.

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I'm just an empty computer.

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I don't know what to do.

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So the first thing you would probably do is install an operating system you need an operating system

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on that computer in order to go through all these sequential steps on here.

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If you want to download Google Chrome you have to go and download it from somewhere by opening up your

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Web browser and you have to navigate to Chrome Doug Google dot com.

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You have to download the installer and open a file explorer and then execute that installer.

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So those series of steps right there those are all steps that are facilitated by the installation of

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that initial operating system.

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If you didn't have an operating system there would be no default browser to start up.

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You would not have a file or folder explorer to startup and you probably would not have any way to run

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an executable file.

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All of these steps are kind of preceded or dependent upon having an initial operating system so then

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going through all those initial steps eventually you would be able to execute the chrome executable

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and start up that browser.

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So these steps right here very similar to what we just did inside that darker file when we specified

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that base image of Alpine.

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That was a lot like installing an initial operating system by default when we create a container or

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me when we create an image.

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We have an empty image.

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There's really nothing inside there.

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No infrastructure no programs that we can use to navigate around a file or folder system.

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There's nothing we can use to download or install or configure dependencies.

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There's nothing in there.

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So the purpose of a specifying a base image is to kind of give us an initial starting point or an initial

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set of programs that we can use to further customize our image.

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So that is the purpose of that first line from Alpine.

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We said that we wanted to use the Alpine Docker image as kind of an initial operating system or a starting

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point for the image that we are creating.

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Now your very initial follow up question might be well why did we use Alpine.

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What is Alpine.

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So that's a good question.

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Another brief aside why did we use Alpine as a base image.

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Well back to you.

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I'm going to kind of pose a question I'm going to say to you why do you use Windows or Mac OS or Ubuntu

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or some other Linux distribution on your personal computer.

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The answer is that you use any particular operating system because it kind of suits your needs.

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Windows might have a program that you need to use your computer effectively you might use Mac OS because

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it has a built in terminal and that's really nice for you.

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In other words you use one of these default operating systems because it has a set of prenatal programs

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that is useful to you and what you are trying to accomplish.

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So we just made use of Alpine as a base image as kind of like an operating system of sorts because it

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includes a default set of programs that are very useful for what you and I are trying to accomplish.

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We are trying to install and run reds and the Alpine based image has a set of programs inside of it

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that are very useful for installing and running red is the command that was or the program that was

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most useful for you and I for installing and running gratis was found on the second line of the docker

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file.

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We had said run a P.K. ad update read this.

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This is not a docker command right here.

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This line has nothing to do with Docker whatsoever.

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AP K is a program called Apache package something I think it is a package manager that comes pre installed

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on the Alpine image and we can use that package manager that is built into alpine to automatically download

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and install it read it for us.

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So we made use of Alpine because it had this package manager program automatically included inside of

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it.

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And so it made it a very convenient thing to start with inside of our Docker file.

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All right.

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So I think we got a better idea of what's going on with this Frontline and I think we've got kind of

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a reasonable idea of at least the right hand side of this one.

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You know the actual like Commander line of code that was executed but we still need to have a better

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understanding of what run over here is doing have a better understand standing of what command is doing

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and kind of put this entire equation together.

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So quick break and come back an section and do a little bit more of a deep dive.

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So I'll see you in just a minute.