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‫All right before we jump into images, let's talk about what this section is all about.

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‫First, we're going to discuss the basics of images and the concepts that you're going to need

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‫and what is actually in an image and, just as importantly, what isn't in one.

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‫Then we're going to talk a little bit about how to find images on the Internet and we'll actually go and look

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‫at some, dive into that whole process of finding good images and how to manage those images once we've

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‫downloaded them or created them on our own machines. Then we'll jump into the fun part of actually

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‫making our own images.

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‫So before we start playing with images and learning how to use them for containers, we probably want

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‫to step into what exactly is in an image and what isn't. The way I like to explain it is very simple.

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‫It's the application binaries and dependencies for your app and the metadata on how to run it.

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‫But if we went to the official definition, it would be "an image is an ordered collection of root filesystem

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‫changes and the corresponding execution parameters for use within a container runtime."

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‫But I like my version better.

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‫Inside this image, there's not actually a complete OS. There's no kernel. There's no kernel modules

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‫like drivers.

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‫It's really just the binaries that your application needs because the host provides the kernel.

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‫That's one of the distinct characteristics around containers that makes it different from a virtual

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‫machine; it's not booting up a full operating system.

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‫It's really just starting an application, and that image can be really small.

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‫It can be a single file.

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‫If you're, for instance, using Go, one of Go's features is that it can build a static binary and have

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‫a single file as your application.

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‫So you could do that. Or you could have a very big image that's actually using some distribution like

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‫Ubuntu with its own package manager built in, and where you've installed Apache, and PHP, and your source

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‫code, and all the added modules you need.

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‫You can have it multiple gigabytes.