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[Intro Music]

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Before going on, I need to perform

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some cleanup of my Docker setup

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because I have some cached images

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and some containers that were

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stopped. If you have clean Docker

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setup feel free to skip this

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lecture and move on to next one.

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All right, let me list

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containers here that were stopped

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'docker ps -a', and here I see

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bunch of stopped containers. And in

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order to remove all stopped

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containers, I could use command

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'docker container prune'. There is no

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short version of this command,

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that's why I'm using Container

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Management Command along with 'prune'

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sub command. Type 'Y' here, and all

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stopped containers were deleted.

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And now if I list containers using

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same command 'docker ps -a', I

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will not see any containers on the

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list. Great. Let me now list all

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images that I have before pulled

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from Docker Hub. For that I could

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use short command 'docker images',

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and here is a long list of images

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that I have used before in the

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previous long practice chapter. And

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I see such images as mysql,

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wordpress, httpd, redis, and so on.

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At the moment, those images are not

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used, and there are no containers

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created from those images, that's

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why I'm able to safely prune those

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images. And for that I could use

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'docker image prune' command. Let me

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first list all commands, sub

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commands of Docker Image Management

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Commands, 'docker image --help';

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and here is this list of sub

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commands that you are able to use

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along with image management

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command. And here is 'prune'

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command. And with help of this

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command, you are able to remove

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unused images. Image is

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considered unused when there are

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no running or stopped containers

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that were created from this image.

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Great. Let me know list all

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possible options for 'prune' command,

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'docker image prune --help',

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and here are some options.

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And notice that with '-a' option,

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or '--all', this long

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version of this short command, you

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are able to, Remove all unused

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images not just dangling ones. It

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means that just with 'docker image

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prune' command, Docker will remove

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all the so called dangling images.

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An image is considered dangling

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when there is no corresponding

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version of this image at Docker

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Hub. For example, when you have

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pulled a specific image from Docker

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Hub, but afterwards, such image was

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removed from Docker Hub, but it

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remains in your local cache, this

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image is called dangling image. But

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I want to remove all unused images,

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and that's why I need to add '-a'

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option to 'docker image prune'

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command. Let's do that, 'docker image

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prune -a'. Yes. Notice that

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this will remove all images without

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at least one container associated

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to them. At the moment, I don't

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have any containers running or

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stopped. Right, let's press enter

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here. I need to cut out because

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Docker is removing several

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gigabytes of images. And finally,

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images were deleted. And in this

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output, I see a long list of logs,

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like deleted: sha256, and then

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comes the list of hexadecimal

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characters. And here in this

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output, I see a long list of

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such logs. Also, I see such logs

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as 'untagged: node: latest' or 'untagged:

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node@sha256', and then

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comes again SHA Hash. And again,

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this list is much longer than the

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amount of images I have used on

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this Docker machine. And the reason

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for that is that basically every

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image consists of multiple file

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system layers. And that's why

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Docker has removed corresponding

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file system layers instead of just

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removing images. That's why in this

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log output I see multiple lines,

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because every image may have

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multiple FS layers. For example,

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this busybox image had two layers,

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that's why here I see those two

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deleted lines. alpine image has

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only one, that's why here I see only

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this one deleted line. But no

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worries, we will talk about all

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those details a bit later. For now

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you need to understand that I have

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successfully deleted all images

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that were stored in my local cache.

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And now if I enter 'docker images'

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command, I will see nothing. There

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are no images in my local cache and

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we are able to go on. Next I will

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start from scratch and download

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very first, most simple hello-world

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container, and explain you

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what happens under the hood and

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what is the structure of that image

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that we will download. I will see

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you in the next lecture. Bye-Bye.

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[no audio]