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[Intro Music]

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Okay guys, so we have just created a

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very first container using a

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hello-world image. We have pulled

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it from a Remote Registry called

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Docker Hub and afterwards I have

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created container and this

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container has printed some text to

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the terminal. Also in this text

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you see suggestion to try another

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container with this command

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'docker run -it ubuntu bash'. And

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with this command we will be able

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to create another container using

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ubuntu image. But let's try it

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without option '-it', and 'bash'.

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Simply as we have tried with

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'docker run hello-world'. Let's now

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type 'docker run ubuntu', and that's

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it, and let's see what will happen. Let me

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clear terminal, 'Ctrl+K', and here

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let me type 'docker run ubuntu'.

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You see that we again we are not

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able to find the image 'ubuntu:

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latest' locally. And that's why we

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have started pull operation from

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Remote Registry Docker Hub and you

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see that we have pulled several

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times and you see here different

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IDs. Now, I will not explain you

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what it means. We will get back

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to it later on when I will

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explain you how Docker works under

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the hood. For now, you should

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understand that we have simply

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pulled image called ubuntu from a

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Remote Registry Docker Hub. Also

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you'll see sha256 Hash, same as we

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have seen for hello-world image, but

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of course hash itself is different

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here from the hash for hello-world

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image. Also, you see finally the

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image was downloaded, it's status is

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downloaded; but afterwards after we

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have executed basically 'docker run

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ubuntu' command, we have returned to

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terminal, it means that actually

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nothing happens. And we are not

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able to do something inside of the

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ubuntu container. But it was

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immediately terminated afterwards.

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Why? Because there was no command

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that was executed inside of this

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ubuntu container. And if there are

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no processes running inside of the

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container, Docker automatically

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terminates the container. And if I

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enter 'docker ps' now, you will see

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that there are no containers

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running. But I am able to observe

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history of the containers that were

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exited. For that you could use

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command 'docker ps' with option '-a'

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like so. And now I will see that

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there was container that was based

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on ubuntu image, and there was

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command, this one that was executed

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automatically, here is this

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command. But we have not performed

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anything inside of the bash, inside

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of the container. That's why

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container has decided that bash

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should exit, and it was exited,

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process was terminated. And

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afterwards, Docker has exited

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container as well. That's why here

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you see that the status of this

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container is 'Exited About a minute

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ago'. Also you see information about

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previous containers that we have

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created in the previous lecture.

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And we have used there hello-world

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images, here, and here. We have

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created basically two different

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containers, and you see that they

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were exited about an hour ago.

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Okay, that is the status of this

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container that we have tried to

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create using 'docker run' command.

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Also, if I will list now local

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images with command 'docker images',

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I should see here ubuntu image

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on the list. That means that if

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I'll try to create one more

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container using Uubuntu image, it

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will be created using the same

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image as you see here, there was no

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need to pull the same image from

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Docker Hub. Let's try that again.

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And let's try it with the same

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command as we have used before,

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'docker run ubuntu', and we see actually

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nothing. But again, under the hood,

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Docker has created a new container

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based on this image. There was no

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need again to pull it from Docker

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Hub, because we already have it

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here on the list. But afterwards

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container was again automatically

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terminated. Let's have a look at

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history of containers. 'docker ps

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-a', actually there is

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alternative command to 'docker ps',

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and this command is 'docker

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container ls', and if l type here

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'docker container ls -a', you'll

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see actually same result as with

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'docker ps -a', it brings us

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history of all containers that were

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created before. And again you see

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here one more container that was

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created using ubuntu image, and this

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container was exited a minute ago.

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Here below you see a second

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container with the same image

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ubuntu, but this one was exited 4

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minutes ago. It means that each

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time when you execute the command

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'docker run' and some image,

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Docker creates a new container

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based on specific image. But now

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you may ask me a question, how we

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are actually able to log in into

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that container, ubuntu

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container, and execute some commands

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inside of the Ubuntu operating

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system. Answer is pretty simple.

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Let me show you. 'docker run -

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it ubuntu'; let's press Enter and

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see what will happen. And now you

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see that I have basically entered

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bash shell inside of the Ubuntu

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container, and I have logged in

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automatically as a 'root' user, here

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you see that. And here is actually

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ID of this container that was just

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created. And now I am still inside

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of this container, and container is

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still running. Let me show you that it

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is still running. Let me open up a

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new tab here in terminal, and let's

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enter 'docker ps' command. Here you

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see image that was used, this ubuntu,

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and also you see here CONTAINER ID,

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and this ID is the same as you see

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here in this bash shell inside of

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the ubuntu container. And now

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actually, we are able to perform

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some operations inside of this

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container. For example, let's use

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ls command and list files inside of

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the ubuntu container. And here you

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see some set of folders. And for

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example, you are able to list the

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files inside of the 'bin' folder.

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Let's do that 'ls bin', and you'll see

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some set of executables that you

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are able to use inside of the

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ubuntu container. Again, please

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notice that this set of files and

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folders is completely isolated

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inside of this ubuntu container. It

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is not a set of files on my macOS

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computer where I am running Docker

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right now. Actually, let me show

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you that to prove that. Let me

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open up one more tab, and here

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let me 'ls', and you'll see actually a

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list of folders on this macOS

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computer. And also I'm able to list

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the actually files in '/bin'

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folder, and you'll see a set of

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executables on my macOS computer.

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And this set of executables is of

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course different from this set of

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executable files. That's how you're

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able to list the files inside of

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the container. And again, container

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is still running. You could verify

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that here, 'docker ps', and you see

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that there is container with ubuntu

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image that is up and running and it

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is 'Up 2 minutes'. And also you see

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here which command was executed '/bin

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/bash', it is bash shell, and we are

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actually located now in this bash

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shell. Okay, please notice that

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this container runs now full

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featured Ubuntu operating system

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and you could verify version of

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this operating system using 'cat

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/etc/os-release'.

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You see here version Ubuntu 18.04.4

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Long Term Support release.

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Also we could try something else.

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Let's try for example 'echo' command.

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Let me clear terminal; and type

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echo "Hello from Ubuntu

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container", Enter, and you'll see

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"Hello from Ubuntu container", here in

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this shell. Please notice that we

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are able to use this command

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because there is such executable

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inside of the bin folder. Let me

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list contents of the bin folder once

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again. And you'll see here 'echo' on

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the list. Let's try something else.

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Let's clear terminal, and type 'hostname'

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command; and you'll see here

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hostname of this container. It

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actually matches with this ID here

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on the list. Also, we're able to verify

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which IP address was assigned to

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this container using command 'hostname'

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-i', like so, and you'll see

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IP address 172.17.0.2 here in this

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output. Great. That's how you're

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able to perform some commands

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inside of the ubuntu container.

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Let's now type 'exit', and let's exit

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from this bash shell. 'exit', and we

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can return back to our terminal.

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Let's now list the containers that

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are currently running, 'docker ps', and

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you'll see empty output. Basically

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you're able to use alternative

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command to 'docker ps', 'docker

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container ls'; and you'll see same

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result. There are no containers

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currently running. But if I enter

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'docker ps -a', you'll see that

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our ubuntu container was exited 34

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seconds ago. Why it was exited?

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Answer is pretty simple. We have

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exited from bash shell inside of

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the container, and that terminated

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bash process inside of the

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container. And when there are no

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processes running inside of the

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container, Docker simply terminates

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such container. That's what actually

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happened here in this example.

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Great. Let's also clear

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terminal and let's have a look at

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the size of the image that was downloaded

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for ubuntu containers,

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'docker images', like so. And here

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you'll see size equal to 64.

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megabyte. It is of course much more

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larger than the size of the hello-

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world container that was simply

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less than two kilobytes in size.

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But this size is relatively small

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in comparison to let's say, Docker

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installation itself that was around

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two gigabytes for macOS or Windows

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computer. But this size is still

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large in the Docker world, because

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we have used here full featured

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Ubuntu operating system. And in the

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next example, I would like to

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demonstrate you how you're able to

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create the Linux container using

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smallest image possible. Let's try

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that next. Bye-Bye.

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[no audio]