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[Intro Music]

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All right, we have just made a note

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of two commands that we have used for

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launch of mysql and phpmyadmin

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containers, and we will get back to

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them a bit later. For now let's

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again create two busybox

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containers, and let's try to

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perform communication between them

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using hostnames or names of those

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containers. Let's do that. Let's

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launch first busybox container here,

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'docker run -it busybox'. Let me

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open up a new tab, and here will be

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another busybox container, 'docker

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run -it busybox', and let me

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verify which IP addresses were

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assigned to those containers,

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'hostname -i', actually those IP

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addresses are the same as were

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assigned before. But again, the

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reason for that is that there are

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no other containers currently

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running in our setup. If there were

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additional containers with IP

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addresses that are used here now,

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for example, this one, then another

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IP address will be assigned to

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those busybox containers like

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17.0.5, 17.0.6, and so on. Great. Let's

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check the IP address of this

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container, 'hostname -i'; and it

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has address 172.17.0.2. And if you

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type 'hostname' like so, you could

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get hostname of this container, of

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this server. Also, same here, 'hostname',

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and let's now try to ping this

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busybox server by using its 'hostname',

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this one. Let me copy this

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hostname from here, go to this

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busybox container, and use same ping

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command but paste now hostname

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instead of IP address. Let's press

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Enter, and I see answer, 'bad address';

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and that means that we are not able

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to connect to this busybox

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container using its hostname. Let

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me also show you something. Let's

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open up a new tab; and 'docker ps'

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here; and let's use 'docker inspect'

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command; and type here ID of, for

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example, this container '39'

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like so. And you'll see again

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IP address of this container, here

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it is. Gateway, default gateway that

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is same for both containers. And

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here above you will see also field

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called Aliases; and now it is set to

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null. Now let me show you how we are

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able to set custom alias for this

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container. Actually let's go back

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here, and let's exit from this

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container, and exit from this

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container as well. And now let me

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type 'docker run --help', and

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here in this output you should see

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one option called '-h', here it is

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somewhere above, '-h', and here

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you see description, it is

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'Container host name'. It means that

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using this option you are able to

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override the default hostname that

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will be assigned to specific

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container. Also you are able as you

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already know using option '--name',

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it is somewhere here, and 'n',

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yes, here it is, '--name',

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you are able to assign custom name

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to the container. Recap that by

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default Docker assigns randomly

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generated name to a container. And

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now let's try to use both options

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'--name', and '-h

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hostname', and assign custom names,

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hostname, and the container name to

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those busybox containers, and verify

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whether something will change and

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whether we will be able to connect

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ping one container from another

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using either container name

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or hostname on that. Let's do that.

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Let me clear terminal, and here will

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be busybox1, 'docker run -it',

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let's use first option

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'--name', here let's name it

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'busybox1'; and next let's use

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'-h' option, it stands for 'hostname', and

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here let's say I'll use hostname

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'busybox-one'. I have used

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different names in order to

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distinguish between hostname and

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the name of the container. And

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finally let's use the name of the

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image, it is 'busybox'. Let's press

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Enter, and now we are in sh shell,

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instead of this busybox1

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container; and if I'll enter our

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'hostname', I should see 'busybox-one';

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and if I'll enter 'hostname -i',

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'hostname -i', I should

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see IP address of this busybox1

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container. Let's do the same, and

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let's create in similar way second

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busybox2 container. Let's do that

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here. 'docker run -it --name',

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name will be busybox2,

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and hostname will be busybox-two,

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and here will be the

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name of the image busybox. Let's

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press Enter, and we are now in sh

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shell here in the second container.

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'hostname' will provide us hostname

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of the second container, 'busybox-

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two', and 'hostname -i' will

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provide us IP address of this

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container. Let's as before try to

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ping first busybox container

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using its IP address, this one in

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order to verify connection between

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those two containers. 'ping 172.17.0.2',

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I'll get response of course. But if

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I try to ping by hostname 'busybox

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-one', I'll get, bad address

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'busybox-one'. Same response I'll get

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if I try to ping by using name of

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this container. Its name is 'busybox1'.

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Let's do that, 'ping busybox1',

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like so; and again, bad address

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'busybox1'. If I will go to this

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last step, and enter here again,

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'docker ps'; and afterwards, enter

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'docker inspect'. 'docker inspect'; and

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here let's inspect busybox1

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container. By the way, notice here

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custom names that were assigned to

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those two containers. And that's

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because we have used '--name'

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option when we have started

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those two containers. And here

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let's inspect for example 'busybox1',

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'busybox1'. I could use

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either name or ID of the container.

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Let's press Enter. And I see IP

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address of this container. But

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Aliases is still set to null. If I

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will go to this first step, and try

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to perform same action as we

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tried on busybox2, for example,

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'ping busybox2', or

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'ping busybox-two', I'll get same

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response, bad address. And the

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reason for that is that by default

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in default bridge network you

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are not able to communicate between

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different containers using their

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names, or hostnames, that is the

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rule in Docker. I don't know

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whether it will change in the

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future or not. But at the moment,

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it is like this. Actually, if you

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want to perform communication

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between containers using their names,

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you need to create first custom

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bridge network, and then create

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containers inside of that custom

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bridge network. And let me next

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explain you how you're able to

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create custom network using the

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Docker, and create new containers

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inside of that custom network. I'll

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see you next. Bye-Bye.

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[no audio]