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[Intro Music]

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Before creation of multiple

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containers based in the same image,

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let me briefly explain you what

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option '-t' means in 'docker run'

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command. Basically, in one of the

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previous lectures in multiple

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actually, we have used this option,

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but I have not yet explained you what

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it means. Let me first type here,

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'docker run --help'; and here

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you'll see this option on the list.

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You could use either '-t' or

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'--tty'; and it

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allocates a pseudo-TTY. I'll explain you

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what it does actually in a minute.

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Also, if you scroll up, you'll find

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option '-i' or '--interactive';

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and with this option

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in place, you will be connected to

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'STDIN', standard input, or a

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specific process that is running

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inside of the container. Okay.

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Let's first create container using

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only '-i' option. Next, let's

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try to use only the '-t' option.

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And finally, let's combine '-i'

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and '-t' options together.

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Okay, let's do that. 'docker run

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-i alpine'; and here I am now

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attached to 'sh' process inside

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of the alpine container; and I'm

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able to list files, I'm able to

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create new folders, 'mkdir test', 'cd

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test'. Next, let's for example, write

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some text to the file like, 'echo

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'Hello from Alpine'; and let's

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write this text to 'file.txt'.

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Let's now list the files in the

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'test' folder, and we see response

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from the process and you see file

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name file.txt. And now let's

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read the contents of this file, 'cat

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file.txt', and I should see 'Hello

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from Alpine'. And yes, I see this

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result. But as you see here, when

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we use only '-i' option, we don't

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see any command prompt, we don't see

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any formatting of the output and so

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on. That's why with option '-t'

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Docker is able to create for

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you, pseudo-TTY; and it will

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actually produce some nice looking

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command prompt, format results,

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and so on. Let's try that. I could

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try to terminate this process using

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Ctrl+C, but it will not work. And

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you know why is that, because this

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process, 'sh' process inside of this

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container does not accept such

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commands. That's why you are able

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either to stop container, or kill it, or

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you are able to use 'exit' command

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inside of this 'sh' terminal that

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will exit from 'sh' process. And of

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course container will be terminated

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after that. Let's try that, 'exit'.

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And yes, we were exited from 'sh'

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process and if I list

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containers now, 'docker ps', I will see

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empty output, there are no

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containers currently running. Now,

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let's try to create same container

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based on alpine image, but now using

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only '-t' option. Let's do so.

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Let's clear terminal, 'docker run

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-t alpine',

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[no audio]

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and I actually see command prompt,

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but I am not able to enter any

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commands, and they don't get any

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results from it. That's because

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now I'm not actually connected to

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standard in of 'sh' process. That's

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why it's not enough to use only

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'-t' option that will

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emulate pseudo-TTY. You will not be

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able to enter any commands, or get

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any output from specific process.

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Let me exit from this. Actually I'm

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not sure whether I will be able to

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do so. No, I'm not able to do so.

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That's why in this case I need to

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terminate container manually. Let's go

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to separate tab, 'docker ps' here, and

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'docker kill', and ID of the container.

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Container was killed and I see

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that this first session, this step

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'just rang a bell!'. It's funny. Let's go

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here, and I see that this process

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was terminated. Okay. Let's now

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launch same container with alpine

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image but now using both options

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'-t' and '-i'. Let's clear

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terminal, 'docker run', and you are

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able to use those two options

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'-i' and '-t' separately like so;

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or you're able to combine them and

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write simply '-it'. Please

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remember that now we are using two

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different options, not single option

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called 'it'. Great. Let's now type

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name of the image 'alpine', and press

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Enter. And now you see command

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prompt. And if I'll 'cd' for example to

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'bin', you'll see that this command

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prompt will be adjusted

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accordingly. If I list files here

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in 'bin' folder, you will see that

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they were formatted with different

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colors and that's thanks to pseudo

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TTY. Great. That's how you're able

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to get access to specific process

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using pseudo-TTY, and 'interactive' option.

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That will actually connect you

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to standard input and standard

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output of specific process. In our

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case, that was default process 'sh'

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shell. Great. Let's now try to

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terminate this process using Ctrl+

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C, but it will not work. Reason is

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the same as before. I have

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explained you that 'sh' process does

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not accept any system commands, but

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you're able to exit from this

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process as from any shell using

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'exit' command. Let's type 'exit'. This

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'sh' process inside of the container

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will be terminated. There will be no

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other processes running, and Docker

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will therefore terminate this

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container. Let's type 'exit', Enter, and

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we get back to our terminal

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prompt and if I'll list containers

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now, 'docker ps', you will see nothing.

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Container was exited. Great. That

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is the difference between '-i',

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'-t', and '-i -t' options.

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Let's now try to do the same with

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for example ubuntu image. Let's

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clear terminal, and type 'docker run

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-it ubuntu. Recap that ubuntu is

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already present in our local images

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cache. Container was created, and we

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were logged in as root user. And

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recap the in Ubuntu default command

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is actually '/bin/bash'. Let me

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list containers now. And here

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you see this command, '/bin/bash'. This

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is actually shell but it differs

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from this 'sh' shell. That's why here

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in this step, you'll see another

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command prompt and it includes user

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name and host name of this ubuntu

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container. If I list files, I will

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get a similar result and if I'll

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'cd' for example to 'bin', list files

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here, I get similar output same as I

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have seen in 'sh' shell. Let's also

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try to terminate this process using

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Ctrl+C, also same result, but you

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are able again to exit from this

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process, in this case 'bash' process

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using 'exit' command. And now process

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was terminated, and container was

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deleted as well. Let's verify that,

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'docker ps', and now there are no

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containers currently running. That's

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all about '-t' option that

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you could use with 'docker run'

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command. And in most cases it is

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used along with '-i' option. And those

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options could be combined and you

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could write simply '-it'. '-t'

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option creates pseudo-TTY that

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allows you to interact with

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specific process inside of the

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container. That's all for this

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lecture. And in the next one let

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me create multiple containers based

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on the same image. I'll see you

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next. Bye-Bye.

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[no audio]