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  • Today we're going to talk about Docker.

  • For a couple different reasons, one of them being that Docker and containerization, in

  • general, are becoming more and more prevalent in the architectures that people are working

  • in in AWS or if you ship something to Digital Ocean.

  • They are just very important to be able to do this, but it's also incredibly important

  • in our development environments, and as I go through tutorials in the future I want

  • to be able to use Docker images in order to ship code as a starting point for some of

  • the applications and projects that we're going to look into.

  • I'm going to take this standpoint working from a mac, we're going to go from start to

  • finish with install Docker and working with Docker images that already exist, to creating

  • Docker containers, and understanding what it's like for us to create our own images

  • and then share those with the public.

  • We're going to get started using Docker for Mac, which is a new application that can be

  • installed into the /Applications directory, and there is also an equivalent version for

  • Windows.

  • If you're working on Linux, you don't actually have to worry about either of these things

  • because Linux can support it natively.

  • So for this I already have Docker for Mac downloaded.

  • I'm going to move over here and just install this.

  • In order to do this I had to uninstall everything that I had on my system so that we could make

  • this as thorough and realistic as possible.

  • So just drag and drop.

  • Now we're going to run Docker for Mac... there it is.

  • So you do have to allow this to use some network privileges, so you have to be an admin user

  • or a sudoer to be able to do this, but it's going to get you set up pretty fast.

  • So it goes on and does it's own thing here, but this will give us a couple different tools.

  • We'll just watch this.

  • So it is currently running.

  • This will give us Docker the command line utility, it's going to run Docker the server

  • for us and then it's going to create a VM that's actually running the Docker server

  • on, and from there it will also give us Docker Compose, which is an orchestration tool that

  • I'm not going to get into at all today, but I will in future videos just because it's

  • so useful from a development standpoint.

  • So, if I type "docker" it gave us this utility.

  • If I run "docker" and look at the version, this is the newest version that came out, as of

  • the time of recording this, just a few days ago.

  • If we look at the containers that are running, we don't actually have anything running, and

  • that's because we didn't tell it to run anything, but we also don't have any images yet.

  • If we look at Docker images you'll see that we have none here.

  • The first thing that you're going to do when working with Docker is you're going to have

  • to start a base image to work off of.

  • For us we're going to just pretend that we're just working with ubuntu.

  • For that we're going to need to run "docker pull ubuntu" and wait for it to download.

  • Before we move too much further on, we should talk about a few of the terms that are going

  • to be thrown around as we deal with more and more Docker.

  • The first one is "images".

  • Images are prepackaged bundles of changes that you've made to a file system, so image

  • that you start with ubuntu in this case which is just going to be the bare bones operating

  • system, and then if we wanted to build something more we would apply changes to it that that

  • we install something new or make a configuration change and that would become a different image

  • by stacking layers.

  • And then from there we'll get into probably the most important thing that we deal with,

  • and that's "containers", and that's actually when you take the image and you run it, and

  • you make use of that container.

  • So for us we'll do that right now.

  • We can do that by doing "docker run" and we'll pass it a few flags to make it interactive,

  • and then we'll give it the command, so we give it the image and the command name, and

  • this will go and run bash inide of an ubuntu thing.

  • So that we can make sure that we're not running on our mac by typing 'uname' and you can see

  • that we're running on Linux.

  • The first thing that we're going to do here is we're going to make a change and see what

  • happens.

  • I'm going to echo "STuff" into Test.txt and then just make sure it's there.

  • Yep, it's right there, right at the beginning.

  • So we'll exit this, and we'll run "docker ps".

  • There are no containers running.

  • Which I didn't actually show you what a container looks like when it is running, but we'll go

  • back into ubuntu and see if we can take a look at what's going on here.

  • So if we run this again and we run "ls" you'll notice that the Test.txt that we had up here

  • is not here, and that is because every time you create a container or you run and image

  • you create something that is entirely new, it is whatever the starting point was for

  • that image, but everything that happens while it's running is ephemoral, or it doesn't matter,

  • it just kind of keeps on churning.

  • There are ways to get around that by sharing some volumes or connecting some network things

  • together, but that's a little bit more complicated and we'll get into that when we talk about

  • docker-compose.

  • If I split this right now and I run "docker ps" you'll see that we do have a container

  • running.

  • Oh this is really ugly to look at though isn't it?

  • So we'll slide this over for a second.

  • And this gives us our container ID, the image that we used, the command that it's running,

  • and how old it is.

  • It also gives it a name, which if you don't provide a name for it, it comes up with some

  • pretty comical names.

  • So this is a "cranky turing".

  • So if we separate this back out.

  • We know that since we ran this container from an image that it always starts at the same

  • spot, regardless of how many times we run a container using the exact same image.

  • From here we're going to transition into something a little bit different, and that is containers

  • are cool and images are cool, but what happens if we want to make our own image.

  • So, imagine that we want to ship somebody ubuntu and we want it to come pre-installed

  • with some things.

  • So, in my particular case, I want to make sure that "wget" is there so that it's easy

  • to install things, and if we run our ubuntu image and we run "wget" you'll see that "oh

  • it's not there".

  • So that's kind of a bummer.

  • There's a really neat way of doing this in Docker and that is through what's known as

  • a Dockerfile.

  • And then from here the Dockerfile is a way to specify the recipe essentially, the steps

  • that we're going to take in order to take an image that already exists, in this case

  • "ubuntu", and turn it into something that more fits our needs, which in this case is

  • that we need ubuntu with wget and we need it to always be there.

  • So for that I'm going to open up Atom, I'm going to create a Dockerfile.

  • The Dockerfile has a slightly different syntax than a normal programming language because

  • its more just a series of steps, kind of like a script except you don't have the same power

  • of calculation that you would have if you were writing something like a ruby or a bash

  • script.

  • You have to follow a certain structure.

  • So the first thing that you have to do when creating a Dockerfile is that you have to

  • say what it's coming from, this is the starting image, or the layer that you're going to begin

  • with.

  • For us we're going to start with Ubuntu, and then from here we need to run some things.

  • Everything that comes after "RUN" is going to be processed inside, and then like I was

  • kind of saying earlier if you install something new, that creates a new layer.

  • Each of these command will create something, a different layer on top of of this.

  • And our image will actually be the final layer that is created because it was built up of

  • all the layers that existed before it.

  • For us we're going to "apt-get update" and then pass it a few flags to make it a little

  • quiet, and the we will also say "apt-get install wget" and we'll pass this just to make it

  • a little quiet too.

  • From here the other thing that you need to have is what is actually going to happen when

  • you run an image, and that is by default you can actually do "docker run ubuntu" and it

  • will go off an run something.

  • I actually don't remember off hand what ubuntu does when you run it by itself, but you can

  • define a default command so that if it's something that's going to, say you have an image that's

  • going to go and process some data and then close, you can just type "docker run my_data_processor_image"

  • and then it will go off, do it's thing, and then just the process itself will die and

  • the container will go away.

  • So we don't have to do that, but in our case I want to because I don't want to have to

  • type "bash" every single time.

  • I'm going to put this in here to where it's just going to run "bash" whenever we do this.

  • We're going to save it.

  • We're going to bounce back over to our terminal sothat we can build this.

  • Behind the scenes I moved us into a different directory, but what you're going to do here

  • is type "docker build", we're going to name our image, in this case it's called "tagging",

  • but we're going to tag it as "wget" and then we're going to say build with the current

  • context, which just means use this directory and look for the Dockerfile that's here.

  • So it's going to go off and figure everything that it needs and then you'll see that these

  • are the steps that it takes.

  • Our first step was to say from this, this represents the layer that is "ubuntu", and

  • then our next step here is run "apt-get update" and also install wget.

  • It will show you everything that it's installing.

  • And then when it's finished, you'll see that it gives you this.

  • So it created an image here, and then you're going to come down here and this next step,

  • yet another layer that we're going to be adding to this is to say that you're going to run

  • "bash" as your default thing.

  • So now if we run "docker images" you can see that we have multiple images here, that is

  • the successful build of the image that we just made for "wget", and then we have the

  • ubuntu one which gives you this original SHA too.

  • The neat thing here is that you can also see the difference in what we did, us running

  • "apt-get update" and "apt-get install" on wget actually installed an extra 46MB worth

  • of space.

  • Let's run our image and see the fruits of our labor here.

  • So if we "docker run -it" and just type "wget", remember that we told it the command it should

  • run is bash.

  • So it should open us right into bash.

  • And we're going to "wget google.com" and it should just work.

  • There you go, so we went and we downloaded the index.html from google.com with the tool

  • that we installed and now everytime we want to work with something that needs "wget" we

  • can run our own image instead of working with the ubuntu image that didn't have that package

  • installed to begin with.

  • So the last thing that I said we were going to do in this short tutorial is that we're

  • going to take our image and we're going to put it on the web so that other people can

  • access it, but I'm also going to show you how to find other images that you can work

  • with.

  • So if we go back to the web browser, if you go to hub.docker.com you can see all of the

  • other images that exist out here.

  • This is looking at my profile page, but if we go to the dashboard here, well "explore",

  • you'll see that there are a bunch of different "official repositories", so Nginx is one for

  • instance that if you just type "docker pull nginx" it will pull this exact image.

  • Normally, you have to work off of things by username and then image name, but ubuntu for

  • instance, this is the exact image that we were using for our purposes before we installed

  • wget on top of it.

  • There are many of these things, so there are a lot of different things that you need necessarily,

  • or that you might want to work with, like say you want to play around with node, but

  • you don't want to install it on your local machine, you can pull the official node image

  • and then you can go into the container that it starts and run bash in there for instance

  • to give youself a shell so that you can work with node directly.

  • Wordpress for instance, you just spin up a container that is already running wordpress

  • and go from there.

  • If we look back at the dashboard, I have a couple just random projects that I've sort

  • of worked with, but this one, the "elixir-ide" is me experimenting and putting an ubuntu

  • image out there that had everything that I needed for working with elixir, so I put a

  • text editor in there that I wanted to use, and then pre-installed syntax highlighting,

  • and pre-installed elixir for it so that I could just spin this up if I ever want to

  • do any and I didn't have to have elixir installed on my machine.

  • We need to push some things up here, and I'll show you how to do that.

  • So if we "docker push wget", you'll see that we... oh I'm actually inside of the container

  • that's why I'm so confused.

  • "docker push wget", you'll see that authentication required and what this did here is that it

  • was trying to say that you're going to push to "library", this is for the official packages,

  • and then it's saying that you're not allowed to do that.

  • So for me, my username on Docker hub is "keiththomps" so we're actually going to tag "wget" as "keiththomps/wget".

  • Now if we look at "docker images" again you'll see that I have "wget" and that I have "keiththomps/wget"

  • and they're the exact same thing, they point to the exact same SHA, they're just two names

  • for the same thing.

  • So from here we'll try to push this.

  • Ahh "Authentication required" again, so this is because you need to be authenticated with

  • Docker in order to push to Docker hub, but not to pull from Docker hub.

  • So to do this you use "docker login", my username's "keiththomps", and I'm going to paste in my

  • password.

  • Alright, it logged in successfully, so if we go back and we try to push this again we'll

  • see what happens.

  • So right now it's going to go off and push each layer, and each layer has a little bit

  • of weight to it.

  • I'm going to chop out the bit while it's uploading and then we can continue after it's done.

  • Now that it's finished, we can go back to Docker hub and see if it uploaded properly.

  • Docker hub isn't the fastest website on the planet, so you have to bear with it sometimes

  • when it takes awhile.

  • Alright, there it is.

  • So we've successfully gone from having Docker not installed on our machine, to installing

  • Docker through Docker for Mac (although there are other ways to install it), to downloading

  • our first image and building our first container, to creating our first image and building a

  • container with that image, and then uploading that image so that other people can share.

  • I hope you enjoyed this, and if you did I would appreciate any feedback you've got and

  • if you want to subscribe or like the video then that would be great too.

Today we're going to talk about Docker.

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A2 初級

Dockerの基本を学ぶ (Learn the Basics of Docker)

  • 56 9
    MingEn Wu に公開 2021 年 01 月 14 日
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