1 00:00:02,200 --> 00:00:07,140 I mentioned that containers are based on images. 2 00:00:07,140 --> 00:00:09,630 And actually, there will be two ways 3 00:00:09,630 --> 00:00:12,100 of creating or getting an image 4 00:00:12,100 --> 00:00:14,220 so that we then can run a container. 5 00:00:14,220 --> 00:00:18,810 The first way is that we use an already existing image. 6 00:00:18,810 --> 00:00:22,210 For example, because a colleague of ours already built it, 7 00:00:22,210 --> 00:00:25,030 or also very common, because we use 8 00:00:25,030 --> 00:00:28,310 one of the official pre-built images 9 00:00:28,310 --> 00:00:31,680 or one of the images shared by the community. 10 00:00:31,680 --> 00:00:34,950 And a great source for that would be Docker Hub, 11 00:00:34,950 --> 00:00:39,330 which you can simply Google to find hub.docker.com. 12 00:00:39,330 --> 00:00:41,540 And there you can log in 13 00:00:41,540 --> 00:00:44,010 but you don't need to do this right now. 14 00:00:44,010 --> 00:00:45,870 Instead, here in the search bar, 15 00:00:45,870 --> 00:00:48,910 we can, for example, search for node. 16 00:00:48,910 --> 00:00:53,400 And what we'll find is the official node Docker image, 17 00:00:53,400 --> 00:00:57,880 which we could use to build a node application container, 18 00:00:57,880 --> 00:01:01,723 a container which will later run a node application. 19 00:01:02,790 --> 00:01:07,540 Now this node image which you find on Docker Hub, 20 00:01:07,540 --> 00:01:12,510 can be used by anyone and it is distributed and created 21 00:01:12,510 --> 00:01:16,570 and maintained by the official node team. 22 00:01:16,570 --> 00:01:20,790 Now we will use such official images a lot throughout 23 00:01:20,790 --> 00:01:24,900 this course and in general when working with Docker, 24 00:01:24,900 --> 00:01:28,270 but we can especially use it right away to get started 25 00:01:28,270 --> 00:01:30,680 with images and containers here. 26 00:01:30,680 --> 00:01:33,950 And all we need to do for that is open up 27 00:01:33,950 --> 00:01:38,950 the command prompt or terminal on your system 28 00:01:39,040 --> 00:01:43,490 and then navigate in any folder of your choice 29 00:01:43,490 --> 00:01:48,053 and run docker run node. 30 00:01:49,680 --> 00:01:54,050 This command here will use this node image 31 00:01:54,050 --> 00:01:59,050 which we find on Docker Hub and it will utilize it 32 00:01:59,460 --> 00:02:04,060 to create a so called container based on this image, 33 00:02:04,060 --> 00:02:07,320 because as I mentioned, containers are really just 34 00:02:07,320 --> 00:02:10,550 the running instances of images. 35 00:02:10,550 --> 00:02:14,550 Images contain the setup code the environment, 36 00:02:14,550 --> 00:02:18,490 in this case, the node image contains the node installation. 37 00:02:18,490 --> 00:02:22,890 And then we can run the image to run the application 38 00:02:22,890 --> 00:02:27,890 or in this case, to simply run the node interactive shell. 39 00:02:29,990 --> 00:02:33,020 Now if you hit Enter, this will give you an error 40 00:02:33,020 --> 00:02:35,680 that it doesn't find this image locally, 41 00:02:35,680 --> 00:02:38,110 which makes sense because it's on Docker Hub, 42 00:02:38,110 --> 00:02:42,520 and then it'll automatically pull it from Docker Hub. 43 00:02:42,520 --> 00:02:47,520 So now this downloads the latest node image from Docker Hub 44 00:02:48,100 --> 00:02:52,430 and once it downloaded it locally onto our machine, 45 00:02:52,430 --> 00:02:55,820 it will run this image as a container. 46 00:02:55,820 --> 00:02:58,200 So let's wait for this download to finish here 47 00:03:00,200 --> 00:03:03,930 and thereafter, you will see nothing special here. 48 00:03:03,930 --> 00:03:07,070 It's done and we can enter more commands. 49 00:03:07,070 --> 00:03:10,390 So did we now run the container? 50 00:03:10,390 --> 00:03:13,173 Did we now create a container based on an image? 51 00:03:14,040 --> 00:03:15,500 Well, yes, we did. 52 00:03:15,500 --> 00:03:18,270 But this container isn't really doing much. 53 00:03:18,270 --> 00:03:22,740 Node is of course just a software you could say 54 00:03:22,740 --> 00:03:27,740 and indeed we can execute node to get an interactive shell 55 00:03:28,040 --> 00:03:30,160 where we can insert command. 56 00:03:30,160 --> 00:03:33,380 But by default, and that's important, 57 00:03:33,380 --> 00:03:37,630 a container is isolated from the surrounding environment 58 00:03:37,630 --> 00:03:40,970 and just because there might be some interactive shell 59 00:03:40,970 --> 00:03:43,160 running inside of a container 60 00:03:43,160 --> 00:03:48,160 does not mean that this shell is exposed to us as a user. 61 00:03:49,730 --> 00:03:53,060 Nonetheless, this container was created. 62 00:03:53,060 --> 00:03:57,630 And you can tell by running Docker PS dash A. 63 00:03:57,630 --> 00:04:02,140 PS stands for processes and with the dash A flag, 64 00:04:02,140 --> 00:04:06,290 this will show you all the processes all the containers 65 00:04:06,290 --> 00:04:08,450 Docker created for us. 66 00:04:08,450 --> 00:04:12,045 And if you hit enter, you will see that a minute ago 67 00:04:12,045 --> 00:04:15,760 I actually created a container. 68 00:04:15,760 --> 00:04:17,120 And to make this a bit easier to read 69 00:04:17,120 --> 00:04:19,403 I'll zoom out a bit and rerun this. 70 00:04:20,440 --> 00:04:24,280 And you'll see we created a container with this ID. 71 00:04:24,280 --> 00:04:27,150 The image was the node image. 72 00:04:27,150 --> 00:04:29,570 It was created two minutes ago, 73 00:04:29,570 --> 00:04:32,550 it exited so it's not running anymore 74 00:04:32,550 --> 00:04:36,070 and it also received a automatically generated name. 75 00:04:36,070 --> 00:04:39,260 We'll dive into names and into configuring containers 76 00:04:39,260 --> 00:04:42,410 in general in greater detail later. 77 00:04:42,410 --> 00:04:44,690 But what we see is that something happened 78 00:04:44,690 --> 00:04:46,700 but that it's not running anymore 79 00:04:46,700 --> 00:04:50,350 because as I said a container runs in isolation. 80 00:04:50,350 --> 00:04:55,350 And even though we executed node as a image 81 00:04:55,800 --> 00:04:58,630 or as a container based on the node image, 82 00:04:58,630 --> 00:05:00,510 this alone doesn't do much. 83 00:05:00,510 --> 00:05:04,360 Because the interactive shell exposed by node 84 00:05:04,360 --> 00:05:08,960 is not automatically exposed by the container to us. 85 00:05:08,960 --> 00:05:12,140 That is something we can change though. 86 00:05:12,140 --> 00:05:16,630 If we repeat the command from before, docker run node, 87 00:05:16,630 --> 00:05:19,800 and we now add an extra flag in front of node, 88 00:05:19,800 --> 00:05:24,040 the dash IT flag, then we will actually tell Docker 89 00:05:24,040 --> 00:05:28,090 that we wanna expose an interactive session 90 00:05:28,090 --> 00:05:31,710 from inside the container to our hosting machine. 91 00:05:31,710 --> 00:05:33,980 And hence if we now hit enter, 92 00:05:33,980 --> 00:05:38,450 we actually are in that interactive node terminal 93 00:05:38,450 --> 00:05:41,520 where we can run basic node commands. 94 00:05:41,520 --> 00:05:43,290 For example, one plus one, 95 00:05:43,290 --> 00:05:45,980 but we could also use node API's in here. 96 00:05:45,980 --> 00:05:50,610 But that's of course not the focus of this session. 97 00:05:50,610 --> 00:05:53,740 Now the important thing about this here is that 98 00:05:53,740 --> 00:05:58,450 node here is now running inside of that created container 99 00:05:58,450 --> 00:06:02,730 and it's just exposed to us by adding this extra flag 100 00:06:02,730 --> 00:06:05,150 so we can interact with that container 101 00:06:05,150 --> 00:06:08,480 and with node running in the container. 102 00:06:08,480 --> 00:06:12,560 Node is not running on our machine here 103 00:06:12,560 --> 00:06:14,120 and I can prove this. 104 00:06:14,120 --> 00:06:18,490 Please note that here we're interacting with node 14.9, 105 00:06:18,490 --> 00:06:22,130 which is the version that at the moment I was recording this 106 00:06:22,130 --> 00:06:24,400 was pulled into this image, 107 00:06:24,400 --> 00:06:27,620 and therefore is being used in this container. 108 00:06:27,620 --> 00:06:32,320 Now if I quit this process with Control + C pressed twice 109 00:06:32,320 --> 00:06:34,620 now the container will shut down, 110 00:06:34,620 --> 00:06:38,440 when I quit this and I run node dash V here 111 00:06:38,440 --> 00:06:42,650 like this on my system so not inside of the container, 112 00:06:42,650 --> 00:06:45,170 I see 14.7 as a version. 113 00:06:45,170 --> 00:06:49,250 So locally on my system I got a different version installed, 114 00:06:49,250 --> 00:06:51,690 then the version we interacted with here, 115 00:06:51,690 --> 00:06:55,200 which proves that the version we did interact with 116 00:06:55,200 --> 00:06:58,190 must be the version from inside the container. 117 00:06:58,190 --> 00:07:02,650 And we don't need node to be installed on our system at all 118 00:07:02,650 --> 00:07:05,480 in order to be able to run this node container 119 00:07:05,480 --> 00:07:06,803 and interact with it. 120 00:07:07,740 --> 00:07:11,310 And that is really how you work with containers. 121 00:07:11,310 --> 00:07:13,760 At least these are some first steps 122 00:07:13,760 --> 00:07:15,710 of working with containers, 123 00:07:15,710 --> 00:07:19,590 and this also shows us what images and containers are. 124 00:07:19,590 --> 00:07:22,920 Images are used behind the scenes 125 00:07:22,920 --> 00:07:26,770 to hold all the logic and all the code a container needs, 126 00:07:26,770 --> 00:07:30,600 and then we create instances of an image 127 00:07:30,600 --> 00:07:32,420 with the Run command. 128 00:07:32,420 --> 00:07:35,070 This creates then the concrete containers 129 00:07:35,070 --> 00:07:37,400 which are based on an image. 130 00:07:37,400 --> 00:07:42,350 And if we now run Docker PS dash A again, 131 00:07:42,350 --> 00:07:45,370 we see that we get two containers now. 132 00:07:45,370 --> 00:07:49,330 Both are not running anymore, they have been exited. 133 00:07:49,330 --> 00:07:53,990 But we have more than one container based on the same image. 134 00:07:53,990 --> 00:07:57,090 Both containers are based on the same image. 135 00:07:57,090 --> 00:07:59,520 And yes, they are not running anymore 136 00:07:59,520 --> 00:08:03,100 but we could absolutely have two containers which are based 137 00:08:03,100 --> 00:08:06,360 on the same image up and running at the same point of time, 138 00:08:06,360 --> 00:08:09,220 simply by opening up multiple terminals 139 00:08:09,220 --> 00:08:12,660 and then while repeating this docker run command. 140 00:08:12,660 --> 00:08:14,940 This would absolutely be possible. 141 00:08:14,940 --> 00:08:17,780 And that's the idea behind images and containers. 142 00:08:17,780 --> 00:08:21,860 Images contain the code, the setup, the meet, you could say 143 00:08:21,860 --> 00:08:25,027 and containers are then the running instances 144 00:08:25,027 --> 00:08:26,503 of those images.