1 00:00:02,080 --> 00:00:04,220 To build this custom image, 2 00:00:04,220 --> 00:00:07,280 we need to go to the folder that contains our code. 3 00:00:07,280 --> 00:00:10,350 And in there we need to create a new file. 4 00:00:10,350 --> 00:00:12,480 A file named Dockerfile. 5 00:00:13,710 --> 00:00:17,910 This is a special name which will be identified by Docker. 6 00:00:17,910 --> 00:00:20,320 Now to get the best possible support 7 00:00:20,320 --> 00:00:22,570 for writing such Docker files, 8 00:00:22,570 --> 00:00:25,670 I recommend that in Visual Studio Code, 9 00:00:25,670 --> 00:00:28,840 you go to the extensions area, 10 00:00:28,840 --> 00:00:31,230 and there you search for Docker 11 00:00:31,230 --> 00:00:34,410 and you install this Docker extension 12 00:00:34,410 --> 00:00:36,200 which I already have here. 13 00:00:36,200 --> 00:00:39,180 Make sure you install this Docker extension 14 00:00:39,180 --> 00:00:41,870 because this will help you with writing Docker 15 00:00:41,870 --> 00:00:43,950 called Docker instructions. 16 00:00:43,950 --> 00:00:47,390 It's not a must have but it will make your life easier. 17 00:00:47,390 --> 00:00:50,750 And thereafter you can go back to the explorer view. 18 00:00:50,750 --> 00:00:52,200 So now we got this Dockerfile 19 00:00:53,300 --> 00:00:56,350 and what do we put into this file now? 20 00:00:56,350 --> 00:01:00,750 This file will contain the instructions for Docker 21 00:01:00,750 --> 00:01:05,069 that we wanna execute when we build our own image. 22 00:01:05,069 --> 00:01:09,170 So it contains the setup instructions for our own image. 23 00:01:09,170 --> 00:01:13,890 And typically here you start with the FROM instruction. 24 00:01:13,890 --> 00:01:16,530 All caps FROM. 25 00:01:16,530 --> 00:01:19,980 This allows you to build your image 26 00:01:19,980 --> 00:01:22,377 up on another base image. 27 00:01:22,377 --> 00:01:24,590 And this is what you typically do. 28 00:01:24,590 --> 00:01:25,980 Theoretically of course 29 00:01:25,980 --> 00:01:29,010 you could build a Docker image from scratch, 30 00:01:29,010 --> 00:01:31,070 but you always want some kind 31 00:01:31,070 --> 00:01:33,610 of operating system layer in there, 32 00:01:33,610 --> 00:01:37,920 one some kind of other tool, which your code needs. 33 00:01:37,920 --> 00:01:41,430 So therefore here I wanna build up on the node image. 34 00:01:41,430 --> 00:01:44,263 And I can do this with, from node, 35 00:01:45,140 --> 00:01:47,800 just entering the image name of an image 36 00:01:47,800 --> 00:01:50,420 which either exists on your system, 37 00:01:50,420 --> 00:01:54,370 or under that name on Docker hub. 38 00:01:54,370 --> 00:01:57,150 And this image now exists on Docker hub. 39 00:01:57,150 --> 00:02:00,430 And actually since we already executed a container based 40 00:02:00,430 --> 00:02:03,280 on this image at the moment it also exists 41 00:02:03,280 --> 00:02:06,460 on our local machine because when we ran a container 42 00:02:06,460 --> 00:02:09,539 based on this Docker hub image for the first time, 43 00:02:09,539 --> 00:02:13,120 this image was downloaded and cached locally. 44 00:02:13,120 --> 00:02:15,680 So now this is basically both a local 45 00:02:15,680 --> 00:02:17,590 and a Docker hub image. 46 00:02:17,590 --> 00:02:19,660 The most important thing is though 47 00:02:19,660 --> 00:02:21,270 that it will be recognized. 48 00:02:21,270 --> 00:02:25,470 That node is a name Docker will be able to find 49 00:02:25,470 --> 00:02:28,123 that there will be an image named node. 50 00:02:29,470 --> 00:02:33,460 So now we're telling Docker, hey, in my own image, 51 00:02:33,460 --> 00:02:37,560 I wanna start by pulling in that node image, 52 00:02:37,560 --> 00:02:38,963 and then I wanna continue. 53 00:02:39,870 --> 00:02:43,450 So that's not the first step, as a next step, 54 00:02:43,450 --> 00:02:45,380 we wanna tell Docker 55 00:02:45,380 --> 00:02:49,710 which files that live here on our local machine 56 00:02:49,710 --> 00:02:51,820 should go into the image. 57 00:02:51,820 --> 00:02:55,080 And for Docker get to copy command. 58 00:02:55,080 --> 00:02:58,710 And here a very simple instruction we could execute, 59 00:02:58,710 --> 00:03:01,530 is copy.dot. 60 00:03:01,530 --> 00:03:03,210 Now what does this mean? 61 00:03:03,210 --> 00:03:06,750 You basically specify two paths here. 62 00:03:06,750 --> 00:03:10,620 The first path is to path outside of the container, 63 00:03:10,620 --> 00:03:13,920 outside of the image where the files leave 64 00:03:13,920 --> 00:03:16,003 that should be copied into the image. 65 00:03:16,860 --> 00:03:19,300 And if you just specify a dot here 66 00:03:19,300 --> 00:03:22,800 that basically tells Docker that it's the same folder 67 00:03:22,800 --> 00:03:25,180 that contains the Dockerfile. 68 00:03:25,180 --> 00:03:27,090 Excluding the Dockerfile though. 69 00:03:27,090 --> 00:03:29,630 So in this case dot would tell Docker 70 00:03:29,630 --> 00:03:32,270 this first dot would tell Docker 71 00:03:32,270 --> 00:03:35,340 that all the folders, sub folders 72 00:03:35,340 --> 00:03:39,323 and files here in this project should be copied into DMH. 73 00:03:40,241 --> 00:03:44,690 And now the second dot is the path inside of the image 74 00:03:44,690 --> 00:03:46,833 where those files should be stored. 75 00:03:48,030 --> 00:03:50,810 Every image and for also every container 76 00:03:50,810 --> 00:03:52,730 created based on an image, 77 00:03:52,730 --> 00:03:55,920 has its own internal file system 78 00:03:55,920 --> 00:03:57,500 which is totally detached 79 00:03:57,500 --> 00:04:00,520 from your file system on your machine. 80 00:04:00,520 --> 00:04:04,530 It's hidden away inside of the Docker container. 81 00:04:04,530 --> 00:04:07,280 And actually here it is a good idea to not use 82 00:04:07,280 --> 00:04:12,280 the root folder, the root entry in your Docker container 83 00:04:12,350 --> 00:04:15,480 but some sub folder which is totally up to you. 84 00:04:15,480 --> 00:04:17,149 You can name it however you want. 85 00:04:17,149 --> 00:04:20,700 And here I will name this slash app. 86 00:04:20,700 --> 00:04:25,700 Now all the files here in the same folder as the Dockerfile 87 00:04:25,860 --> 00:04:28,410 and all the sub folders there as well, 88 00:04:28,410 --> 00:04:33,170 will be copied into an app folder inside of the container. 89 00:04:33,170 --> 00:04:35,830 And this folder will simply be created 90 00:04:35,830 --> 00:04:39,043 in the image and container if it doesn't exist yet. 91 00:04:40,050 --> 00:04:41,773 So that's one key step. 92 00:04:43,020 --> 00:04:47,920 Now, as a next step, we need to run NPM install, right? 93 00:04:47,920 --> 00:04:49,660 Because that is what we had to do 94 00:04:49,660 --> 00:04:51,560 outside of the container as well. 95 00:04:51,560 --> 00:04:56,020 For node applications, we had to run NPM install 96 00:04:56,020 --> 00:04:59,080 in order to install all the dependencies 97 00:04:59,080 --> 00:05:00,803 of our node application. 98 00:05:01,930 --> 00:05:04,060 And you also have an instruction for that, 99 00:05:04,060 --> 00:05:05,610 which you can give to Docker. 100 00:05:05,610 --> 00:05:09,520 You can tell it to after copying all the local files 101 00:05:09,520 --> 00:05:14,520 into the image, you want to run a command in the image. 102 00:05:14,670 --> 00:05:17,063 In this case, NPM install. 103 00:05:18,040 --> 00:05:20,330 However, there is a gotcha here. 104 00:05:20,330 --> 00:05:23,260 By default, all those commands 105 00:05:23,260 --> 00:05:26,880 will be executed in the working directory 106 00:05:26,880 --> 00:05:29,540 off your Docker container and image. 107 00:05:29,540 --> 00:05:34,060 And by default, that working directory is the root folder 108 00:05:34,060 --> 00:05:36,750 in that container file system. 109 00:05:36,750 --> 00:05:40,400 Since I'm copying my code into the app folder here 110 00:05:40,400 --> 00:05:42,770 I actually want to run NPM install 111 00:05:42,770 --> 00:05:45,700 inside of the app folder as well. 112 00:05:45,700 --> 00:05:47,550 And a convenient way of telling Docker 113 00:05:47,550 --> 00:05:51,290 that all commands should be executed in that folder, 114 00:05:51,290 --> 00:05:55,270 is that you set another instruction here 115 00:05:55,270 --> 00:05:57,210 before you copy everything. 116 00:05:57,210 --> 00:06:00,210 And that's the workdir instruction 117 00:06:00,210 --> 00:06:03,820 for a setting the working directory of the Docker container 118 00:06:03,820 --> 00:06:06,400 and setting this to slash app. 119 00:06:06,400 --> 00:06:09,760 And this tells Docker that all the subsequent commands 120 00:06:09,760 --> 00:06:13,920 will be executed from inside that folder. 121 00:06:13,920 --> 00:06:16,130 Which makes sense because that is 122 00:06:16,130 --> 00:06:18,170 where we will have our code later. 123 00:06:18,170 --> 00:06:23,170 And now as a side node, given the fact that we now did set 124 00:06:23,400 --> 00:06:26,170 the working directory to slash app, 125 00:06:26,170 --> 00:06:29,810 we could also change copy to copy 126 00:06:29,810 --> 00:06:33,410 everything from the path to Docker file is in, 127 00:06:33,410 --> 00:06:37,670 to just dot or dot slash which basically means 128 00:06:37,670 --> 00:06:40,680 due to current working directory 129 00:06:40,680 --> 00:06:43,320 inside of our Docker container. 130 00:06:43,320 --> 00:06:47,310 Since we changed that working directory to slash app 131 00:06:47,310 --> 00:06:52,310 not just to run, but also copy will execute relative 132 00:06:52,480 --> 00:06:54,280 to this working directory. 133 00:06:54,280 --> 00:06:58,810 So now inside of the container internal file system 134 00:06:58,810 --> 00:07:03,810 this relative path now points at slash app. 135 00:07:03,860 --> 00:07:05,720 But we can also be more explicit here 136 00:07:05,720 --> 00:07:10,510 and set this to the absolute slash app path like this. 137 00:07:10,510 --> 00:07:14,240 And I'm a fan of doing that since this makes it very clear 138 00:07:14,240 --> 00:07:16,740 where we're going to copy our files, 139 00:07:16,740 --> 00:07:20,350 and we don't have to guess or look into that file 140 00:07:20,350 --> 00:07:24,020 to see what the current working directory is. 141 00:07:24,020 --> 00:07:26,060 Of course that is a simple file. 142 00:07:26,060 --> 00:07:28,500 It's easy to see what the workdir is, 143 00:07:28,500 --> 00:07:30,560 but if this would be a more complex file, 144 00:07:30,560 --> 00:07:31,990 it could be harder. 145 00:07:31,990 --> 00:07:34,160 And therefore I personally prefer 146 00:07:34,160 --> 00:07:37,260 setting this to slash app here as well. 147 00:07:37,260 --> 00:07:38,260 Now with that, 148 00:07:38,260 --> 00:07:41,120 we have a lot of important setup instructions. 149 00:07:41,120 --> 00:07:45,130 The last instruction is that when all of that is done, 150 00:07:45,130 --> 00:07:48,360 we want to start our server. 151 00:07:48,360 --> 00:07:51,290 For that we could add run node server 152 00:07:51,290 --> 00:07:55,130 but this would actually be incorrect node server.js. 153 00:07:55,130 --> 00:07:58,210 This would be incorrect because this would be executed 154 00:07:58,210 --> 00:08:01,610 whenever this image is being built. 155 00:08:01,610 --> 00:08:05,270 All these here are instructions to Docker 156 00:08:05,270 --> 00:08:07,480 for setting up the image. 157 00:08:07,480 --> 00:08:11,100 Now keep in mind the image should be the template 158 00:08:11,100 --> 00:08:12,270 for the container. 159 00:08:12,270 --> 00:08:14,960 The image is not what you run in the end, 160 00:08:14,960 --> 00:08:18,790 you run a container based on an image. 161 00:08:18,790 --> 00:08:21,310 And therefore with this command, 162 00:08:21,310 --> 00:08:24,760 we would try to start the server in the image, 163 00:08:24,760 --> 00:08:27,950 so in the template, but that's not what we want. 164 00:08:27,950 --> 00:08:31,200 We want to install all the dependencies there, yes, 165 00:08:31,200 --> 00:08:33,960 we want to have all the code in there, yes, 166 00:08:33,960 --> 00:08:36,580 but we only wanna start a server 167 00:08:36,580 --> 00:08:40,260 if we start a container based on an image. 168 00:08:40,260 --> 00:08:44,020 Also so that if we start multiple containers 169 00:08:44,020 --> 00:08:46,260 on one and the same image, 170 00:08:46,260 --> 00:08:49,410 we also start multiple node servers. 171 00:08:49,410 --> 00:08:51,870 So therefore here we have another instruction 172 00:08:51,870 --> 00:08:55,443 and that's the CMD instruction, which stands for a command. 173 00:08:56,310 --> 00:09:00,550 The difference to run is that this will now not be executed 174 00:09:00,550 --> 00:09:02,540 when the image is created, 175 00:09:02,540 --> 00:09:06,563 but when a container is started based on the image. 176 00:09:07,450 --> 00:09:08,560 And that's what we want. 177 00:09:08,560 --> 00:09:11,483 Then we want to run our node server. 178 00:09:12,830 --> 00:09:16,550 However, for CMD, the syntax is a bit differently. 179 00:09:16,550 --> 00:09:20,170 Here we wanna pass an array you could say, 180 00:09:20,170 --> 00:09:22,500 and then we have two strings in there 181 00:09:22,500 --> 00:09:24,943 where we split our command like this. 182 00:09:25,940 --> 00:09:28,510 So that's how we now tell Docker 183 00:09:28,510 --> 00:09:30,490 that whenever a container is created 184 00:09:30,490 --> 00:09:33,840 based on that image, we use the node command, 185 00:09:33,840 --> 00:09:37,040 which exists inside of that container 186 00:09:37,040 --> 00:09:39,043 to run the server js file. 187 00:09:39,910 --> 00:09:42,290 Now if we want to try to run it like this, 188 00:09:42,290 --> 00:09:45,650 we would not be able to see our application though 189 00:09:45,650 --> 00:09:47,980 for one key reason. 190 00:09:47,980 --> 00:09:52,980 This node web server listens on port 80. 191 00:09:53,060 --> 00:09:57,160 And I mentioned and emphasized multiple times already 192 00:09:57,160 --> 00:09:59,780 that a Docker container is isolated. 193 00:09:59,780 --> 00:10:03,460 It's isolated from our local environment. 194 00:10:03,460 --> 00:10:08,250 And as a result, it also has its own internal network. 195 00:10:08,250 --> 00:10:10,890 And when we listen to port 80 196 00:10:10,890 --> 00:10:14,290 in the node application inside of our container, 197 00:10:14,290 --> 00:10:17,650 the container does not expose that port 198 00:10:17,650 --> 00:10:19,760 to our local machine. 199 00:10:19,760 --> 00:10:22,410 So we won't be able to listen on the port 200 00:10:22,410 --> 00:10:27,140 just because something's listening inside of a container. 201 00:10:27,140 --> 00:10:30,980 Therefore in the Docker file after setting everything up, 202 00:10:30,980 --> 00:10:33,280 before specifying the command, 203 00:10:33,280 --> 00:10:36,110 which should always be the last instruction 204 00:10:36,110 --> 00:10:37,990 in your Dockerfile, 205 00:10:37,990 --> 00:10:42,140 we can add to the expose instruction to let Docker know 206 00:10:42,140 --> 00:10:44,750 that when this container is started, 207 00:10:44,750 --> 00:10:49,750 we wanna expose a certain port to our local system. 208 00:10:50,360 --> 00:10:53,670 So to our machine here which will run this container. 209 00:10:53,670 --> 00:10:55,530 And then we'll be able to run 210 00:10:55,530 --> 00:10:58,133 the container (indistinct) we listen on this port. 211 00:10:59,620 --> 00:11:02,520 Now with that, we finished our Dockerfile 212 00:11:02,520 --> 00:11:06,350 with all the setup instructions for a Docker image. 213 00:11:06,350 --> 00:11:10,130 Now let's see how we can utilize this custom image. 214 00:11:10,130 --> 00:11:12,123 build it and how we can run it.