WEBVTT 00:01.050 --> 00:01.883 -: In the last section, 00:01.883 --> 00:04.290 we broke down the contents of our Docker file 00:04.290 --> 00:06.840 and got an understanding of the overall contents 00:06.840 --> 00:08.250 or structure of it. 00:08.250 --> 00:10.260 We now know that there's a handful of instructions 00:10.260 --> 00:13.260 that we can use to customize how our image is built. 00:13.260 --> 00:15.480 These are three of the most important instructions to know 00:15.480 --> 00:18.630 and we'll introduce a handful of other ones over time. 00:18.630 --> 00:19.463 In this section, 00:19.463 --> 00:22.020 I now want to kind of break down what was really occurring 00:22.020 --> 00:24.660 behind the scenes with each of these instructions. 00:24.660 --> 00:25.650 We're gonna first begin 00:25.650 --> 00:28.020 by taking a look at a little analogy. 00:28.020 --> 00:29.670 So, this is going to be an analogy 00:29.670 --> 00:32.490 to help you understand the structure or purpose 00:32.490 --> 00:36.030 of those lines of configuration inside that Docker file. 00:36.030 --> 00:37.650 So, quick analogy, 00:37.650 --> 00:39.689 I'm gonna tell you writing a Docker file 00:39.689 --> 00:43.890 is a little bit just like being given a computer. 00:43.890 --> 00:47.670 So, a brand new computer with no operating system on it 00:47.670 --> 00:50.790 and being told to install Google Chrome on there. 00:50.790 --> 00:53.040 So, I want you to imagine what you would do 00:53.040 --> 00:54.960 if I handed you a computer 00:54.960 --> 00:56.820 that has no operating system on it, 00:56.820 --> 01:00.600 and I told you, you have to install Google Chrome on here. 01:00.600 --> 01:03.600 Well, here is probably what you would end up doing. 01:03.600 --> 01:04.860 The first thing you might do 01:04.860 --> 01:07.980 is try turning on that laptop or turning on that desktop. 01:07.980 --> 01:09.150 And when you turned it on, 01:09.150 --> 01:11.580 you would probably maybe see some boot-up process 01:11.580 --> 01:13.680 but then you would eventually be given a message 01:13.680 --> 01:14.767 that says something like, 01:14.767 --> 01:18.720 "Hey, sorry, no bootable drive or no operating system. 01:18.720 --> 01:20.160 I'm just an empty computer. 01:20.160 --> 01:21.600 I don't know what to do." 01:21.600 --> 01:23.310 So, the first thing you would probably do 01:23.310 --> 01:25.440 is install an operating system. 01:25.440 --> 01:27.990 You need an operating system on that computer 01:27.990 --> 01:31.470 in order to go through all these sequential steps on here. 01:31.470 --> 01:33.060 If you wanna download Google Chrome, 01:33.060 --> 01:34.950 you have to go and download it from somewhere 01:34.950 --> 01:36.720 by opening up your web browser, 01:36.720 --> 01:39.600 and you have to navigate to chrome.google.com. 01:39.600 --> 01:42.990 You have to download the installer and open a file explorer, 01:42.990 --> 01:45.180 and then execute that installer. 01:45.180 --> 01:47.520 So, those series of steps right there, 01:47.520 --> 01:51.150 those are all steps that are facilitated by the installation 01:51.150 --> 01:53.160 of that initial operating system. 01:53.160 --> 01:54.870 If you didn't have an operating system, 01:54.870 --> 01:58.020 there would be no default browser to start up. 01:58.020 --> 02:01.710 You would not have a file or folder explorer to start up 02:01.710 --> 02:03.630 and you probably would not have any way 02:03.630 --> 02:05.820 to run an executable file. 02:05.820 --> 02:07.680 All of these steps are kind of proceeded 02:07.680 --> 02:11.673 or dependent upon having an initial operating system. 02:12.990 --> 02:14.790 So, then going through all those initial steps, 02:14.790 --> 02:15.623 eventually, 02:15.623 --> 02:18.060 you would be able to execute the Chrome executable 02:18.060 --> 02:20.040 and start up that browser. 02:20.040 --> 02:22.290 So, these steps right here, 02:22.290 --> 02:26.100 very similar to what we just did inside that Docker file. 02:26.100 --> 02:29.100 When we specify that base image of Alpine, 02:29.100 --> 02:32.940 that was a lot like installing an initial operating system. 02:32.940 --> 02:34.950 By default, when we create a container, 02:34.950 --> 02:35.783 or excuse me, 02:35.783 --> 02:38.370 when we create an image, we have an empty image. 02:38.370 --> 02:39.900 There's really nothing inside. 02:39.900 --> 02:41.340 There are no infrastructure, 02:41.340 --> 02:44.760 no programs that we can use to navigate around a file 02:44.760 --> 02:45.870 or folder system. 02:45.870 --> 02:48.330 There's nothing we can use to download or install, 02:48.330 --> 02:49.800 or configure dependencies. 02:49.800 --> 02:51.360 There's nothing in there. 02:51.360 --> 02:54.240 So, the purpose of a specifying a base image 02:54.240 --> 02:56.640 is to kind of give us an initial starting point, 02:56.640 --> 02:59.280 or an initial set of programs that we can use 02:59.280 --> 03:01.770 to further customize our image. 03:01.770 --> 03:04.920 So, that is the purpose of that first line, 03:04.920 --> 03:06.510 d from Alpine. 03:06.510 --> 03:10.050 We said that we wanted to use the Alpine Docker image 03:10.050 --> 03:12.150 as kind of an initial operating system 03:12.150 --> 03:15.810 or a starting point for the image that we are creating. 03:15.810 --> 03:18.397 Now, your very initial follow up question might be, 03:18.397 --> 03:20.130 "Well, why did we use Alpine? 03:20.130 --> 03:21.360 What is Alpine?" 03:21.360 --> 03:22.890 So, that's a good question. 03:22.890 --> 03:24.517 Another brief aside, 03:24.517 --> 03:27.330 "Why did we use Alpine as a base image?" 03:27.330 --> 03:28.260 Well, back to you. 03:28.260 --> 03:29.850 I'm gonna kind of post a question. 03:29.850 --> 03:30.937 I'm gonna say to you, 03:30.937 --> 03:34.830 "Why do you use Windows, or Mac OS, or Ubuntu, 03:34.830 --> 03:38.040 or some other Linux distribution on your personal computer?" 03:38.040 --> 03:42.210 The answer is that you use any particular operating system 03:42.210 --> 03:44.580 because it kinda suits your needs. 03:44.580 --> 03:46.890 Windows might have a program that you need 03:46.890 --> 03:49.080 to use your computer effectively. 03:49.080 --> 03:51.840 You might use Mac OS because it has a built in Terminal 03:51.840 --> 03:53.700 and that's really nice for you. 03:53.700 --> 03:54.533 In other words, 03:54.533 --> 03:57.180 you use one of these default operating systems 03:57.180 --> 03:59.460 because it has a set of pre-installed programs 03:59.460 --> 04:03.600 that is useful to you and what you are trying to accomplish. 04:03.600 --> 04:05.610 So, we just made use of Alpine 04:05.610 --> 04:09.300 as a base image as kind of like an operating system of sorts 04:09.300 --> 04:12.510 because it includes a default set of programs 04:12.510 --> 04:13.620 that are very useful 04:13.620 --> 04:16.050 for what you and I are trying to accomplish. 04:16.050 --> 04:18.720 We are trying to install and run Redis, 04:18.720 --> 04:20.070 and the Alpine base image 04:20.070 --> 04:21.930 has a set of programs inside of it 04:21.930 --> 04:26.370 that are very useful for installing and running Redis. 04:26.370 --> 04:28.230 The command or the program 04:28.230 --> 04:29.760 that was most useful for you and I 04:29.760 --> 04:31.256 for installing and running Redis 04:31.256 --> 04:34.740 was found on the second line of the Docker file. 04:34.740 --> 04:38.340 We had said, "RUN apk, add update redis." 04:38.340 --> 04:40.500 This is not a Docker command right here. 04:40.500 --> 04:44.490 This line has nothing to do with Docker, whatsoever. 04:44.490 --> 04:49.490 APK is a program called Apache Package something, I think? 04:50.070 --> 04:52.920 It is a package manager that comes pre-installed 04:52.920 --> 04:54.540 on the Alpine image, 04:54.540 --> 04:56.520 and we can use that package manager 04:56.520 --> 04:59.700 that is built into Alpine to automatically download 04:59.700 --> 05:01.530 and install Redis for us. 05:01.530 --> 05:03.150 So, we made use of Alpine 05:03.150 --> 05:05.940 because it had this package manager program 05:05.940 --> 05:07.860 automatically included inside of it. 05:07.860 --> 05:09.990 And so, it made it a very convenient thing 05:09.990 --> 05:12.990 to start with inside of our Docker file. 05:12.990 --> 05:15.300 All right, so I think we've got a better idea 05:15.300 --> 05:17.160 of what's going on with this front line, 05:17.160 --> 05:19.320 and I think we've got kind of a reasonable idea 05:19.320 --> 05:21.780 of at least the right hand side of this one. 05:21.780 --> 05:24.390 You know, the actual like command or line of code 05:24.390 --> 05:25.380 that was executed. 05:25.380 --> 05:27.390 But we still need to have a better understanding 05:27.390 --> 05:29.340 of what run over here is doing, 05:29.340 --> 05:32.160 have a better understanding of what command is doing 05:32.160 --> 05:34.920 and kind of put this entire equation together. 05:34.920 --> 05:35.753 So, quick break. 05:35.753 --> 05:36.900 We're gonna come back to the next section 05:36.900 --> 05:38.970 and do a little bit more of a deep dive. 05:38.970 --> 05:40.670 So, I'll see you in just a minute.