WEBVTT 00:01.110 --> 00:02.190 Instructor: We're now successfully able 00:02.190 --> 00:04.530 to visit our running web application inside the browser. 00:04.530 --> 00:07.470 But there's one last little thing that I wanna point out. 00:07.470 --> 00:09.750 I'm gonna start my container up using the image 00:09.750 --> 00:11.550 that we've already built, but this time 00:11.550 --> 00:13.950 I'm gonna start up a shell inside the container, 00:13.950 --> 00:17.160 so that we can do a little bit of debugging inside there. 00:17.160 --> 00:18.720 Remember that we can start up a shell 00:18.720 --> 00:21.480 inside of most Alpine-based containers 00:21.480 --> 00:24.423 by running Docker run dash IT, 00:25.260 --> 00:27.030 and I'll put down my container name 00:27.030 --> 00:29.860 of Steven Grider simpleweb 00:30.840 --> 00:33.960 and then I will override the default startup command 00:33.960 --> 00:35.040 with sh. 00:35.040 --> 00:37.560 Remember, this is a reference to the Shell program. 00:37.560 --> 00:38.670 It will start up a shell 00:38.670 --> 00:42.330 that we can type commands into inside the container. 00:42.330 --> 00:43.163 Now you'll notice 00:43.163 --> 00:45.240 that I did not specify a port mapping here. 00:45.240 --> 00:46.080 It's because we are not 00:46.080 --> 00:47.580 going to actually start up the server. 00:47.580 --> 00:49.260 I just want to attempt to look 00:49.260 --> 00:51.933 at the files and folders inside the container. 00:53.010 --> 00:53.843 So I'll run that 00:53.843 --> 00:55.320 and then we'll get a command prompt, 00:55.320 --> 00:58.650 based inside of the root directory of the container. 00:58.650 --> 01:00.300 Now inside of here, I'm gonna print out 01:00.300 --> 01:03.363 all the available files and folders with ls. 01:04.740 --> 01:06.240 So inside of here, you'll notice 01:06.240 --> 01:08.490 that when we did that copy operation, 01:08.490 --> 01:10.920 we copied into the root directory 01:10.920 --> 01:12.990 or the root folder of the container. 01:12.990 --> 01:14.400 And so in this root directory, 01:14.400 --> 01:18.000 we can see the Dockerfile, a package lock dot JSON file, 01:18.000 --> 01:20.940 which is automatically generated by NPM, 01:20.940 --> 01:23.220 package dot JSON, index dot JS, 01:23.220 --> 01:24.960 and all of our install dependencies 01:24.960 --> 01:27.210 were placed into this node modules folder. 01:27.210 --> 01:28.860 And again, these were all placed 01:28.860 --> 01:32.790 into the root directory of this container. 01:32.790 --> 01:35.640 Now, this is definitely not the best practice, 01:35.640 --> 01:36.690 and the reason for that 01:36.690 --> 01:39.810 is that if we happen to have any files or folders 01:39.810 --> 01:42.420 that conflict with the default folder system, 01:42.420 --> 01:45.540 like if we have a folder called var or root or run 01:45.540 --> 01:48.780 or lib, super, super likely for us 01:48.780 --> 01:50.940 to have a folder called lib inside of our project, 01:50.940 --> 01:52.710 we might accidentally overwrite 01:52.710 --> 01:56.310 some existing files or folders inside of the container, 01:56.310 --> 01:58.680 which is definitely not ideal. 01:58.680 --> 02:01.320 So we're gonna make a little change to our Docker file 02:01.320 --> 02:03.240 and rather than copying everything 02:03.240 --> 02:05.910 directly into the root project directory, 02:05.910 --> 02:07.170 we're actually gonna copy everything 02:07.170 --> 02:10.320 into, kind of, a nested directory instead. 02:10.320 --> 02:11.820 Now, rather than just changing 02:11.820 --> 02:15.240 the copy command inside of our Docker file and saying, 02:15.240 --> 02:18.120 oh yeah, copy it into, like, some application folder 02:18.120 --> 02:19.230 or something like that, 02:19.230 --> 02:21.210 there's actually an instruction 02:21.210 --> 02:23.192 that we can use inside the Dockerfile 02:23.192 --> 02:24.960 that is specifically meant to address 02:24.960 --> 02:26.280 this whole issue right here, 02:26.280 --> 02:28.740 of accidentally overriding files or folders 02:28.740 --> 02:30.600 by copying into a root directory. 02:30.600 --> 02:33.093 So let's take a look at what the instruction is. 02:34.650 --> 02:38.700 So we can add the workdir or work directory instruction 02:38.700 --> 02:40.050 into the Dockerfile 02:40.050 --> 02:43.083 and then pass a reference to a folder to it. 02:44.100 --> 02:48.090 Then, any following commands or any following instructions 02:48.090 --> 02:49.500 that we add to our Docker file 02:49.500 --> 02:53.010 will be executed relative to this folder. 02:53.010 --> 02:56.280 So in other words, if we add the workdir and then a folder 02:56.280 --> 02:59.340 above the copy instruction right here, 02:59.340 --> 03:01.920 it will make sure that we only execute, 03:01.920 --> 03:02.760 or excuse me, it'll make sure 03:02.760 --> 03:04.740 that when we actually do the copy instruction 03:04.740 --> 03:07.530 it won't copy it into the root directory, 03:07.530 --> 03:10.080 It'll copy it into the directory that we have specified 03:10.080 --> 03:12.690 as the working directory instead. 03:12.690 --> 03:15.000 So let's try doing that right now. 03:15.000 --> 03:17.940 I'm gonna add in an instruction of workdir, 03:17.940 --> 03:19.260 and then we are going to use 03:19.260 --> 03:22.500 a folder of slash user slash app. 03:22.500 --> 03:25.560 So let's say slash user slash app. 03:25.560 --> 03:27.900 If this folder does not exist inside the container, 03:27.900 --> 03:30.090 it'll be automatically created for us. 03:30.090 --> 03:33.750 Now you might be curious as to why I'm using user slash app. 03:33.750 --> 03:36.360 Well, to be honest, in the Node.js world 03:36.360 --> 03:39.030 it doesn't make a tremendous difference 03:39.030 --> 03:40.710 where you put your application into 03:40.710 --> 03:42.750 in a Linux-based operating system. 03:42.750 --> 03:44.850 There definitely are places that you don't want to put it, 03:44.850 --> 03:46.260 but at the end of the day, 03:46.260 --> 03:49.020 the user folder is a safe place to put your application. 03:49.020 --> 03:51.000 It's specified as the location 03:51.000 --> 03:54.000 for all of user home directories. 03:54.000 --> 03:55.680 Essentially, it's an okay place 03:55.680 --> 03:57.270 for us to put our application. 03:57.270 --> 03:58.230 Now, as I say that, 03:58.230 --> 04:00.630 there's definitely a lot of Linux diehards out there 04:00.630 --> 04:02.130 who would probably disagree with me 04:02.130 --> 04:04.650 and they might say, oh no, you should put this into var 04:04.650 --> 04:07.320 or you should put it into the home directory instead. 04:07.320 --> 04:08.850 So there is some disagreement out there 04:08.850 --> 04:11.070 on where the best place is for your application, 04:11.070 --> 04:12.600 but I can just about guarantee you 04:12.600 --> 04:14.640 that if you put it into user slash app, 04:14.640 --> 04:16.473 you're probably gonna be okay. 04:17.940 --> 04:20.940 Okay, so now we've added in the workdir instruction. 04:20.940 --> 04:23.040 I'm now gonna save the Dockerfile 04:23.040 --> 04:24.870 and then we'll flip back over to our terminal. 04:24.870 --> 04:28.590 I'll exit the running container by typing in exit 04:28.590 --> 04:29.640 and then we're going to make sure 04:29.640 --> 04:31.860 that we first rebuild our container 04:31.860 --> 04:34.290 and then we'll try to relaunch it. 04:34.290 --> 04:38.820 So I'll do a rebuild with Docker build dot. 04:38.820 --> 04:40.200 Oh, let's not forget to tag it. 04:40.200 --> 04:42.600 So Docker build dash T, 04:42.600 --> 04:47.550 your docker ID slash simpleweb, and then a dot. 04:47.550 --> 04:48.383 There we go. 04:49.800 --> 04:51.300 So we're going to rebuild it. 04:51.300 --> 04:53.550 Now, one thing that you'll notice is really interesting 04:53.550 --> 04:56.280 because we made a change to an instruction 04:56.280 --> 04:58.920 above the copy and NPM install, 04:58.920 --> 05:02.700 everything after that instruction has to rerun from scratch, 05:02.700 --> 05:05.070 so we cannot use any cached versions. 05:05.070 --> 05:08.130 In other words, the NPM install command has to run again 05:08.130 --> 05:10.050 and reinstall all of our dependencies, 05:10.050 --> 05:13.173 'cause we cannot use the cached version of that step. 05:15.300 --> 05:16.470 So we got our output here. 05:16.470 --> 05:18.690 Let's try starting up our container again. 05:18.690 --> 05:20.640 I'll first start it up in normal mode 05:20.640 --> 05:22.950 and try to visit it inside my browser. 05:22.950 --> 05:27.300 So we'll do a docker run dash P, to set up a port mapping 05:27.300 --> 05:30.690 and we'll map 8080 to 8080. 05:30.690 --> 05:33.030 And then, the container that I want to run 05:33.030 --> 05:35.883 is Steve Grider slash simpleweb. 05:39.180 --> 05:43.830 So we'll run that and then I'll go back over to my browser. 05:43.830 --> 05:47.260 I'll try to visit localhost 8080 05:48.630 --> 05:50.160 and yep, it looks like we're good to go. 05:50.160 --> 05:52.080 I can refresh the page. 05:52.080 --> 05:55.110 And if we also try to start up a shell inside the container, 05:55.110 --> 05:57.180 we'll see that all of our project directories, 05:57.180 --> 05:58.560 or excuse me, all of our project files 05:58.560 --> 06:00.600 are no longer in the root directory. 06:00.600 --> 06:03.960 To do so, we can either rerun the Docker run command 06:03.960 --> 06:07.050 with the IT and SH attached to it 06:07.050 --> 06:09.570 or we can use that docker exec command. 06:09.570 --> 06:11.160 You'll recall we can use Docker exec 06:11.160 --> 06:14.760 to start up a second process inside of a running container. 06:14.760 --> 06:15.750 Let's try doing it that way, 06:15.750 --> 06:17.493 just for a little bit of variety. 06:18.600 --> 06:21.780 So I will open up a second terminal window. 06:21.780 --> 06:24.480 I'll get the ID of that running container 06:24.480 --> 06:26.430 by using Docker PS. 06:26.430 --> 06:28.530 So here's the ID right here 06:28.530 --> 06:30.360 and then we can attach to that container 06:30.360 --> 06:32.100 and start up a shell inside of it, 06:32.100 --> 06:37.100 by using Docker exec dash IT, the ID of the container 06:37.470 --> 06:39.960 and then the program that we want to run inside of it, 06:39.960 --> 06:42.000 which in this case is shell. 06:42.000 --> 06:43.470 Don't forget the IT, right here, 06:43.470 --> 06:46.950 is to attach standard in and a nice looking terminal 06:46.950 --> 06:48.350 to the shell that starts up. 06:49.410 --> 06:50.880 So I'll run that and you'll notice 06:50.880 --> 06:55.050 that we enter directly in to the user slash app folder 06:55.050 --> 06:58.470 because we had set up that working directory previously. 06:58.470 --> 07:00.330 That workdir instruction, right here, 07:00.330 --> 07:03.270 not only affects commands that are issued later on 07:03.270 --> 07:04.680 inside of our Docker file, 07:04.680 --> 07:07.350 it also affects commands that are executed 07:07.350 --> 07:08.910 inside the container later on 07:08.910 --> 07:10.653 through the Docker exec command. 07:12.240 --> 07:14.370 So if I now do an ls right here, 07:14.370 --> 07:16.650 I'll see all of my project files and folders 07:16.650 --> 07:19.380 nicely isolated inside of the single file. 07:19.380 --> 07:21.540 And I can change back to my root directory 07:21.540 --> 07:24.300 by doing CD forward slash, 07:24.300 --> 07:26.790 print out all the files and folders there with ls 07:26.790 --> 07:27.623 and I'll see 07:27.623 --> 07:30.540 that I do not have any possible conflicts going on. 07:30.540 --> 07:32.940 We have nicely spaced our application, 07:32.940 --> 07:34.890 or kind of, isolated our application 07:34.890 --> 07:37.170 into this folder right here. 07:37.170 --> 07:38.520 All right, so that's pretty much it. 07:38.520 --> 07:39.520 Looking pretty good. 07:40.500 --> 07:41.333 Now, believe it or not, 07:41.333 --> 07:44.490 there is one last little thing that I wanna look at. 07:44.490 --> 07:46.380 So let's do one more quick break 07:46.380 --> 07:48.150 and we'll come back in the next section 07:48.150 --> 07:50.610 and do one quick last little thing. 07:50.610 --> 07:52.260 So I'll see you in just a minute.