WEBVTT 00:00.750 --> 00:02.370 -: In the last section, we had a long discussion 00:02.370 --> 00:05.880 about the relationship between a container and an image. 00:05.880 --> 00:08.400 We had said that a container is a running process 00:08.400 --> 00:11.640 along with a subset of physical resources on your computer 00:11.640 --> 00:15.180 that are allocated to that process specifically. 00:15.180 --> 00:17.160 We also spoke a little bit about the relationship 00:17.160 --> 00:19.830 between an image and a running container. 00:19.830 --> 00:20.700 Remember, an image 00:20.700 --> 00:23.130 is really kind of a snapshot of the file system, 00:23.130 --> 00:26.400 along with a very specific startup command as well. 00:26.400 --> 00:29.190 Now, one thing that I wanna mention very quickly here, 00:29.190 --> 00:30.960 in the last section, we spoke a little bit 00:30.960 --> 00:33.870 about the separation or the kind of the isolation 00:33.870 --> 00:37.020 of these resources through a technique called namespacing. 00:37.020 --> 00:38.760 And we also said that we could limit 00:38.760 --> 00:40.080 the amount of resources used 00:40.080 --> 00:42.690 by these control group things as well. 00:42.690 --> 00:45.570 Now, this feature of namespacing and control groups 00:45.570 --> 00:48.870 is not included by default with all operating systems, 00:48.870 --> 00:50.070 even though in the last section, 00:50.070 --> 00:51.870 I had kind of specifically said like, 00:51.870 --> 00:54.870 oh yeah, your operating system has a kernel, too. 00:54.870 --> 00:57.480 These features of namespacing and control groups 00:57.480 --> 01:01.140 are specific to the Linux operating system. 01:01.140 --> 01:04.350 So namespacing control groups belong to Linux, 01:04.350 --> 01:06.990 not to Windows, not to macOS. 01:06.990 --> 01:09.210 So that might make you kind of question or wonder 01:09.210 --> 01:11.430 how are you running Docker right now? 01:11.430 --> 01:12.900 You know, we are running a Docker client 01:12.900 --> 01:14.760 and we are running Docker containers 01:14.760 --> 01:17.820 on a macOS or a Windows operating system. 01:17.820 --> 01:20.670 How is that happening if these are Linux-specific features? 01:20.670 --> 01:23.070 Well, here's what's happening behind the scenes. 01:23.940 --> 01:27.240 When you installed Docker for Windows or Docker for Mac 01:27.240 --> 01:30.030 just a moment ago in the last couple sections, 01:30.030 --> 01:33.510 you installed a Linux virtual machine. 01:33.510 --> 01:36.000 So, so long as Docker up here is running, 01:36.000 --> 01:38.430 you technically have a Linux virtual machine 01:38.430 --> 01:40.590 running on your computer. 01:40.590 --> 01:42.450 Inside of this virtual machine is 01:42.450 --> 01:45.150 where all of these containers are going to be created. 01:45.150 --> 01:48.270 So inside the virtual machine, we have a Linux kernel, 01:48.270 --> 01:50.220 and that Linux kernel is going to be 01:50.220 --> 01:53.430 hosting, running processes inside of containers. 01:53.430 --> 01:54.870 And it's that Linux kernel 01:54.870 --> 01:57.240 that's going to be in charge of limiting access 01:57.240 --> 02:00.360 or kind of constraining access or isolating access 02:00.360 --> 02:03.300 to different hardware resources on your computer. 02:03.300 --> 02:04.530 You can actually kind of see 02:04.530 --> 02:06.870 this Linux virtual machine in practice 02:06.870 --> 02:08.430 by opening up your terminal right now. 02:08.430 --> 02:11.100 And if you run that Docker version command again 02:11.100 --> 02:12.450 and look at your server, 02:12.450 --> 02:15.570 you'll notice that there's actually an OS entry on here 02:15.570 --> 02:16.403 and you'll notice 02:16.403 --> 02:19.590 that it probably doesn't have your operating system listed. 02:19.590 --> 02:22.320 Mine, for example, right here says very specifically Linux 02:22.320 --> 02:24.150 as the operating system. 02:24.150 --> 02:26.010 So that is kind of specifying 02:26.010 --> 02:27.900 that I'm running a Linux virtual machine 02:27.900 --> 02:29.190 and that's what's being used 02:29.190 --> 02:30.930 to host all these different containers 02:30.930 --> 02:33.360 that you and I are going to be working with. 02:33.360 --> 02:35.460 So just a little bit of interesting trivia. 02:35.460 --> 02:37.020 Now let's take another quick break right here. 02:37.020 --> 02:38.250 We're gonna continue the next section 02:38.250 --> 02:41.880 and start digging into the Docker client a little bit more. 02:41.880 --> 02:44.303 So quick break and I'll see you in just a minute.