WEBVTT 00:00.720 --> 00:01.553 -: In the last section 00:01.553 --> 00:03.420 we ran the Docker PS command 00:03.420 --> 00:04.890 and we saw one variation of it, 00:04.890 --> 00:09.240 which was Docker PS dash, dash all. 00:09.240 --> 00:11.190 When we ran dash dash all on here, 00:11.190 --> 00:12.630 we saw that we got a print-up 00:12.630 --> 00:13.650 of all the containers 00:13.650 --> 00:15.660 we'd ever started up on our machine, 00:15.660 --> 00:17.100 which was kind of interesting 00:17.100 --> 00:18.337 'cause it kind of begs the question 00:18.337 --> 00:21.870 "When does a container like really get shut down? 00:21.870 --> 00:23.400 Why does it get shut down?" 00:23.400 --> 00:25.650 And "what happens when it gets shut down?" 00:25.650 --> 00:26.820 So starting this section, 00:26.820 --> 00:29.670 I wanna start to show you a little bit around the life cycle 00:29.670 --> 00:32.220 of a container, which is gonna give you a better idea 00:32.220 --> 00:34.230 of what's going on behind the scenes. 00:34.230 --> 00:36.060 Now, before first investigating 00:36.060 --> 00:37.260 or just jumping to the end, 00:37.260 --> 00:38.880 like figuring out what happens 00:38.880 --> 00:40.410 when a container gets shut down. 00:40.410 --> 00:41.520 I want to kind of go all the way 00:41.520 --> 00:43.110 to the start and really figure out 00:43.110 --> 00:46.650 what happens when a container is first created. 00:46.650 --> 00:48.090 Now we've learned at this point 00:48.090 --> 00:50.520 that to start up a new container from an image 00:50.520 --> 00:52.680 we use the Docker run command. 00:52.680 --> 00:54.570 But when we looked at this diagram, 00:54.570 --> 00:56.010 remember we looked at this diagram 00:56.010 --> 00:57.630 like two or three sections ago. 00:57.630 --> 00:58.463 You'll notice 00:58.463 --> 01:00.900 that I had put some very particular terminology here. 01:00.900 --> 01:05.070 I said creating and running a container. 01:05.070 --> 01:07.470 Creating a container, and actually starting it up, 01:07.470 --> 01:10.143 are actually two separate processes. 01:11.550 --> 01:13.860 So there's actually two additional commands 01:13.860 --> 01:15.390 in addition to Docker run 01:15.390 --> 01:18.351 that we can use to start up a new container. 01:18.351 --> 01:19.860 Docker run. 01:19.860 --> 01:21.360 Running that at your command line 01:21.360 --> 01:25.590 is identical to running two other commands together. 01:25.590 --> 01:28.800 First Docker create and then Docker start. 01:28.800 --> 01:29.820 As you might guess, 01:29.820 --> 01:33.030 the Docker create commands is used to create a container 01:33.030 --> 01:34.320 out of an image 01:34.320 --> 01:37.410 and then start is used to actually start an image. 01:37.410 --> 01:39.157 But at this point you might be a little bit curious of, 01:39.157 --> 01:42.030 "Hey, what's the distinction between creating a container 01:42.030 --> 01:43.890 and actually starting a container?" 01:43.890 --> 01:45.210 Let's look at a diagram that's gonna help you 01:45.210 --> 01:47.670 understand the differences between the two. 01:47.670 --> 01:50.400 So we've looked at a diagram like this several times before. 01:50.400 --> 01:52.050 Remember on our image over here 01:52.050 --> 01:54.840 we've got that kind of file-system snapshot of sorts 01:54.840 --> 01:56.763 and we've also got a startup command. 01:57.930 --> 02:00.540 The process of creating a container 02:00.540 --> 02:03.120 is where we kind of take the file system in here 02:03.120 --> 02:07.080 and kind of prep it for use in this new container. 02:07.080 --> 02:08.490 When we create the container, 02:08.490 --> 02:10.710 we're just talking about kind of prepping 02:10.710 --> 02:13.740 or setting-up this file-system snapshot to be used 02:13.740 --> 02:15.540 to create the container. 02:15.540 --> 02:17.490 To actually start the container, 02:17.490 --> 02:20.460 that's when we actually execute this startup command 02:20.460 --> 02:23.370 that might start up the process of like "Hello world". 02:23.370 --> 02:25.740 Or in the case of that BusyBox one that we used 02:25.740 --> 02:27.450 the echo "high there" 02:27.450 --> 02:29.580 or whatever process is supposed to be executed 02:29.580 --> 02:31.020 inside the container. 02:31.020 --> 02:32.670 So again, creating a container 02:32.670 --> 02:34.620 is about the file system. 02:34.620 --> 02:38.700 Starting it is about actually executing the startup command. 02:38.700 --> 02:39.540 So with that mind, 02:39.540 --> 02:42.120 let's try flipping over to our command line really quickly 02:42.120 --> 02:44.010 and we're gonna start to investigate the differences 02:44.010 --> 02:46.833 between creating a container and starting a container. 02:48.270 --> 02:50.010 Over at my command line 02:50.010 --> 02:53.730 I'm gonna first try running the Docker create 02:53.730 --> 02:56.850 and start commands with the "hello world" image. 02:56.850 --> 03:01.850 So I will first do Docker create "Hello" dash "world". 03:02.880 --> 03:03.930 When I run that command 03:03.930 --> 03:06.660 I get this long string of characters printed out. 03:06.660 --> 03:10.860 This is the ID of the container that was just created. 03:10.860 --> 03:13.980 I can now actually execute the "hello world" command 03:13.980 --> 03:18.420 inside of this container by running Docker start. 03:18.420 --> 03:20.727 And then I'm gonna add on a little argument here. 03:20.727 --> 03:22.350 I'm gonna say dash a, 03:22.350 --> 03:24.420 we'll talk about what that is in just a second, 03:24.420 --> 03:26.730 and then I'm gonna paste the ID 03:26.730 --> 03:28.170 that was just emitted right here. 03:28.170 --> 03:31.500 So I'm gonna paste in that really long series of characters 03:31.500 --> 03:33.120 and then when I run this command 03:33.120 --> 03:36.360 we'll see that familiar welcome message up here. 03:36.360 --> 03:37.380 So what happened here? 03:37.380 --> 03:38.910 Well again, first off, 03:38.910 --> 03:40.200 we kind of prepped the container 03:40.200 --> 03:42.450 by getting that file system ready. 03:42.450 --> 03:44.640 Then after that we actually executed 03:44.640 --> 03:48.270 the primary startup command in there with Docker start. 03:48.270 --> 03:50.160 Now, what was with the dash A right there? 03:50.160 --> 03:51.900 Well, to show you what's going on with that 03:51.900 --> 03:54.000 let's try running Docker start again 03:54.000 --> 03:55.563 but without the dash A. 03:57.210 --> 03:58.890 So I'm gonna run Docker start 03:58.890 --> 04:01.380 and then I'm going to again paste in. 04:01.380 --> 04:02.220 Oops, I lost the thing. 04:02.220 --> 04:05.013 I gotta do the create again very quickly. 04:07.230 --> 04:09.840 So there's my ID and I'll do Docker start 04:09.840 --> 04:11.643 but without the dash A this time. 04:12.540 --> 04:14.100 So when I run Docker start, 04:14.100 --> 04:16.650 you'll notice that I just see the ID. 04:16.650 --> 04:18.090 The dash A command 04:18.090 --> 04:19.560 is what's going to make Docker 04:19.560 --> 04:22.290 actually watch for output from the container 04:22.290 --> 04:24.360 and print it out to your terminal. 04:24.360 --> 04:26.670 So the dash a specifically means "hey 04:26.670 --> 04:28.721 kind of attached to the container", so to speak 04:28.721 --> 04:31.410 and "watch for output coming from it and print 04:31.410 --> 04:33.720 it out at my terminal". 04:33.720 --> 04:36.300 So when I put on Docker start dash a, that means 04:36.300 --> 04:39.060 give "me any output that is coming from that thing". 04:39.060 --> 04:41.250 And when I run that, boom, there it is. 04:41.250 --> 04:43.230 So you'll notice that's a very small difference 04:43.230 --> 04:45.810 between Docker run and Docker start. 04:45.810 --> 04:46.643 By default, 04:46.643 --> 04:48.960 Docker run is going to show you all the logs 04:48.960 --> 04:51.300 or all the information coming outta the container. 04:51.300 --> 04:53.490 By default, Docker start is the opposite. 04:53.490 --> 04:55.050 Docker start is not gonna show you 04:55.050 --> 04:56.950 information coming outta the terminal. 04:58.440 --> 04:59.273 All right. 04:59.273 --> 05:01.500 So that's the differences between Docker run 05:01.500 --> 05:04.170 and Docker start and Docker create. 05:04.170 --> 05:05.490 Let's take a quick pause right here. 05:05.490 --> 05:06.720 We're gonna come back to the next section 05:06.720 --> 05:08.340 and we'll talk a little bit more about 05:08.340 --> 05:09.810 exactly what it meant 05:09.810 --> 05:13.890 when we saw with the Docker PS All that exited status. 05:13.890 --> 05:16.340 So quick break and I'll see you in just a minute.