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‫OK let's do some fun stuff. In this lecture,

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‫we're going to quickly talk about the difference between images and containers. Then we're going

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‫to jump right into playing around with a container. We're going to start it,

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‫we're going to stop and remove it, and do some common administrative functions. Then we're going to

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‫check out the container logs and the processes running in our container.

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‫So before we jump in real quick, it's good to know the difference between an image and a container. An

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‫image is the binaries and libraries and source code that all make up your application. The container

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‫is a running instance of that image.

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‫Now, you can have many containers all based off the same image. In this lecture,

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‫we're going to be using the Open Source Nginx web server. So we'll be starting our containers

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‫based off that Nginx image. We get all of our images from registries. Registries are kind of like

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‫what GitHub is to source code. Image registries are for container images and the default one for Docker

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‫is Docker Hub, which you can check out at

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‫hub.docker.com.

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‫We'll play more with that later.

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‫But for now be aware that these two things are quite different, and in the next section we're going to

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‫jump in to images.

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‫But for now let's focus on containers.

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‫OK now we're going to start a new container and use some Docker commands to manage that container.

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‫docker container run

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‫publish 80:80 nginx.

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‫Don't worry if you don't know what all that means. We'll go through it all in a minute.

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‫I'll hit enter...

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‫switch over to my browser, and type in localhost.

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‫There we go.

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‫Our Nginx server is listening. I can hit refresh several times and you'll see the log entries

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‫happening in our command line here.

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‫Now what did we just do? In the background,

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‫the Docker engine actually looked for an image called nginx, and it pulled down the latest image for

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‫nginx from Docker Hub. Then it started it as a new process in a new container for us to use.

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‫The published part of the command exposes my local port 80 on my local machine and sends all traffic

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‫from it to the executable running inside that container on port 80.

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‫And since Nginx is a web server it's going to default to port 80 and the traffic just forwards automatically

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‫through my browser to my local host and into that container.

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‫But we don't always want this thing running in the foreground inside of our command line.

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‫So let's hit Control c and I'm going to hit the Up Arrow and I'm going to back up a little bit and type in

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‫detach.

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‫Now detach tells Docker to run it in the background.

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‫And we get back the unique container ID of our container.

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‫And every time you run a new container you get a new unique ID.

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‫So if we go back over to our browser and hit refresh a couple of times you can see that it's still running.

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‫So let's do a command to list our containers. docker container

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‫ls

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‫And you'll see the one that's still running here.

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‫It's matching the container ID of the command we just ran. You'll see the container still running

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‫that we just started.

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‫So let's stop that container real quick.

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‫docker container stop. Then the container ID. For the container ID I only have to type the first

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‫few digits, enough for it to be unique, and I stopped it.

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‫Now if I do a docker container ls, you'll notice nothing shows up.

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‫So the ls command only shows by default running containers.

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‫If I do an ls -a, I get back two. Now, why do I get two?

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‫When we ran each time the docker container run command, it started a new container from that Nginx

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‫image. You'll notice on the right here that there's these random names. We didn't use these.

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‫How did we get these?

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‫So the container ID is always created for us.

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‫And the name is also required to be unique.

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‫And if we don't specify it, it will be created for us. We can always name something ourselves,

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‫but if we let it pick its own, it's actually an interesting little bit of history around Docker is that

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‫they've had this for years now that that name will randomly be generated from an open source list

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‫of adjectives and the surnames of notable hackers or scientists.

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‫And it's pretty funny sometimes you'll get some really peculiar names in there.

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‫So let's create a new one. docker container run.  Put in our publish

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‫and our detach.

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‫But this time we're going to specify a name. I'm going to call it webhost nginx.

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‫And now if I do my docker container ls -a you'll see three containers.

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‫The one we just started. It has a name of webhost and then the two that we previously started and

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‫then stopped.

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‫Since we're not running this in the foreground anymore, we can't see the logs.

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‫So let's go back to our browser and I'm going to hit refresh a couple of times to generate some logs.

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‫Then back to our terminal and I'll do docker container logs webhost. And it will spit out the latest

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‫logs in the webhost.

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‫There's a couple of options you want to play around with on the logs command to have it follow the

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‫logs automatically or it can just capture the last few log events so that you don't end up with the

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‫entire log file being dumped to your screen.

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‫We can also use some other docker container commands to check on that running container. We can

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‫try docker container top. You can see the help there.

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‫That lets us know we need to specify container name webhost. You can see this is the process running

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‫inside the container.

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‫Now for Nginx we don't need to necessarily know all this but it's just interesting to note that with

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‫Nginx,

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‫there's actually a master process and then it spawns worker processes based on the configuration.

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‫Again we can always type docker container and --help to get a list of all the commands we

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‫could try on that container.

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‫Now let's clean up what we just did.

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‫So let's do a docker container.

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‫ls -a, and that's going to list all three of my containers.

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‫Now, I'm actually going to remove all three at the same time.

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‫Sometimes subcommands of Docker can actually take multiple values.

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‫So in this case I can do a docker container rm and then I can actually specify 63f 690 and ode.

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‫whoops 0de.

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‫So I got an error. What just happened here?

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‫All right. The first two were safely deleted.

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‫The third one it's telling me I can't remove a running container because it's a safety measure.

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‫It makes sure that you don't accidentally remove the actual process that's still running. If you do

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‫a docker container ls you'll see we still have one running.

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‫Now I could actually do a docker container stop to stop it first and then remove it.

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‫But I'm actually going to do a docker container rm -f for force and 63f. And there we go.

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‫Now if I do a docker container ls -a you'll see that nothing's there.

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‫So now we've cleaned up our mess.

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‫OK.

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‫So in just a matter of minutes we were able to use a single command to download and run an Nginx

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‫web server with a default configuration listening on port 80 and then we were able to create several

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‫of those, play with the logs and then remove the containers to clean up what we had done.