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Using these utility containers

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as we did it here works.

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But as I mentioned, it can be cumbersome to write

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these long commands, especially with the bind mounts.

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Good news is, we can also use Docker Compose for that

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even though it's just one container.

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But I did mention that Docker Compose

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can also be helpful for just one container.

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And maybe you also have projects with multiple containers,

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some app containers, some utility containers,

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you can mix and match that,

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and you will see all of that in action in a bigger setup

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and a bigger project right after this module.

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when we dive into Level.

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And there we'll set up a Level application

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and also use some utility containers.

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But, step-by-step, how can we use Compose here?

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Well, as always, we have to add

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a docker dash compose dot yaml file,

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and in there we define our services as you learned it.

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So we started with the version

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which is 3.8 for me here,

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and then I add my services key.

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And here I have only one service and I will name it npm.

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And this will be a container which should use node

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and which should den also give me

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this entry point and so on.

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So I will use this Docker file here,

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and hence in the npm service,

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we can use to build command and simply use dot slash

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to indicate that we're already in the folder

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in which this Docker file can be found for this container.

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So this now tells compose that this image should be built

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when this container is being used.

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Now, the cool thing is, we can also now add

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this standard input open flag and the tdy flag

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to set both to true,

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to ensure that if the command needs our input,

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we can provide that input.

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And we can also now add our volumes here,

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and then add our bind mount by connecting the folder

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in which this docker compose dot yaml file is,

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to the app folder inside of the container, just like this.

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And that's essentially the command we executed before

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now moved into a docker compose yaml file.

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And there it's easier to maintain,

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and we don't have to rewrite it all the time.

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So now instead, we can simply use this docker compose file.

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And we learned that we can use up

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to bring up this container.

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Now, if I just run up like this however,

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it in the end does something strange.

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It starts building npm,

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and I don't know what it's doing there.

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The problem here is that now I executed just npm,

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because I have just npm as a entry point,

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and I didn't specify any other command.

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So instead we can use docker compose up

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and then maybe also add a comment thereafter, maybe init.

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But if I do that, that fails, no such service init.

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And indeed, we use Docker Compose

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differently than just a docker run command.

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Docker compose up is really meant to bring up

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services defined in a docker compose yaml file.

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And here we're typically talking

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about application containers,

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so containers that are started

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and then should continue running.

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For these utility containers,

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we also got to command though.

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We get docker composed exec to run commands

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in already running containers

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which were created by Docker Compose,

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but we also got docker compose run,

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and that's now a useful command here.

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Docker compose run allows us to run as single service

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from this yaml file in case we had multiple services,

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here we have only one, but if we had multiple services,

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we could also target a single service by the service name.

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So in this case, npm, because I used npm up here,

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I use npm down there.

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And then, with any command that should be upended

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after our entry point of our choice,

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so for example, init.

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And now if I hit Enter,

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I'm getting all these questions again,

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and then it finishes and creates this project for me.

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And that's even better to see if I delete node modules

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and the package JSON files, and I run this again.

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So let's run it again.

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Let's quickly go through all these questions,

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confirmed this, and here we are.

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There's our package JSON file again.

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So now we use docker compose for that,

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with the docker compose run command.

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Now one important word about that though,

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if you inspect your running containers,

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you'll see no containers, but if you inspect all containers,

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you see a lot of containers here.

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And the reason for that is, that I never added

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the dash dash rm flag when I used docker run,

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and of course we could do that there.

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But for Docker compose we have something similar.

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When we start services with docker compose up,

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they are automatically deleted,

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so the containers are automatically removed if we use down.

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But with docker compose run, there is no up and down,

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a container starts, does its thing,

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and once the command finished, it shuts down.

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But with run, it's not removed automatically.

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You can change that though by not just using run like this,

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but by also adding dash dash rm here,

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and then this utility container will be removed

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once to command finish.

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So with that can still execute the command,

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but thereafter this container is gone.

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Of course for the moment we can clean up

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all the containers we have with docker container prune,

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and this will also remove all the unused containers.

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But I find it quite important to be aware

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of this dash dash rm flag on docker compose run,

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because that makes sure that you don't end up

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with all those unnecessary containers in the first place.

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And that's it, these are utility containers

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as I'd like to call them.