# Working with Dockerfiles (.NET, Golang, Python, NodeJS)

## Three Problems for docker beginner

1. Programmer need be able to navigate through windows/mac/linux OS using cmd line fluently:
   1. `ls/dir` for list files
   2. `cd` for move through file systems
2. Working Directories
   1. Show current working directory `echo $PWD`
   2. Don't hardcode path to file in docker files
3. Understand *docker volume* `docker run -v hostPath:containerPath`
   1. e.g. `docker run -it -v $PWD:/work -w /work alpine:3.9 /bin/sh`

## dockerfile

Before bring up docker container, we need first create `dockerfile` to describe the image that we want to use to create containers.

For different languages, `c#`, `golang` & `python` each has a separate dockerfile. Each describe the complete environment can be used to develop corresponding programs 

## Docker compose

`Compose` is an **orchestration** tool that used to spinning up multi-container distributed applications, it shipped with Docker by default. It's not ideal for large system setup, but great for development purpose and testing

It's easy to define a multi-container app and accompanying services using **one single file**, and start it using single command. We can also build/push images to registry using `docker-compose`

The compose file is `docker-compose.yaml` in PWD

* Build image individually: `docker-compose build <service_name>`
* Build all images: `docker-compose build`

### Create & Push images built from docker-compose

1. Create image using `docker-compose.yaml` & `Dockerfile`
   1. Write `Dockerfile` and `docker-compose.yaml`
   2. Create image: `docker-compose build first-public-dockerhub-image` where
      1. `first-public-dockerhub-image` is the service name of the image
2. Login Docker hub
   1. `docker login`, without specify server address, it automatically connect to DockerHub
   2. Enter Username & Password
   3. Now computer has login DockerHub successfully
3. Go to Docker hub, create the `first-public-dockerhub-image` repository
4. Go to command line, push the image `docker push cruxligh/first-public-dockerhub-image`

References:
1. How to register a dockerhub registry: [Docker Hub QuickStart](https://docs.docker.com/docker-hub/)