The relationship between Dockerfile and . and how to build automated mirroring

The relationship between Dockerfile and . and the construction of automated images

With the development of containerization technology, Docker has become a widely used container engine.

The core of Docker is the image, and building Docker images requires the use of Docker file.

In GitLab CI/CD Pipeline, we usually need to build and deploy applications automatically, and many times we use Docker images to do this.

So, how do you call Dockerfile and build an automated image in Pipeline?

First, we need to understand the relationship between Dockerfile and . Dockerfile is used to define how to build a Docker image file. It contains a series of instructions and parameters that allow the Docker engine to perform corresponding operations, such as installing software, copying files, etc.

The . file is used to define GitLab CI/CD Pipeline, which can contain the stages for building Docker images. If you add the stage to build a Docker image in the . file, then the image will be built through the Dockerfile.

See an example of a Java project

Suppose we have a Java project called my-app, and its directory structure is as follows:

my-app/
    Dockerfile
    .
    src/
        main/
            java/
                com/
                    mycompany/
                        

Then, we can use the following . file to define Pipeline:

yaml
image: docker:latest

stages:
  - build
  - deploy

build:
  stage: build
  script:
    - docker build -t my-app:latest . # Build images using Dockerfile
deploy:
  stage: deploy
  script:
    - docker run --rm -it -p 8080:8080 my-app:latest # Start the container and run the application

In the above example, we define two stages, namely build and deploy.

In the build stage, we call Dockerfile through the docker build command to build my-app image.

In the deploy stage, we start the my-app image through the docker run command and map it to the host's port 8080.

See an example of a Go project

Suppose we have a Go project called go-app, and its Dockerfile is as follows:

dockerfile
FROM golang:1.15-alpine as builder
WORKDIR /app
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .

FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /app
COPY --from=builder /app/main .
EXPOSE 8080
CMD ["./main"]

In this Dockerfile, we first start building from the golang:1.15-alpine basic image, compile it in it, and generate an executable file named main.

Next, we start building with the alpine:latest base image and add the required packages to it.

Finally, we copy the previously generated executable file into the container and expose port 8080.

Then, in the . file, we can call the Dockerfile and build the automated image using the following method:

yaml
image: docker:latest

stages:
  - build
  - deploy

build:
  stage: build
  script:
    - docker build -t go-app:latest . # Use Dockerfile to build go-app images
deploy:
  stage: deploy
  script:
    - docker run --rm -it -p 8080:8080 go-app:latest # Start the container and run the application

In the above example, we also define two stages, namely build and deploy.

In the build stage, we call Dockerfile through the docker build command to build the go-app image.

In the deploy stage, we start the go-app image through the docker run command and map it to the host's port 8080.

To sum up

Dockerfile and . files are two key components in building automated images in GitLab CI/CD Pipeline.

Dockerfile defines the specific way of building Docker images, and the file contains the Pipeline stage, where Dockerfile can be called to build images and implement automated deployment.

Using these two files, we can quickly and reliably build and deploy applications and provide a better collaboration environment for development teams.

The above is personal experience. I hope you can give you a reference and I hope you can support me more.