Dockerfile is a text file that contains a set of instructions for building a Docker image. Docker images are used to create Docker containers, which are lightweight and portable runtime environments for applications. Dockerfile provides developers with an easy and efficient way to define the environment and dependencies required for an application to run in a Docker container.
The Dockerfile starts with the base image, which is the image on top of which the application image will be built. The base image provides the operating system and other dependencies required for the application to run. The base image can be any pre-built image available on Docker Hub, or a custom image built by the user.Next, the Dockerfile defines the instructions to install the application and its dependencies. This typically involves installing packages and libraries required by the application. Additionally, the Dockerfile can define environment variables that configure the application at runtime.
FROM node:13.12.0-alpine
#This line specifies the base image for the Docker image, which is the official Node.js 13.12.0-alpine image. This image is a minimalistic version of Alpine Linux with Node.js pre-installed.
WORKDIR /app
#This line sets the working directory inside the Docker container to /app. This is where the application code and dependencies will be stored.
ENV PATH /app/node_modules/.bin:$PATH
#This line sets an environment variable to include the node_modules/.bin directory in the container's PATH environment variable. This allows us to use locally installed Node.js modules from the command line.
COPY package.json ./
COPY package-lock.json ./
#These lines copy the package.json and package-lock.json files from the host machine into the Docker image's /app directory.
RUN npm install --silent
#This line runs the npm install command inside the Docker container to install the dependencies specified in the package.json file.
RUN npm install react-scripts@4.0.3 -g --silent
#This line installs the global package react-scripts version 4.0.3 silently. This package is required to run the application and is specified in the package.json file.
COPY . ./
#This line copies the entire application code from the host machine into the Docker image's /app directory.
EXPOSE 8000
#This line exposes port 8000 for the Docker container
CMD ["npm", "start", "0.0.0.0:8000"]
# It runs the npm start command with the parameter 0.0.0.0:8000