Docker – File Instructions

Docker File Instructions

Dockerfile is a script that contains instructions for building a Docker image. Here are some common instructions used in Dockerfile:

FROM: specifies the base image to use for the build process.
RUN: executes a command in the container. This command is executed during the build process.
COPY/ADD: copies files or directories from the host machine to the container.
WORKDIR: sets the working directory for the rest of the instructions in the Dockerfile.
ENV: sets an environment variable in the container.
EXPOSE: specifies the port(s) that the container will listen on at runtime.
CMD/ENTRYPOINT: specifies the command to run when the container starts.

Here is an example Dockerfile that uses some of these instructions:

# Use the official Node.js image as the base image 
FROM node:14 
# Set the working directory to /app 
WORKDIR /app 
# Copy the package.json and package-lock.json files to the container 
COPY package*.json ./ 
# Install the dependencies 
RUN npm install 
# Copy the rest of the application files to the container 
COPY . . 
# Expose port 3000 
EXPOSE 3000 
# Start the application when the container starts CMD 
[ "npm", "start" ]

Dockerfile uses Node.js as the base image, sets working directory to /app, copies package.json, package-lock.json, installs the dependencies, copies the rest of the application files, exposes port 3000, and starts the application when the container starts.