How to build docker images with Dockerfile • Shipan Jodder

A Dockerfile is a script containing a set of instructions to automate the building of Docker images. It defines everything required to set up a containerized environment.

Basic Structure of a Dockerfile

A Dockerfile typically includes:

Command	Description
`FROM`	Specifies the base image (e.g., ubuntu, nginx, node)
`LABEL`	Metadata like maintainer information
`RUN`	Runs commands during image build (e.g., install packages)
`WORKDIR`	Copies files from the host to the container
`COPY`	Specifies the base image (e.g., ubuntu, nginx, node)
`ADD`	Like COPY, but also supports URLs and tar extraction
`ENV`	Sets environment variables inside the container
`EXPOSE`	Defines which ports the container will listen on
`CMD`	Default command executed when the container starts
`ENTRYPOINT`	Similar to CMD, but more flexible for argument handling

Example Dockerfile

# Step 1: Use an official base image
FROM ubuntu:latest

# Step 2: Set the maintainer label
LABEL maintainer="your-email@example.com"

# Step 3: Install required packages
RUN apt-get update && apt-get install -y curl vim

# Step 4: Set the working directory
WORKDIR /app

# Step 5: Copy files into the container
COPY myscript.sh /app/myscript.sh

# Step 6: Set environment variables
ENV MY_ENV_VAR=production

# Step 7: Expose a port
EXPOSE 8080

# Step 8: Default command to run the container
CMD ["bash", "myscript.sh"]

Building and Running a Dockerfile

After creating your Dockerfile, build an image and run it:

Build the Image

docker build -t my-image .

(-t assigns a tag to the image, . refers to the current directory)

Run a Container from the Image

docker run -d -p 8080:8080 --name my-container  my-image