KodeKloud Notes

In this tutorial, you’ll learn how to build a lightweight, custom Docker image for an HTTPD (Apache) web server on CentOS 7. We’ll cover:

Setting up the build context
Crafting an optimized Dockerfile
Adding a simple index.html
Building, testing, and pushing your image to Docker Hub

By following these steps, you’ll gain hands-on experience with multi-layered Docker images and best practices for containerized web servers.

1. Prepare the Build Context

First, create an isolated directory for all build artifacts. This ensures that nothing outside the folder is accidentally added to your image.

cd /tmp
mkdir firstimage && cd firstimage
ls -1
# (should be empty)

Build Context

Everything in this directory (including subdirectories) is sent to the Docker daemon during the build. Keep it lean to speed up image creation.

2. Write the Dockerfile

Create a file named Dockerfile:

vi Dockerfile

Populate it with the following content:

# Base image: CentOS 7
FROM centos:7

# 1. Update and install HTTPD
RUN yum -y update && \
    yum -y install httpd

# 2. Copy a custom HTML page into the default document root
COPY index.html /var/www/html/index.html

# 3. Expose port 80 for HTTP traffic
EXPOSE 80

# 4. Start HTTPD in the foreground
CMD ["httpd", "-D", "FOREGROUND"]

Instruction	Description
FROM	Specifies the base image (CentOS 7)
RUN	Runs commands in a new layer
COPY	Copies files from build context
EXPOSE	Documents the port on which the container listens
CMD	Defines the default command at container start

Security Reminder

Running containers as root can pose risks. For production workloads, consider adding a non-root user and switching with USER.

For more details on Dockerfile syntax, see the Dockerfile reference.

3. Create the HTML Page

Add a simple index.html in the same directory:

vi index.html

Example content:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Welcome</title>
</head>
<body>
  <h1>Hello from KodeKloud Again</h1>
</body>
</html>

Verify both files are present:

ls -l
# total 8
# -rw-r--r-- 1 root root 199 May  4 13:38 Dockerfile
# -rw-r--r-- 1 root root  98 May  4 13:39 index.html

4. Build the Docker Image

Use a clear, versioned tag for your image:

docker image build -t yogeshraheja/kodekloud-web-image:v1 .

You should see output for each of the five build steps. Once complete, confirm the image exists:

docker image ls

Inspect the image layers:

docker image history yogeshraheja/kodekloud-web-image:v1

5. Test the Container

Run a container, mapping host port 82 to container port 80:

docker container run -d \
  -p 82:80 \
  --name httpd-test \
  yogeshraheja/kodekloud-web-image:v1

Open your browser to http://<host_ip>:82. You should see your custom page:

The image shows a web browser displaying a page with the text "Hello from KodeKloud Again" on a plain white background. The URL in the address bar is "52.90.207.2:82".

6. Push to Docker Hub

Authenticate and push your image so others can pull it:

docker login
docker push yogeshraheja/kodekloud-web-image:v1

Verify on Docker Hub that your repository is public and the tag is available.

Quick Command Reference

Command	Purpose
docker image build -t user/repo:tag .	Build an image with a tag from the current directory
docker container run -d -p host_port:container_port --name name image	Run a container detached with port mapping
docker image ls	List all local images
docker image history image_name:tag	Show the history of image layers
docker push user/repo:tag	Push a local image to Docker Hub

Links and References

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