docker-images

Using Third Party Images

Third-party images are pre-built Docker container images that are available on Docker Hub or other container registries. These images are created and maintained by individuals or organizations and can be used as a starting point for your containerized applications.

Finding Third-Party Images

Docker Hub is the largest and most popular container image registry containing both official and community-maintained images. You can search for images based on the name or the technology you want to use.

For example: If you’re looking for a Node.js image, you can search for “node” on Docker Hub and you’ll find the official Node.js image along with many other community-maintained images.

Using an Image in Your Dockerfile

To use a third-party image in your Dockerfile, simply set the image name as the base image using the FROM directive. Here’s an example using the official Node.js image:

FROM node:14

# The rest of your Dockerfile...

Be Aware of Security Concerns

Keep in mind that third-party images can potentially have security vulnerabilities or misconfigurations. Always verify the source of the image and check its reputation before using it in production. Prefer using official images or well-maintained community images.

Maintaining Your Images

When using third-party images, it’s essential to keep them updated to incorporate the latest security updates and dependency changes. Regularly check for updates in your base images and rebuild your application containers accordingly.

Building Container Images

Container images are executable packages that include everything required to run an application: code, runtime, system tools, libraries, and settings. By building custom images, you can deploy applications seamlessly with all their dependencies on any Docker-supported platform.

Dockerfile

The key component in building a container image is the Dockerfile. It is essentially a script containing instructions on how to assemble a Docker image. Each instruction in the Dockerfile creates a new layer in the image, making it easier to track changes and minimize the image size. Here’s a simple example of a Dockerfile:

# Use an official Python runtime as a parent image
FROM python:3.7-slim

# Set the working directory to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World

# Run app.py when the container launches
CMD ["python", "app.py"]

Building an Image

Once you have created the Dockerfile, you can build the image using the docker build command. Execute the following command in the terminal from the directory containing the Dockerfile:

docker build -t your-image-name .

This command tells Docker to build an image using the Dockerfile in the current directory (.), and assign it a name (-t your-image-name).

Inspecting Images and Layers

After a successful build, you can inspect the created image using docker image command:

docker image ls

To take a closer look at the individual layers of an image, use the docker history command:

docker history your-image-name

To view the layers of an image, you can also use the docker inspect command:

docker inspect your-image-name

To remove an image, use the docker image rm command:

docker image rm your-image-name

Pushing Images to a Registry

Once your image is built, you can push it to a container registry (e.g., Docker Hub, Google Container Registry, etc.) to easily distribute and deploy your application. First, log in to the registry using your credentials:

docker login

Then, tag your image with the registry URL:

docker tag your-image-name username/repository:tag

Finally, push the tagged image to the registry:

docker push username/repository:tag

Building container images is a crucial aspect of using Docker, as it enables you to package and deploy your applications with ease. By creating a Dockerfile with precise instructions, you can effortlessly build and distribute images across various platforms.