Construcción de Imágenes Multi-stage

How to create efficient Docker images?

Creating efficient Docker images is essential for any developer or technology professional looking to optimize their applications and working environments. Here's how you can start creating images that are not only functional, but also lightweight and easy to maintain.

When starting to create images with Docker, the main goal is to keep the Dockerfile as simple as possible. This reduces the chances of errors and makes it easier to manage and update images.

What is a Dockerfile and how is it structured?

A Dockerfile is a text file that contains all the instructions needed to create a Docker image. For example, for a Python back-end application, the basics would be:

FROM python:3.8WORKDIR /appCOPY . /appRUN pip install -r requirements.txtCMD ["python", "app.py"]

This simple example installs the requirements and copies the files needed to run the application. However, for more complex projects, this simple structure can quickly grow in size.

What are multi-stage builds?

In larger projects, using Docker with multi-stage builds can be critical. Why? Because it allows you to build smaller, optimized images by selecting only the necessary components.

Let's look at an example with ASP.NET, where Visual Studio creates a multi-stage Dockerfile. An example of a multi-stage Dockerfile could be:

# Stage 1 - Build the applicationFROM mcr.microsoft.com/dotnet/sdk:5.0 AS buildWORKDIR /srcCOPY ["MyApp.csproj", "./"]RUN dotnet restore "MyApp.csproj"COPY . .RUN dotnet build "MyApp.csproj" -c Release -o /app/build
 # Stage 2 - Publish the applicationFROM build AS publishRUN dotnet publish "MyApp.csproj" -c Release -o /app/publish
 # Stage 3 - Build the runtime imageFROM mcr.microsoft.com/dotnet/aspnet:5.0WORKDIR /appCOPY --from=publish /app/publish .ENTRYPOINT ["dotnet", "MyApp.dll"]

How do multiple stages reduce the size of the image?

By using multiple stages, we ensure that only the necessary files are included at the end of the process. Dependencies and development files that are not necessary for the deployment of the application are removed.

First the application is compiled, only the assemblies are published and then copied to the final container. This means that the final container size is considerably smaller, which is more efficient for deploying and scaling applications in production.

Why is it important to optimize the use of Docker?

Implementing these practices allows you to not only reduce the size of images and optimize their use, but also helps improve development time. Upgrades become a simple process, and containerized infrastructure offers greater flexibility and control, which is essential in microservices and devops environments.

By following these practical tips, you can ensure that your projects are agile, efficient and prepared for any technical challenges that come your way - go ahead and continue to explore and optimize the use of Docker in your future developments!