What does Docker do in DevOps?

18 Tem 00:02

Docker is a containerization tool that standardizes application deployment and management in DevOps processes. Instead of abstracting lower layers at the operating system level like Virtual Machines (VMs), Docker packages only the environment necessary for the application and its dependencies to run inside a container. This way, what you say "works on my machine" will also work the same way in production—until you can simply say goodbye to the "it does not work on my machine" problem. Compared to VMs, Docker is lighter and starts in seconds, whereas VMs typically take several minutes. In CI/CD pipelines, Docker often sits at the center of the "build, push, deploy" triangle. For example, when designing a pipeline in GitLab CI or GitHub Actions, an image is created from the Dockerfile (`docker build`), pushed to a registry (`docker push`), and then executed on the production server (`docker run` or via Kubernetes). Common challenges when transitioning from local to production include unnecessarily large image sizes (bloat), misconfigured network policies for containers, or environment variables not being set differently in the production environment compared to local. Another frequent issue is properly injecting secrets (e.g., database passwords). To solve this, `.env` files or Kubernetes Secrets are commonly used.