Why Is Docker’s Container Approach so Important?
Posted on March 10, 2017
Updated
Docker packages an application and its userspace dependencies into an image that can be distributed and run with a compatible container runtime. This improves consistency between development and delivery, while the host, architecture, network and storage still affect behavior.
Repeatable packaging
Build an image in CI, test it and promote the same digest through environments. Tags can change; a digest identifies content. Configuration and runtime secrets remain separate from the image. Rebuild with updated dependencies rather than assuming an older artifact remains secure.
Process isolation and resource control
Containers usually share the host kernel. Namespaces and resource controls separate processes and bound resource use, but they do not provide every isolation property of a virtual machine. Privileged containers and host mounts can weaken that boundary.
A practical delivery workflow
Container startup can be quick because it does not ordinarily boot a guest operating system per container. Image download, initialization and application readiness still take time. Docker Desktop can also use a Linux virtual machine, with its own resource requirements.
What should you check first?
Match the operating system and CPU architecture, run with the minimum permissions, define health checks and test persistent data handling. Compare actual build, rollout and recovery times before claiming a productivity or cost improvement.
Continue with building better container images and when container orchestration is useful.