juniorDocker
What is a Dockerfile?
Updated Apr 28, 2026
Short answer
A text document containing all the commands a user could call on the command line to assemble an image.
Deep explanation
Docker leverages Linux namespaces and cgroups to provide isolation. Unlike VMs, there is no hypervisor layer overhead, allowing for near-native performance and rapid startup times.
Real-world example
A developer wants to ensure their app runs exactly the same on their laptop as it does on a colleague's machine.
Common mistakes
- Confusing 'EXPOSE' with port publishing ('-p').
Follow-up questions
- What is a 'layer' in Docker?