DevOps & Cloud 路 Intern to senior
Docker is expected knowledge for DevOps engineers and increasingly for backend and full stack developers. Interviewers check that you understand what a container actually is, can write a small, secure image, and know how containers keep data and talk to each other.
5 questions
A virtual machine runs a full guest operating system on virtualised hardware, while a container shares the host鈥檚 kernel and isolates only the process, its filesystem and resources, which makes containers much lighter and faster to start.
An image is a read-only template made of layers that contains the application and its dependencies; a container is a running (or stopped) instance of an image with its own writable layer on top.
Volumes are storage managed by Docker that lives outside a container鈥檚 writable layer, so data such as database files survives when the container is removed or replaced.
Use a small, pinned base image, order instructions so dependencies are cached before source code, use multi-stage builds to leave build tools out of the final image, run as a non-root user and keep secrets out of the image.
Docker Compose defines a multi-container application (services, networks and volumes) in one YAML file so you can start, stop and rebuild the whole stack with a single command, typically for local development and testing.