Q1. What is the difference between a Docker image and a container?
An image is a read-only template; a container is a running instance of that image. - Image: built from a Dockerfile, composed of immutable layers, and stored in a registr...
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Q2. What is the difference between a container and a virtual machine?
A VM virtualises hardware: each VM runs a full guest OS on a hypervisor, so it is heavy (GBs) and slow to boot (minutes) but strongly isolated. A container virtualises th...
Q3. Explain Docker layers and how caching works.
A Docker image is a stack of read-only layers. Each Dockerfile instruction creates a layer, and layers are shared between images and cached. Build cache: - Docker checks ...
Q4. What is the difference between Docker volumes and bind mounts?
Both persist data outside the container's writable layer, but they are managed differently. - Volumes are stored in a Docker-managed location under /var/lib/docker/volume...
Q5. Explain Docker networking modes.
Docker creates network namespaces and connects containers using drivers. - bridge (default): containers get private IPs on a virtual bridge. Same-network containers resol...
Q6. What is a multi-stage build and why use it?
A multi-stage build uses several FROM stages in one Dockerfile. You can compile in an early stage and copy only the artefacts into a minimal final stage. ```dockerfile FR...
Q7. How do you reduce Docker image size?
Attack the layers, base image, and build context. - Use a minimal base: alpine, distroless, or scratch for static binaries. - Use multi-stage builds: compile in one stage...
Q8. What is the difference between CMD and ENTRYPOINT?
Both define what runs when a container starts, but they behave differently. - ENTRYPOINT sets the executable. It is hard to override and defines the container's purpose. ...
Q9. How do you troubleshoot a container that exits immediately?
A container stops when its main process exits, so first find out why the process ended. 1. Inspect the exit code and state. ```bash docker ps -a docker inspect --format '...