Q: What is the Difference between an Image, Container, and Engine?
A:
Image: An image is a template containing everything needed to run an application, including code, runtime, libraries, and dependencies.
Container: A container is an instance of an image running as a process on the host machine, isolated from other containers and the host system.
Engine: The Docker Engine is the core component responsible for creating and managing Docker containers. It includes the Docker daemon, API, and CLI.
Q: What is the Difference between the Docker command COPY vs ADD?
A:
COPY: Copies files or directories from the host machine to the container's filesystem. Recommended for copying local files into the container.
ADD: Similar to COPY but with additional features like URL support and automatic tar extraction. Use cautiously to avoid unexpected behavior.
Q: What is the Difference between the Docker command CMD vs RUN?
A:
CMD: Defines the default command to run when the container starts. Often used to specify the main application process.
RUN: Executes commands during the image build process to install dependencies, configure the environment, or perform other setup tasks.
Q: How Will you reduce the size of the Docker image?
A:
Use multi-stage builds.
Choose lightweight base images like Alpine Linux.
Minimize the number of layers.
Remove unnecessary files and dependencies.
Use .dockerignore file to exclude unnecessary files and directories.
Q: Why and when to use Docker?
A:
Docker simplifies application deployment by packaging applications and their dependencies into containers.
Provides consistency across different environments, making it easier to develop, test, and deploy applications.
Commonly used in microservices architectures, CI/CD pipelines, and cloud-native applications.
Q: Explain the Docker components and how they interact with each other.
A:
Docker Compose: Defines and runs multi-container Docker applications using a YAML file.
Dockerfile: Contains instructions for building a Docker image.
Docker Image: Read-only template used to create Docker containers.
Docker Container: Runnable instance of a Docker image.
Q: In what real scenarios have you used Docker?
A:
Deploying microservices-based applications.
Creating development environments with consistent dependencies.
Scaling applications horizontally with Docker Swarm or Kubernetes.
Building CI/CD pipelines for automated testing and deployment.
Q: Docker vs Hypervisor?
A:
Docker containers share the host OS kernel, resulting in lower overhead compared to hypervisors.
Hypervisors create virtual machines with their own OS, leading to higher resource consumption.
Q: What are the advantages and disadvantages of using Docker?
A:
Advantages: Portability, scalability, isolation, efficiency, and easy management.
Disadvantages: Security concerns, learning curve, potential performance overhead.
Q: What is a Docker namespace?
A:
- Docker uses namespaces to provide isolation for containers, allowing each container to have its own view of system resources like processes, network interfaces, and filesystems.
Q: What is a Docker registry?
A:
- A Docker registry is a repository for Docker images. Docker Hub is the default public registry, but organizations can also set up private registries to store and share custom images.
Q: What is an entry point?
A:
- The ENTRYPOINT instruction in a Dockerfile defines the command that will be executed when the container starts. It is similar to CMD but cannot be overridden at runtime.
Q: How to implement CI/CD in Docker?
A:
Use Docker to package applications and dependencies into containers.
Integrate Docker with CI/CD tools like Jenkins, GitLab CI, or Travis CI.
Automate the build, test, and deployment processes using Docker images and containers.
Q: Will data on the container be lost when the docker container exits?
A:
- Yes, data stored within a container's writable layer is lost when the container exits unless it is explicitly persisted using volumes or bind mounts.
Q: What is a Docker swarm?
A:
- Docker Swarm is a native clustering tool for Docker containers that allows you to create and manage a cluster of Docker hosts.
Q: What are the docker commands for the following:
View running containers:
docker psCommand to run the container under a specific name:
docker run --name <container_name>Command to export a docker:
docker export <container_id>Command to import an already existing docker image:
docker import <file_path>Commands to delete a container:
docker rm <container_id>Command to remove all stopped containers, unused networks, build caches, and dangling images:
docker system prune
Q: What are the common docker practices to reduce the size of Docker Image?
A:
Use multi-stage builds.
Minimize layers and combine commands.
Choose smaller base images.
Remove unnecessary files and dependencies.
Compress files and use efficient build techniques.
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