What is the Difference between an Image, Container and Engine?
Answer: An image is a read-only template that contains all the necessary files and dependencies to run an application. A container is an instance of an image that is running as a process on a host machine. The Docker engine is a client-server application that runs on the host machine and manages the creation, deployment, and running of containers.
What is the Difference between the Docker command COPY vs ADD?
Answer: The COPY command is used to copy files from the host machine to the container. It only supports copying local files and directories. The ADD command is similar to the COPY command but has additional features like support for URLs and the ability to extract tar archives.
What is the Difference between the Docker command CMD vs RUN?
Answer: The RUN command is used to execute commands during the build process of an image. It is used to install packages, create directories, and perform other actions that are needed to create an image. The CMD command, on the other hand, is used to specify the command that will be run when a container is started from the image.
How Will you reduce the size of the Docker image?
Answer: To reduce the size of a Docker image, you can follow these practices:
Use a smaller base image
Remove unnecessary files and dependencies
Use multi-stage builds to reduce the number of layers
Compress files in the image
Why and when to use Docker?
Answer: Docker is used to create, deploy, and run applications in a portable and efficient manner. It provides a way to package an application and its dependencies into a single container that can be run on any machine that has Docker installed. Docker is particularly useful in scenarios where you need to run applications in different environments or on different machines.
Explain the Docker components and how they interact with each other.
Answer: Docker consists of the following components:
Docker daemon: It is a server that manages the creation, deployment, and running of containers.
Docker client: It is a command-line tool that allows users to interact with the Docker daemon.
Docker registry: It is a repository for Docker images.
Docker image: It is a read-only template that contains all the necessary files and dependencies to run an application.
Docker container: It is an instance of an image that is running as a process on a host machine.
The Docker client communicates with the Docker daemon to manage images and containers. The Docker daemon pulls images from the Docker registry and creates containers from them.
Explain the terminology: Docker Compose, Docker File, Docker Image, Docker Container?
Docker Compose: It is a tool for defining and running multi-container Docker applications. It allows you to define the services, networks, and volumes for an application in a single YAML file.
Docker File: It is a script that contains instructions to build a Docker image.
Docker Image: It is a read-only template that contains all the necessary files and dependencies to run an application.
Docker Container: It is an instance of an image that is running as a process on a host machine.
Docker vs Hypervisor?
Answer: Docker and hypervisor are both used for virtualization, but they work in different ways. Hypervisors create virtual machines (VMs) that run an entire operating system, including its own kernel. Docker, on the other hand, uses containerization to run applications on the host operating system. Containers share the kernel of the host operating system, making them more lightweight and efficient than VMs. Docker is designed to run many containers on a single host, while hypervisors are designed to run multiple VMs on a single host.
What are the advantages and disadvantages of using docker?
Advantages:
Portability: Docker containers can run on any platform that supports Docker, regardless of the underlying hardware and software.
Scalability: Docker makes it easy to scale applications horizontally by adding or removing containers as needed.
Resource efficiency: Containers are lightweight and share resources, so they can run more applications on the same hardware compared to virtual machines.
Consistency: Docker ensures that the environment in which an application runs is consistent across different platforms, making it easier to deploy and maintain applications.
Disadvantages:
Complexity: Docker has a steep learning curve and requires expertise to configure and manage containers effectively.
Security: Containers can be vulnerable to security issues if they are not properly configured or secured.
Persistence: Containers are designed to be ephemeral, meaning that they are typically used for short-lived applications. For persistent storage, additional configuration is required.
What is a Docker namespace?
Answer: Docker namespaces are used to provide process isolation for containers. Each container has its own namespace for processes, networking, filesystem, and other system resources. This ensures that each container is isolated from other containers and the host system.
What is a Docker registry?
Answer: A Docker registry is a repository that stores Docker images. It can be a public or private repository and can be hosted on-premises or in the cloud. Docker images can be pushed to and pulled from a registry, making it easy to share and distribute Docker images across different platforms.
What is an entry point?
Answer: In Docker, an entry point is the first command that is executed when a container starts. It specifies the command that will run inside the container and can be used to configure the container environment.
How to implement CI/CD in Docker?
Answer: CI/CD (Continuous Integration/Continuous Deployment) can be implemented in Docker by automating the build, test, and deployment process using tools like Jenkins, Travis CI, or CircleCI. The CI/CD pipeline can be defined in a configuration file (e.g., Jenkinsfile) that specifies the steps required to build, test, and deploy the Docker image. The pipeline can be triggered automatically whenever changes are made to the source code, ensuring that the application is continuously built, tested, and deployed.
Will data on the container be lost when the docker container exits?
Answer: By default, data on the container will be lost when the container exits. However, data can be persisted by using Docker volumes, which allow data to be stored outside of the container's filesystem and shared between containers.
What is a Docker swarm?
Answer: Docker swarm is a clustering and orchestration tool for Docker containers. It allows multiple Docker hosts to work together as a cluster, enabling high availability and scalability for containerized applications. Docker swarm can be used to deploy and manage containerized applications across a cluster of hosts, making it easier to manage and scale applications.
Happy Learning!