What is the Difference between an Image, Container and Engine?
An image is a self-contained package containing all application dependencies. A container is an isolated instance of an image that runs on any system consistently. An engine, like Docker, is a platform that manages containers, simplifying the deployment and management of applications.
What is the Difference between the Docker command COPY vs ADD?
The
COPYcommand in Docker is used to copy files and directories from the host machine to the container. On the other hand, theADDcommand not only copies files but also supports downloading files from URLs and extracting compressed files. In general, it's recommended to useCOPYfor simple file copying tasks, andADDwhen additional functionality like downloading and extraction is needed.What is the Difference between the Docker command CMD vs RUN?
The
RUNcommand in Docker is used to execute commands during the image build process, such as installing dependencies. TheCMDcommand, however, is used to specify the default command that will run when a container is started from the image. In short,RUNis for build-time actions, andCMDis for runtime command definition.How Will you reduce the size of the Docker image?
To reduce the size of a Docker image, I would:
Use a smaller base image, like Alpine Linux, instead of a full-fledged OS.
Optimize Dockerfile instructions by combining commands and cleaning up unnecessary files.
Use .dockerignore to exclude unnecessary files and directories from being copied into the image. This helps achieve a more compact and efficient image size.
Why and when to use Docker?
Docker is used to simplify application deployment by creating lightweight, isolated containers that encapsulate the application and its dependencies. It allows for consistency across different environments and enables rapid development, testing, and deployment. Docker is ideal for scenarios where portability, scalability, and easy management of applications are essential, particularly in microservices architectures and cloud-based deployment
Explain the Docker components and how they interact with each other.
Docker's components include:
Docker Engine: Manages containers, running on the host machine.
Docker Images: Lightweight, executable packages containing application code and dependencies.
Docker Containers: Instances of images running in isolated environments. These components interact as follows: Docker Engine uses images to create containers, ensuring applications run consistently across different systems, facilitating seamless development, and enabling easy scaling and management of applications.
Explain the terminology: Docker Compose, Docker File, Docker Image, Docker Container?
Docker Compose : A tool used for defining and managing multi-container Docker applications. It uses a YAML file to specify the services, networks, and volumes required for the application setup.
Dockerfile: A script that contains instructions to build a Docker image. It defines the application's environment and dependencies, which can be used to create consistent and reproducible images.
Docker Image: A lightweight, standalone, and executable package that includes the application code, runtime, libraries, dependencies, and configurations required to run the application in an isolated environment.
Docker Container: An instance of a Docker image running as a separate and isolated process. Containers are isolated from each other and the host system, providing consistency and portability for applications.
In what real scenarios have you used Docker?
Docker is commonly used in real-world scenarios such as microservices-based application deployment, facilitating CI/CD pipelines, and ensuring consistent development and testing environments for teams working on various platforms.
Docker vs Hypervisor?
Docker is a containerization platform that virtualizes applications, isolating them in lightweight containers, sharing the host OS kernel for efficiency. Hypervisors, like VMware or Hyper-V, are virtualization technologies that create multiple virtual machines, each with its own OS, on a single physical server. Docker offers faster startup times, lower resource overhead, and greater portability, while hypervisors provide stronger isolation between VMs and support different operating systems. The choice depends on the use case: Docker for application-level virtualization and hypervisors for full OS-level virtualization.
What are the advantages and disadvantages of using docker?
Advantages:
Portability: Docker provides consistent environments, making applications easily portable across different systems.
Scalability: It enables efficient scaling of applications using container orchestration platforms like Kubernetes.
Resource Efficiency: Docker's lightweight containers use fewer resources compared to traditional virtual machines.
Disadvantages:
Complexity: Docker introduces additional complexity, requiring knowledge of containerization concepts and tools.
Security Risks: Misconfigurations or vulnerabilities in containers can lead to security issues.
Persistence: Managing persistent data in Docker containers can be challenging, necessitating external solutions like Docker volumes.
What is a Docker namespace?
A Docker namespace is a feature that provides isolation and separation of resources between containers and the host system. It allows each container to have its unique view of system resources like processes, network interfaces, user IDs, etc. This isolation ensures that processes within one container cannot access or interfere with processes in other containers, enhancing security and stability.
What is a Docker registry?
Docker registry is like a storage center for Docker images. It's a place where developers can upload and share their container images, making it easy for others to access and use them for their applications. It's like a library of ready-to-use software packages for running applications in containers.
What is an entry point?
An entry point in Docker is like the main door of a house. It's the first thing that runs when you start a container. It's like telling Docker what program or script to run inside the container as soon as it starts up.
How to implement CI/CD in Docker?
To implement CI/CD in Docker, follow these simple steps:
Use CI/CD tools like Jenkins or GitLab CI/CD to build and test your application using Docker.
Store the built Docker images in a registry like Docker Hub.
Deploy the Docker images to your production environment with tools like Kubernetes or Docker Swarm for automatic updates and smooth operations.
Will data on the container be lost when the docker container exits?
Yes, data inside a Docker container will be lost when it exits. But you can save important data by using Docker volumes or bind mounts to keep it safe outside the container, even if the container is removed or stopped.
What is a Docker swarm?
Docker Swarm is like a team of worker bees working together. It's a built-in feature of Docker that lets you create a group of computers, called nodes, which work as a team. This way, you can run and manage lots of containers across these nodes easily, making your applications more reliable and scalable.
What are the docker commands for the following:
view running containers
command to run the container under a specific name
command to export a docker
command to import an already existing docker image
commands to delete a container
command to remove all stopped containers, unused networks, build caches, and dangling images?
view running containers:
Copy codedocker ps
Command to run the container under a specific name:
docker run --name <container_name> <image_name>
Command to export a Docker container:
docker export <container_id> > <exported_file.tar>
Command to import an already existing Docker image:
docker import <exported_file.tar>
Commands to delete a container:
docker stop <container_id>
docker rm <container_id>
Command to remove all stopped containers, unused networks, build caches, and dangling images:
docker system prune
What are the common docker practices to reduce the size of Docker Image?
To reduce the size of Docker images, common practices include:
Using smaller base images like Alpine Linux instead of full OS distributions.
Optimizing Dockerfiles by minimizing layers and cleaning up unnecessary files.
Using .dockerignore to exclude unnecessary files from being copied into the image, resulting in a more compact and efficient image size.
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