| title | datePublished | cuid | slug | cover | ogImage | tags |
|---|---|---|---|---|---|---|
Day 21 Docker Important interview Questions. |
Sat Aug 19 2023 20:18:17 GMT+0000 (Coordinated Universal Time) |
clligot30000009la1wx5bhjz |
day-21-docker-important-interview-questions |
cloud, docker, devops, 2articles1week, 90daysofdevops |
Docker Image:- Docker image is just a blueprint of the docker container.
Docker Container:- Docker container is the running instance of the docker image
Docker Engine:- Docker engine is platform software to manage the image and docker container to store the data.
Copy:- the copy command used to copy the data from local directories to a specific location with the docker image.
ADD:- The ADD command has a similar purpose as COPY but offers some additional functionality. It can copy local files and directories from the host machine to the Docker image, but it also has some extra features, such as automatic URL fetching and extraction of compressed archives. The syntax of the ADD command is similar to COPY.
RUN:- Run is used to execute commands during the image build process to modify the image's filesystem.
CMD:- Cmd is used to define the default command that should be executed when a container is started from the image.
Both commands play important roles in Dockerfiles to define how images are built and how containers behave when run.
You can reduce the size of the Docker images by following the below steps:
-Use a smaller base image.
-Minimize the number of layers.
-Clean up unnecessary files and dependencies.
Docker is an open-source platform for developing, shipping and running applications in a consistent and isolated environment. It uses containerization technology to package an application and its dependencies into a single, lightweight, and portable container. Here are some key reasons why and when to use Docker:
Docker containers encapsulate an application along with its dependencies, runtime, and configuration. This ensures that the application runs consistently across different environments, from development to production. This eliminates the "it works on my machine" problem and reduces environment-related issues.
Docker images can be versioned, allowing you to roll back to previous versions of your application easily. This is useful for maintaining and reverting to known working states.
Docker is an open-source platform for developing, shipping and running applications in a consistent and isolated environment. It uses containerization technology to package an application and its dependencies into a single, lightweight, and portable container.
Docker Deamon: This is the background service responsible for building, running, and managing containers.
Docker Clients: The command-line tool or API that interacts with the Docker Daemon.
Docker Images: Images are the templates used to create Docker containers.
Docker Containers: Containers are instances created from Docker images.
Docker Registry: A repository for Docker images.
Docker Compose A tool for defining and running multi-container applications using a YAML file.
Docker Networking: Docker provides various network drivers to facilitate communication between containers and with the outside world.
Docker Volumes: Volumes provide persistent data storage for containers.
Dockerfile: A text file containing instructions to build a Docker image.
Docker-Compose:- Docker compose is reduced few steps to create a docker image and docker container with the help of docker-compose you can create multiple docker containers in a single step for docker-compose to write the yaml script. then the docker container will be created in a few sec. by reducing lots of steps
Dockerfile:- Script for building a Docker image.
Docker image:- Blueprint for creating containers.
Docker Container:- Running instance of an image.
I have used Docker for:
Development environment replication.
Microservices deployment and scaling.
Continuous integration and delivery pipelines.
Hypervisor:- hypervisor is a piece of software or firmware that creates and runs the virtual machine. A hypervisor is sometimes also called a virtual machine manager (VMM).
Docker:- Docker is an open-source centralized platform designed to create, deploy and run applications.
docker uses a container on the host o.s. to run applications. it allows applications to use the same Linux kernel as a system on the host computer, rather than creating a whole virtual O.S.
We can install docker on any O.S. but docker can run only the same O.S.
docker is written in the 'GO' language.
Advantage:-
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No pre-allocation of RAM.
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CI Efficiency Docker enables you to build a container image and use that same image across every step of the deployment process.
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it is light in weight
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It can run on physical H/w virtual H/W or on the cloud.
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you can re-use the image
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It took very less time to create a container.
image ------->container
Disadvantages:
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Docker is not a good solution for application that requires rich GUI.
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Difficult to manage a Large number of containers.
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Docker doesn't provide cross-platform compatibility means if an application is designed to run in a docker container on Windows that it can't run on Linux or vice-versa.
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docker is suitable when the development O.S. and testing O.S. are the same if the O.S. is different we should VM.
Mechanism to isolate processes, users, and resources in containers.
Storage for Docker images, on Docker Hub(public) or private registries.
Default command to execute when a container starts.
Using the entry point allows you to define the core functionality of the container and ensures that the desired process is always executed when the container starts. This helps make your Docker images more self-contained and easier to manage.
Use Docker images for consistent build and deployment environments.
Automate image creation and deployment using tools like Jenkins or GitLab CI/CD.
Data in a container is lost if not stored in a persistent volume.
Native clustering and orchestration solution for Docker, managing a group of Docker nodes as a single virtual system.
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view running containers
docker ps
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command to run the container under a specific name
docker run --name <container_name> <image_name>
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command to export a docker
ocker export <container_id> > <output_file>.tar
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command to import an already existing docker image
docker import <input_file>.tar <image_name>:
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commands to delete a container
docker rm <container-name> or <container-id>
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command to remove all stopped containers, unused networks, build caches, and dangling images?
docker prune -a
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What are the common Docker practices to reduce the size of Docker Images?
Use a Minimal Base Image: Start with a minimal base image, such as Alpine Linux, to reduce the initial image size
Multi-Stage Builds: This helps discard unnecessary build dependencies, resulting in a smaller final image.
Minimize Layers: Reduce the number of layers in your Dockerfile. Combine multiple RUN commands into a single command.
Minimize Image Layers: Avoid installing software, copying files, and running commands in separate layers if they can be combined.
Remove Unnecessary Dependencies: Avoid installing packages or dependencies that your application doesn't need.Clean Up after installation: Remove temporary files, caches, and unnecessary artifacts after each build step to minimize the size of the final image.
Use .dockerignore: Use a .dockerignore file to exclude unnecessary files and directories from being copied into the image during the build process.
Use COPY Instead of ADD: Use the COPY command instead of ADD to copy files into the image. COPY only handles local files, which is safer and more predictable.
Avoid running unnecessary services: Minimize services and processes running in the container, only including what's essential for the application to function.