Docker Questions

What is a registry?

A Docker registry is an open-source server-side service used for hosting and distributing Docker images In a registry, a user can distinguish between Docker images with their tag names Docker also has its own default registry called Docker Hub

What is a docker image?

- Docker images are templates of Docker containers -An image is built using a Dockerfile -It is stored in a Docker repository or a Docker hub -The image layer is a read-only filesystem

What is a docker container?

-Containers are runtime instances of a Docker image -Containers are created using Docker images -They are stored in the Docker daemon -Every container layer is a read-write filesystem

What is a Dockerfile used for?

A Dockerfile is used for creating Docker images using the build command. With a Docker image, any user can run the code to create Docker containers. Once a Docker image is built, it's uploaded in a Docker registry. From the Docker registry, users can get the Docker image and build new containers whenever they want.

How is a bare repository different from the standard way of initializing a Git repository?

Using the standard method: git init You create a working directory with git init A .git subfolder is created with all the git-related revision history Using the bare way git init --bare -It does not contain any working or checked out a copy of source files -Bare repositories store git revision history in the root folder of your repository, instead of the .git subfolder

What do you know about DevOps?

Your answer must be simple and straightforward. Begin by explaining the growing importance of DevOps in the IT industry. Discuss how such an approach aims to synergize the efforts of the development and operations teams to accelerate the delivery of software products, with a minimal failure rate. Include how DevOps is a value-added practice, where development and operations engineers join hands throughout the product or service lifecycle, right from the design stage to the point of deployment.

Explain the architecture of Docker

-Docker uses a client-server architecture. -Docker Client is a service that runs a command. The command is translated using the REST API and is sent to the Docker Daemon (server). -Docker Daemon accepts the request and interacts with the operating system to build Docker images and run Docker containers. -A Docker image is a template of instructions, which is used to create containers. -Docker container is an executable package of an application and its dependencies together. -Docker registry is a service to host and distribute Docker images among users.

What is the role of configuration management in DevOps?

-Enables management of and changes to multiple systems. -Standardizes resource configurations, which in turn, manage IT infrastructure. -It helps with the administration and management of multiple servers and maintains the integrity of the entire infrastructure.

What is continuous delivery?

-Ensures code can be safely deployed on to production -Ensures business applications and services function as expected -Delivers every change to a production-like environment through rigorous automated testing

What is continuous deployment?

-Every change that passes the automated tests is deployed to production automatically -Makes software development and the release process faster and more robust -There is no explicit approval from a developer and requires a developed culture of monitoring

Why Has DevOps Gained Prominence over the Last Few Years?

-Investing in DevOps to automate and accelerate application deployment and how this has helped them grow their business. -Using Facebook as an example, you would point to Facebook's continuous deployment and code ownership models and how these have helped it scale up but ensure the quality of experience at the same time. -Hundreds of lines of code are implemented without affecting quality, stability, and security. Fully automated processes and systems to handle large amount of users to your applications. Mention the user base of these two organizations: Facebook has 2 billion users while Netflix streams online content to more than 100 million users worldwide. These are great examples of how DevOps can help organizations to ensure higher success rates for releases, reduce the lead time between bug fixes, streamline and continuous delivery through automation, and an overall reduction in manpower costs.

Instead of YAML, what can you use as an alternate file for building Docker compose?

-To build a Docker compose, a user can use a JSON file instead of YAML. -In case a user wants to use a JSON file, he/she should specify the filename as given: Docker-compose -f Docker-compose.json up

Explain the term "Infrastructure as Code" (IaC) as it relates to configuration management.

-Writing code to manage configuration, deployment, and automatic provisioning. -Managing data centers with machine-readable definition files, rather than physical hardware configuration. -Ensuring all your servers and other infrastructure components are provisioned consistently and effortlessly. -Administering cloud computing environments, also known as infrastructure as a service (IaaS).

What is Git stash?

A developer working with a current branch wants to switch to another branch to work on something else, but the developer doesn't want to commit changes to your unfinished work. The solution to this issue is Git stash. Git stash takes your modified tracked files and saves them on a stack of unfinished changes that you can reapply at any time.

What is the role of AWS in DevOps?

AWS has the following role in DevOps: Flexible services - Provides ready-to-use, flexible services without the need to install or set up the software. Built for scale - You can manage a single instance or scale to thousands using AWS services. Automation - AWS lets you automate tasks and processes, giving you more time to innovate Secure - Using AWS Identity and Access Management (IAM), you can set user permissions and policies. Large partner ecosystem - AWS supports a large ecosystem of partners that integrate with and extend AWS services.

Explain the difference between a centralized and distributed version control system (VCS).

Centralized Version Control System -All file versions are stored on a central server -No developer has a copy of all files on a local system -If the central server crashes, all data from the project will be lost Distributed Control System -Every developer has a copy of all versions of the code on their systems -Enables team members to work offline and does not rely on a single location for backups -There is no threat, even if the server crashes

How does continuous monitoring help you maintain the entire architecture of the system?

Continuous monitoring in DevOps is a process of detecting, identifying, and reporting any faults or threats in the entire infrastructure of the system. -Ensures that all services, applications, and resources are running on the servers properly. -Monitors the status of servers and determines if applications are working correctly or not. -Enables continuous audit, transaction inspection, and controlled monitoring.

What are the commands used to create a Docker swarm?

Create a swarm where you want to run your manager node. Docker swarm init --advertise-addr <MANAGER-IP> Once you've created a swarm on your manager node, you can add worker nodes to your swarm. When a node is initialized as a manager, it immediately creates a token. In order to create a worker node, the following command (token) should be executed on the host machine of a worker node. docker swarm join \ --token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \ 192.168.99.100:2377

How is DevOps different from agile methodology?

DevOps is a culture that allows the development and the operations team to work together. This results in continuous development, testing, integration, deployment, and monitoring of the software throughout the lifecycle. -Agile is a software development methodology that focuses on iterative, incremental, small, and rapid releases of software, along with customer feedback. It addresses gaps and conflicts between the customer and developers. -DevOps addresses gaps and conflicts between the Developers and IT Operations

What is the purpose of the expose command in Docker?

Expose Expose is an instruction used in Dockerfile. It is used to expose ports within a Docker network. It is a documenting instruction used at the time of building an image and running a container. Expose is the command used in Docker. Example: Expose 8080

How do you push a file from your local system to the GitHub repository using Git?

First, connect the local repository to your remote repository: git remote add origin [copied web address] // Ex: git remote add origin https://github.com/Simplilearn-github/test.git Second, push your file to the remote repository: git push origin master

What is git fetch?

Git fetch downloads new data from a remote repository Does not integrate any new data into your working files Users can run a Git fetch at any time to update the remote-tracking branches Command: git fetch origin git fetch --all

What is git pull?

Git pull updates the current HEAD branch with the latest changes from the remote server Downloads new data and integrate it with the current working files Tries to merge remote changes with your local ones Command: git pull origin master

How do you run multiple containers using a single service?

It is possible to run multiple containers as a single service with Docker Compose. Here, each container runs in isolation but can interact with each other. All Docker Compose files are YAML files.

How do we share Docker containers with different nodes?

It is possible to share Docker containers on different nodes with Docker Swarm. Docker Swarm is a tool that allows IT administrators and developers to create and manage a cluster of swarm nodes within the Docker platform. A swarm consists of two types of nodes: a manager node and a worker node.

What are the advantages of Docker over virtual machines?

Memory Space: Dockers containers occupy less space Boot-up time: Short boot-up time Performance: Containers have a better performance, as they are hosted in a single Docker engine Scaling: Easy to scale up Efficiency: High efficiency Portability: Easily portable across different platforms Space Allocation: Data volumes are shared and used again across multiple containers

Why are virtual machines bad?

Memory Space: Virtual machines occupies a lot of memory space Boot-up time: Long boot-up time Performance: Running multiple virtual machines leads to unstable performance Scaling: Difficult to scale up Efficiency: Low efficiency Portability: Compatibility issues while porting across different platforms Space Allocation: Data volumes cannot be shared

What is the purpose of the publish command in Docker?

Publish is used in a Docker run command. It can be used outside a Docker environment. It is used to map a host port to a running container port. --publish or -p is the command used in Docker. Example: docker run -d -p 0.0.0.80:80

How is IaC implemented using AWS?

Start by talking about the age-old mechanisms of writing commands onto script files and testing them in a separate environment before deployment and how this approach is being replaced by IaC. Similar to the codes written for other services, with the help of AWS, IaC allows developers to write, test, and maintain infrastructure entities in a descriptive manner, using formats such as JSON or YAML. This enables easier development and faster deployment of infrastructure changes.

What is the difference between Git Merge and Git Rebase?

Suppose you are working on a new feature in a dedicated branch, and another team member updates the master branch with new commits. You can use these two functions: Git Merge -To incorporate the new commits into your feature branch, use Git merge. -Creates an extra merge commit every time you need to incorporate changes -But, it pollutes your feature branch history Git Rebase -As an alternative to merging, you can rebase the feature branch on to master. -Incorporates all the new commits in the master branch -It creates new commits for every commit in the original branch and rewrites project hist

Explain the concept of branch in Git.

Suppose you are working on an application, and you want to add a new feature to the app. You can create a new branch and build the new feature on that branch. By default, you always work on the master branch. The circles on the branch represent various commits made on the branch. After you are done with all the changes, you can merge it with the master branch.

How do you create a Docker container?

Task: Create a MySQL Docker container A user can either build a Docker image or pull an existing Docker image (like MySQL) from Docker Hub. Now, Docker creates a new container MySQL from the existing Docker image. Simultaneously, the container layer of the read-write filesystem is also created on top of the image layer. -Command to create a Docker container: Docker run -t -i MySQL -Command to list down the running containers: Docker ps

How do you find a list of files that have been changed in a particular commit?

The command to get a list of files that have been changed in a particular commit is: git diff-tree -r {commit hash} Example: git diff-tree -r 87e673f21b -r flag instructs the command to list individual files -commit hash will list all the files that were changed or added in that commit

Mention some of the core benefits of DevOps.

The core benefits of DevOps are as follows: Technical benefits -Continuous software delivery -Less complex problems to manage -Early detection and faster correction of defects Business benefits -Faster delivery of features -Stable operating environments -Improved communication and collaboration between the teams

What are the cloud platforms that support Docker?

The following are the cloud platforms that Docker runs on: -Amazon Web Services -Microsoft Azure -Google Cloud Platform -Rackspace

How will you approach a project that needs to implement DevOps?

The following standard approaches can be used to implement DevOps in a specific project: Stage 1 An assessment of the existing process and implementation for about two to three weeks to identify areas of improvement so that the team can create a road map for the implementation. Stage 2 Create a proof of concept (PoC). Once it is accepted and approved, the team can start on the actual implementation and roll-out of the project plan. Stage 3 The project is now ready for implementing DevOps by using version control/integration/testing/deployment/delivery and monitoring followed step by step. By following the proper steps for version control, integration, testing, deployment, delivery, and monitoring, the project is now ready for DevOps implementation.

Which are some of the most popular DevOps tools?

The most popular DevOps tools include: Selenium Puppet Chef Git Jenkins Ansible Docker

What is a repository?

The repository is a collection of multiple versions of Docker images It is stored in a Docker registry It has two types: public and private repositories

Name three important DevOps KPIs.

The three important KPIs are as follows: Meantime to failure recovery - This is the average time taken to recover from a failure. Deployment frequency - The frequency in which the deployment occurs. Percentage of failed deployments - The number of times the deployment fails.

What are the different phases in DevOps?

The various phases of the DevOps lifecycle are as follows: Plan - Initially, there should be a plan for the type of application that needs to be developed. Getting a rough picture of the development process is always a good idea. Code - The application is coded as per the end-user requirements. Build - Build the application by integrating various codes formed in the previous steps. Test - This is the most crucial step of the application development. Test the application and rebuild, if necessary. Integrate - Multiple codes from different programmers are integrated into one . Deploy - Code is deployed into a cloud environment for further usage. It is ensured that any new changes do not affect the functioning of a high traffic website. Operate - Operations are performed on the code if required. Monitor - Application performance is monitored. Changes are made to meet the end-user requirements.

Which of the following CLI commands can be used to rename files?

git mv