IQ Docker / Kubernetes
Q9. What are Docker Namespaces?
Answer: The Namespaces in Docker is a technology which provides isolated workspaces called the Container. Namespaces provide a layer of isolation for the Docker containers.
Docker Container?
Containers are instances of Docker images that can be run using the Docker run command. The basic purpose of Docker is to run containers. Running of containers is managed with the Docker run command. To run a container in an interactive mode, first launch the Docker container. sudo docker run -it centos /bin/bash List containers Docker ps
What is a container image?
A container image is an unchangeable, static file that includes executable code so it can run an isolated process on the infrastructure. The image is comprised of system libraries, system tools and other platforms settings a software program needs to run on a containerization platform such as Docker or CoreOS Rkt. The image shares the OS kernel of its host machine. Containers are instances of Docker images that can be run using the Docker run command. The basic purpose of Docker is to run containers.
Docker Images?
An image is a combination of a file system and parameters. docker run hello-world The Docker command is specific and tells the Docker program on the Operating System that something needs to be done. The run command is used to mention that we want to create an instance of an image, which is then called a container. Finally, "hello-world" represents the image from which the container is made.
What is Docker Container?
Answer: A Docker Container is a form of encapsulation to the application which holds all the dependencies which share the kernel with other containers in the duration of running the isolated processes on the host operating system. A Docker container can be created by creating a Docker image. These Docker images can be run after that using Docker commands. Docker containers are the instances of the Docker images at the runtime. Docker images can be stored in any public hosts or private hosts like Docker hub. Docker Image is a set of files which can be run in an isolated process.
Q6. What is a Docker Registry?
Answer: A Docker Registry is a place where all the Docker Images will be stored and Docker Cloud and Docker Hub are the public registries where these images can be hosted upon. The Docker hub is the default storage for the Docker Images. An own registry can also be set up as per the requirement. Docker Data Center (DDC) can also be used which includes DTR (Docker Trusted Registry). Docker store will provide the feature of buying and selling the Docker images.
What is a Docker?
Answer: A Docker is defined as the platform for containerizing the applications to isolate it from each other in order to ensure high availability and more efficiency irrespective of the environments such as Development, Testing or Production. All the application related dependencies such as libraries, jar files, server related configurations, infrastructure-related elements will be packaged and formed as container called containerized application which does not need any dependency and works independently. It ensures the application to be run irrespective of the external factors. Containers in Docker have support from Docker Engine and Host Operating System to support all the operational or infrastructural related dependencies.
What are Docker Image and Docker Hub?
Answer: The Docker Image is a set of files and a combination of parameters which will allow creating the instances to run in separate containers as an isolated process. The Docker hub is a kind of repository to the images where these images can be stored and this access is public. The Docker run command can be used to create the instance called container which can be run using the Docker image. Docker hub is the largest public repository of the image containers which is being maintained by the community of developers and individual contributors.
Q8. What are Docker Objects?
Answer: The Docker Objects are Docker Images, Services, and Docker Containers. A Docker Image is a read-only template with the configuration or runtime instructions for the Docker container. The Services allow scaling the containers across the different Docker Daemons. These all together work as Swarm.
What are the components of Docker Architecture and explain?
Answer: The Docker works on client-server architecture. The Docker client establishes communication with the Docker Daemon. The Docker client and Daemon can run on the same system. A Docket client can also be connected to a remote Docker Daemon. The different types of Docker components in a Docker architecture are- 1.Docker Client: This performs Docker build pull and run operations to establish communication with the Docker Host. The Docker command uses Docker API to call the queries to be run. 2.Docker Host: This component contains Docker Daemon, Containers and its images. The images will be the kind of metadata for the applications which are containerized in the containers. The Docker Daemon establishes a connection with Registry. 3.Registry: This component will be storing the Docker images. The public registries are Docker Hub and Docker Cloud which can be s used by anyone.
What are the different functionalities and applications of using Docker?
Answer: The different functionalities and applications of using and implementing Docker are as below: It simplifies the configuration and provides ease at infrastructure level configuration. It manages the code pipeline easily which provides consistent environment and stability in the application. It enables the isolation of the application. It improves the productivity of the developer by allowing the developer to solely concentrate on business logic. It enables a lot of debugging capabilities that provides extreme useful functionalities to implement. It enables rapid deployment in the form of virtualization at the operating system level. It reduces the utilization of multiple servers in the form of containerization.
Q7. What is the lifecycle of Docker Container?
Answer: This is the most popular Docker Interview Questions asked in an interview. The life cycle of the Docker container is as below: Create a container. Run the Docker container. Pause the Container. Unpause the Container. Start the Container. Stop the Container. Restart the Container. Kill the Container. Destroy the Container.
What is containerization?
Application containerization is an OS-level virtualization method used to deploy and run distributed applications without launching an entire virtual machine (VM) for each app. Multiple isolated applications or services run on a single host and access the same OS kernel. Containers work on bare-metal systems, cloud instances and virtual machines, across Linux and select Windows and Mac OSes. -- Containerization is a lightweight alternative to full machine virtualization that involves encapsulating an application in a container with its own operating environment. This provides many of the benefits of loading an application onto a virtual machine, as the application can be run on any suitable physical machine without any worries about dependencies.
Containerization and microservices?
Application containerization works with microservices and distributed applications, as each container operates independently of others and uses minimal resources from the host. Each microservice communicates with others through application programming interfaces, with the container virtualization layer able to scale up microservices to meet rising demand for an application component and distribute the load. This setup also encourages flexibility. For example, if a developer desires a variation from the standard image, he can create a container that holds only the new library.
How application containerization works?
Application containers include the runtime components -- such as files, environment variables and libraries -- necessary to run the desired software. Application containers consume fewer resources than a comparable deployment on virtual machines because containers share resources without a full operating system to underpin each app. The complete set of information to execute in a container is the image. The container engine deploys these images on hosts.
What is a container?
Containers are packages that rely on virtual isolation to deploy and run applications that access a shared operating system (OS) kernel without the need for virtual machines (VMs). Container images include the information that executes at runtime on the OS, via a container engine. Containerized applications can be composed of several container images. For example, a 3-tier application can be composed of front-end web server, application server and database containers, which each execute independently.
How containers work?
Containers hold the components necessary to run desired software. These components include files, environment variables, dependencies and libraries. The host OS constrains the container's access to physical resources, such as CPU, storage and memory, so a single container cannot consume all of a host's physical resources.
Docker file?
Create own docker images A Docker File is a simple text file with instructions on how to build your images.
Docker Components?
Docker for Mac − It allows one to run Docker containers on the Mac OS. Docker for Linux − It allows one to run Docker containers on the Linux OS. Docker for Windows − It allows one to run Docker containers on the Windows OS. Docker Engine − It is used for building Docker images and creating Docker containers. Docker Hub − This is the registry which is used to host various Docker images. Docker Compose − This is used to define applications using multiple Docker containers.
Docker features?
Docker has the ability to reduce the size of development by providing a smaller footprint of the operating system via containers. With containers, it becomes easier for teams across different units, such as development, QA and Operations to work seamlessly across applications. You can deploy Docker containers anywhere, on any physical and virtual machines and even on the cloud. Since Docker containers are pretty lightweight, they are very easily scalable.
Q10. What are the important Docker commands?
Dockerd- To launch Docker daemon. Build- To build an image file for docker. create - To create a new container. kill-To kill a container. commit -To create a new image from container changes.
Application containerization benefits and drawbacks?
Proponents of containerization point to gains in efficiency for memory, CPU and storage compared to traditional virtualization and physical application hosting. Without the overhead required by VMs, it is possible to support many more application containers on the same infrastructure. Portability is another benefit. As long as the OS is the same across systems, an application container can run on any system and in any cloud without requiring code changes. There are no guest OS environment variables or library dependencies to manage. Draw backs - security, OS-lock in
Why do you need Kubernetes?
Real production apps span multiple containers. Those containers must be deployed across multiple server hosts. Security for containers is multilayered and can be complicated. That's where Kubernetes can help. Kubernetes gives you the orchestration and management capabilities required to deploy containers, at scale, for these workloads. Kubernetes orchestration allows you to build application services that span multiple containers, schedule those containers across a cluster, scale those containers, and manage the health of those containers over time. With Kubernetes you can take real steps towards better IT security.
Application containerization vs. virtualization and system containers?
Server virtualization abstracts the operating system and application from the underlying hardware or virtual resources. A hypervisor layer resides between memory, compute and storage and the operating system and application and services. Each application runs on its own version of an OS. This allows different applications on the same host to use different OS versions, but it also consumes more resources than containers, and it requires more OS licenses than a containerized setup. Containers can run inside of virtual machines, which means a host machine could have multiple OSes supporting multiple containers all sharing the same physical resources. Application containers create a safe space for app code to consume host resources without acknowledging or depending upon the existence of other applications using the same OS. System containers perform a role similar to virtual machines, but without hardware virtualization. System containers, also called infrastructure containers, include the host operating system, application libraries and execution code. System containers can host application containers.
What can you do with Kubernetes?
The primary advantage of using Kubernetes in your environment, especially if you are optimizing app dev for the cloud, is that it gives you the platform to schedule and run containers on clusters of physical or virtual machines. More broadly, it helps you fully implement and rely on a container-based infrastructure in production environments. And because Kubernetes is all about automation of operational tasks, you can do many of the same things that other application platforms or management systems let you do, but for your containers. With Kubernetes you can: Orchestrate containers across multiple hosts. Make better use of hardware to maximize resources needed to run your enterprise apps. Control and automate application deployments and updates. Mount and add storage to run stateful apps. Scale containerized applications and their resources on the fly. Declaratively manage services, which guarantees the deployed applications are always running how you deployed them. Health-check and self-heal your apps with autoplacement, autorestart, autoreplication, and autoscaling. Kubernetes, however, relies on other projects to fully provide these orchestrated services. With the addition of other open source projects, you can fully realize the power of Kubernetes. These necessary pieces include (among others): Registry, through projects like Atomic Registry or Docker Registry. Networking, through projects like OpenvSwitch and intelligent edge routing. Telemetry, through projects such as heapster, kibana, hawkular, and elastic. Security, through projects like LDAP, SELinux, RBAC, and OAUTH with multi-tenancy layers. Automation, with the addition of Ansible playbooks for installation and cluster life-cycle management. Services, through a rich catalog of precreated content of popular app patterns.
Docker Architecture?
Traditional virtualization -(multiple)App/GuestOS -Hypervisor -Host OS -Server The server is the physical server that is used to host multiple virtual machines. The Host OS is the base machine such as Linux or Windows. The Hypervisor is either VMWare or Windows Hyper V that is used to host virtual machines. You would then install multiple operating systems as virtual machines on top of the existing hypervisor as Guest OS. You would then host your applications on top of each Guest OS. Docker -App(Multiple) -Docker Engin -Host OS -Server The server is the physical server that is used to host multiple virtual machines. So this layer remains the same. The Host OS is the base machine such as Linux or Windows. So this layer remains the same. Now comes the new generation which is the Docker engine. This is used to run the operating system which earlier used to be virtual machines as Docker containers. All of the Apps now run as Docker containers. The clear advantage in this architecture is that you don't need to have extra hardware for Guest OS. Everything works as Docker containers.
What is Kubernetes?
is an open source platform that automates Linux container operations. It eliminates many of the manual processes involved in deploying and scaling containerized applications. In other words, you can cluster together groups of hosts running Linux containers, and Kubernetes helps you easily and efficiently manage those clusters. These clusters can span hosts across public, private, or hybrid clouds. For this reason, Kubernetes is an ideal platform for hosting cloud-native applications that require rapid scaling, like real-time data streaming through Apache Kafka.
