Frequently Asked OpenShift Interview Questions And Answer:
Openshift Interview Question And Answers are as follows:
- What are the features of OpenShift?
Answer: You can find this entry as one of the most frequently asked OpenShift interview questions. The features of OpenShift include a rich command-line toolset, support for multiple databases and language, and an extensible cartridge system. The other features of OpenShift include the following.
- Multi-Environment support.
- One-click deployment.
- Responsive web console.
- Remote application debugging.
- Standardized workflow for developers.
- Rest API support.
- Support for remote SSH login to the application.
- In-built database services.
- Automatic application scaling.
- The facility of support for release management and continuous integration.
- IDE integration.
- What are deployment strategies?
Answer: Deployment strategies are an important part of top OpenShift interview questions. Deployment strategies are instruments for modifying or upgrading an application. With the help of deployment strategies, modifications do not require any form of downtime. The most common deployment strategy is the blue-green deployment strategy.
In this strategy, users keep using the stable version denoted by green while changes are made in the new version denoted by blue. After testing and evaluating the new version in blue color, users can switch to the blue version. If any problem arises, then users could continue with the green version.
- What are rolling deployments?
Answer: Candidates can find this question as a follow-up to the previous mention in this list of OpenShift interview questions. Rolling deployments involve the slow replacement of instances of the old version of an application by instances of a new version of the application. Rolling deployment depends on the readiness check for new pods before scaling down capacities of old components. In the case of significant issues, rolling deployment could be stalled.
- What is the Downward API in OpenShift?
Answer: Candidates could find this entry among frequently asked OpenShift interview questions. Downward API is a mechanism for pods to retrieve metadata without the need to call into Kubernetes API. Downward API is ideal for retrieving metadata and configuration of running pods.
The metadata which Downward API can retrieve include labels, annotations, pod name, namespace, and IP address. Downward API can also retrieve information about Pod CPU or memory requests and limits. Downward API may mount certain information on the pod as an environment variable. On the other hand, certain information could also be accessed as files within a volume.
- Define the OpenShift CLI.
Answer: Candidates should note the importance of CLI to form an OpenShift interview question. OpenShift CLI is a tool for the management of OpenShift applications from the command line. The OpenShift CLI provides abilities for the management of the end-to-end application lifecycle. It has the features for basic and advanced configuration for applications. Also, it includes functionalities for management, deployment, and adding applications.
- What are the feature toggles?
Answer: Feature toggles are also frequent entries among OpenShift interview questions. These are techniques that help in including old and new versions of a feature in the same code base. However, the versions are surrounded by logic for execution or based on factors such as database switch or property value. Feature toggles help in separating the deployment from usage, single group, and legacy systems, and multiple server groups.
- What the systems on the OpenShift environment running on AWS?
Answer: The OpenShift environment running on Amazon Web Services includes one master node and one infrastructure node. It also includes an NFS server and 24 application nodes.
- What can you run on OpenShift?
Answer: This entry is one of the practical and best OpenShift interview questions on this list. OpenShift is ideal for running existing Docker images and defining builds for producing new Docker images using Dockerfile.
- What type of security controls can you find on OpenShift?
Answer: OpenShift interview questions would also revolve around security concerns. The security policy of OpenShift follows certain precedents. Containers could not access host resources or run privileged. Containers have to run as non-root unique users separate from other users. Containers get CPU and memory limits according to definitions by the system administrator. Most important of all, regular users and admins could not change security quotas.
- Outline the benefits of OpenShift Origin.
Answer: The benefits of OpenShift Origin may come up among the best OpenShift interview questions. The benefits include running PaaS locally on a system and behind a firewall. OpenShift Origin also helps in improving developer competences with PaaS and the expansion of skills.
- Do you know about OpenShift cartridges?
Answer: OpenShift cartridges have also popped up as an important OpenShift interview question. OpenShift cartridges are central points for developing applications. Every cartridge has specific libraries, build mechanisms, source code, routing logic, and connection logic alongside pre-configured environment. All these factors help in running your application.
- What is the difference between gear and container?
Answer: You can find the latest OpenShift interview questions focused on difference-based evaluations. The terms ‘container’ and ‘gear’ are interchangeable. Containers have a precise mapping involving one-to-one relations among images. However, in the case of gears, many cartridges can become part of a single gear. In the case of containers, pods fulfill the collocation concept.
- What is the Source-to-Image (S2I) strategy?
Answer: This strategy involves the creation of source code images through downloading and compilation of the same container. The images are created from the same code, and with a custom strategy, rpm and jar get developed.
- How OpenShift uses Docker and Kubernetes?
Answer: Kubernetes and Docker could work OpenShift in the form of a control system. You can find this question among the latest OpenShift interview questions commonly. The control system helps in enabling many deployment pipelines that are ideal for later use in auto-scaling, testing, and other processes.
- What are the build strategies in OpenShift?
Answer: The common build strategies in OpenShift are Docker strategy, custom strategy, Source to Image strategy, and pipeline strategy.
- Why do we need DevOps tools?
Answer: The applications of DevOps tools are ideal for improving flexibility in software delivery. In addition to this, DevOps tools also help in improving deployment frequency and reducing failure rates. Furthermore, DevOps tools also help in faster recovery and better time management between repairs.
- What is the difference between OpenShift and OpenStack?
Answer: Candidates can find this question among crucial OpenShift interview questions. The primary difference is that OpenStack provides Infrastructure as a Service (IaaS). Furthermore, OpenStack is different from OpenShift by providing object storage and block storage to a bootable virtual machine.
- What are Build configurations?
Answer: Build configuration resources help in configuration and control of builds. Build configuration includes details about a specific build strategy and the source of developer-supplied artifacts like output image.
- Name some identity providers in OAUTH.
Answer: The identity providers in OAUTH are HTTPassword, LDAP, Allow All, Deny All, and Authentication.
- Do you know about OpenShift Online?
Answer: OpenShift online is the public service of Red Hat for cloud application development and hosting.
- Which projects can claim a Persistent Volume (PV) object?
Answer: Candidates could also find some tough questions like this in OpenShift interviews. The answer suggests indications towards default projects, OpenShift projects, any project, and OpenShift-infra projects.
- Name the network plugin for providing connectivity for pods across an entire cluster.
Answer: The network plugin that provides connectivity for pods across the entire cluster without any limitations is ‘ovs-subnet.’
- What are the unique components you can find in OpenShift as compared to Kubernetes?
Answer: The components unique to OpenShift in comparison to Kubernetes are the Internal registry and Router as an ingress traffic control.
- What is Volume Security?
Answer: Volume Security is ideal for the security of PV and PVC projects in OpenShift. Controlling access to volumes in OpenShift involves four main sections. The sections are Supplemental groups, fsGroup, seLinuxOptions, and runAsUser.
- What do you know about the OpenShift pipeline?
Answer: OpenShift pipeline is a tool for obtaining control over developing, deployment, and promotion of applications on OpenShift. OpenShift pipeline depends considerably on the Jenkins Pipeline Build Strategy, OpenShift Domain Specific Language (DSL), and Jenkins files.
- What is OpenShift?
OpenShift is a cloud development Platform as a Service.It is an open source development platform by which developer develops and deploys application on cloud.
- What is OpenShift online?
It is public PaaS of OpenShift community using which one can build and deploy its application on public cloud. It is red hat hosting platform.
- What is OpenShift container registry?
Its an inbuilt storage that is used to store Docker images.
- What is Routes in OpenShift?
In OpenShift Routes is a way to externalize the services by providing externally reachable hostname.In OpenShift routes are created using routers developed by admin.
- What is authentication in OpenShift?
In OpenShift master has inbuilt OAuth server which generates tokens that can be used for API authentication.
- What type of build strategies are used in OpenShift?
- What is Source-to-image Strategy?
In this from source code images are created.In Source-to-image strategy source code is downloaded and compiled and deployed in same container.From same code image is created.
- Define Pods?
It is the collection of containers and its storage.
- What are stateful Pods?
StatefulSets are a Kubernetes feature that enables pods to be stopped and restarted while retaining the same network address and storage attached to them. StatefulSets (PetSets in OCP 3.4) are still an experimental feature, but full support should be added in an upcoming release.
- What are the identity providers in OAuth?
- What is Source-to-image Strategy?
In this from source code images are created.In Source-to-image strategy source code is downloaded and compiled and deployed in same container.From same code image is created.
- What is Deployment Strategies?
OpenShift provides deployment strategies that are defined by each deployment configuration. Each application will have its own requirements for availability and quality of service during deployment. Architectural consideration should be made at design and development time for applications to take into account state (e.g., session state, atomic data—that is, what is the source of truth) and its effects on the quality of business service during updates to the application. For example, an application server that clusters server-side session state will have different concerns than a stateless application that relies on client-side caching only.
OpenShift provides strategies to support a variety of deployment scenarios, which we
will cover in the following sections.
- What is Deployment Pod Resources?
A deployment is completed by a pod that consumes resources (memory and CPU) on a node. By default, pods consume unbounded node resources. However, if a project specifies default container limits, then pods consume resources up to those limits. Another way to limit resource use is to (optionally) specify resource limits as part of the deployment strategy.
- What is blue-green deployments?
The blue-green deployment strategy minimizes the time it takes to perform a deployment cutover by ensuring you have two versions of your application stacks available during the deployment. We can make use of the service and routing tiers to easily switch between our two running application stacks—hence it is very simple and fast to perform a rollback.
- What is Port Binding?
OpenShift ships with a HAProxy-based router which provides ingress routing of HTTP/HTTPS traffic into the running pods. While the main use case is to support web traffic, it is also possible to support non-HTTP traffic (e.g., AMQP) by passing the traffic over SSL and adding the route hostname via the Server Name Indication (SNI) header. It is also possible to integrate existing load/balancing tiers into Open‐Shift.
- What are labels in Open‐Shift?
Labels are identifying metadata consisting of key/value pairs attached to resources. Labels are used to add identifying attributes to objects that are relevant to users and can be used to reflect architectural or organizational concepts. Labels can be used in conjunction with label selectors to uniquely identify individual resources or groups of resources.
- What are Annotations in Open‐Shift?
Annotations are similar to labels but primarily concerned with attaching nonidentifying information, which is primarily used by other clients such as tools or libraries. Annotations don’t have the concept of selectors.
- What is Downward API in OpenShift?
The Downward API is a mechanism whereby pods can retrieve their metadata without having to call into the Kubernetes API. The following metadata can be retrieved and used to configure the running pods:
Pod name, namespace, and IP address
Pod CPU/memory request and limit information
Certain information can be mounted into the pod as an environment variable,whereas other information can be accessed as files within a volume.
- What is Build Configurations?
Builds are configured and controlled by build configuration resources. Build configurations contain the details of the chosen build strategy as well as the source of the developer-supplied artifacts such as Git location, the details of the builder image to be used, and the output image.
- What is SSH authentication?
OpenShift uses the Secure Shell (SSH) network protocol to authenticate your account credentials to the OpenShift servers for secure communication. Successful authentication is necessary to manage your cloud environment, and OpenShift supports both RSA and DSA keys for SSH authentication. This section describes briefly how OpenShift authentication works, and provides information on how to manage SSH keys for OpenShift user accounts.
- How OpenShift works with Docker and Kubernetes?
OpenShift combines the power of Docker and Kubernetes with an enterprise-ready control system. It enables you to create a Continues Deployment Pipeline with all you need from testing to autoscaling.
- What is OpenShift Dedicated?
OpenShift Dedicated is Red Hat’s managed private cluster offering, built around a core of application containers powered by Docker, with orchestration and management provided by Kubernetes, on a foundation of Red Hat Enterprise Linux. It’s available on the Amazon Web Services (AWS) and Google Cloud Platform (GCP) marketplaces.
- OpenShift environment that is running on Amazon Web Services consists of which systems?
When interacting with an OpenShift environment that is running on Amazon Web Services. The environment consists of the following systems:
1 master nodes
1 infrastructure nodes
24 “application” nodes
An NFS server
- What is OpenShift Origin?
OpenShift Origin is a distribution of Kubernetes optimized for continuous application development and multi-tenant deployment. OpenShift adds developer and operations-centric tools on top of Kubernetes to enable rapid application development, easy deployment and scaling, and long-term lifecycle maintenance for small and large teams.
- What are the features of OpenShift Origin?
OpenShift Origin Features:
- Easily build applications with integrated service discovery and persistent storage.
- Quickly and easily scale applications to handle periods of increased demand.
- Support for automatic high availability, load balancing, health checking, and failover.
- Push source code to your Git repository and automatically deploy containerized applications.
- Web console and a command-line client for building and monitoring applications.
- Centralized administration and management of an entire stack, team, or organization.
- Create reusable templates for components of your system, and iteratively deploy them over time.
- Roll out modifications to software stacks to your entire organization in a controlled fashion.
- Integration with your existing authentication mechanisms, including LDAP, Active Directory, and public OAuth providers such as GitHub.
- Multi-tenancy support, including team and user isolation of containers, builds, and network communication.
- Allow developers to run containers securely with fine-grained controls in production.
- Limit, track, and manage the developers and teams on the platform.
- Integrated Docker registry, automatic edge load balancing, cluster logging, and integrated metrics
- What are the benefits of OpenShift Origin?
The benefits available to the developer are numerous:
- Run a PaaS locally on your laptop
- Run a PaaS behind your firewall
- Become a developer on a PaaS and expand your skills and solve interesting technical problems
- Integrate your middleware or framework into an open source PaaS
- Create a new thing based on PaaS technology
- By utilizing an open source IaaS codebase, build a cloud stack using open source
- What can you run on OpenShift?
OpenShift is designed to run any existing Docker images. Additionally, you can define builds that will produce new Docker images using a Dockerfile.
For an easier experience running your source code, Source-to-Image (S2I) allows developers to simply provide an application source repository containing code to build and run. It works by combining an existing S2I-enabled Docker image with application source to produce a new runnable image for your application.
- What are the security controls does OpenShift provide for containers?
OpenShift runs with the following security policy by default:
Containers run as a non-root unique user that is separate from other system users
They cannot access host resources, run privileged, or become root
They are given CPU and memory limits defined by the system administrator
Any persistent storage they access will be under a unique SELinux label, which prevents others from seeing their content
These settings are per project, so containers in different projects cannot see each other by default
Regular users can run Docker, source, and custom builds
By default, Docker builds can (and often do) run as root. You can control who can create Docker builds through the builds/docker and builds/custom policy resource.
Regular users and project admins cannot change their security quotas.
- What are the new features introduced in OpenShift Container Platform 3.7?
OpenShift Container Platform 3.7 significantly expands how we integrate third-party services for our customers, both on-premises and in the cloud. It includes:
The general availability of OpenShift Service Catalog, which includes a new user experience to make it easier for developers to find the runtimes, frameworks, and services they need to be productive.
Access to AWS through the OpenShift platform In OCP 3.7, AWS and OpenShift users will be able to configure and deploy AWS services from within the OpenShift platform, with a single path for support.
- What is OpenShift Cartridges?
Cartridges in OpenShift were the focal point for building applications. Each cartridge provided the required libraries, source code, build mechanisms, connection logic, and routing logic along with a pre-configured environment to run the components of your applications.
- What is Cartridge vs Image?
The easiest replacement term for the cartridge in OpenShift v3 is the image. An image does more than a cartridge from a packaging perspective, providing better encapsulation and flexibility.
But the cartridge concept also included logic for building, deploying, and routing which do not exist in images. In OpenShift v3, these additional needs are met by Source-to-Image (S2I) and templated configuration.
- What is Project vs Domain?
The project is essentially a rename of the domain from OpenShift v2. Projects do have several features that are not a part of domains in OpenShift v2.
- What is Gear vs Container?
The gear and container terms are interchangeable. Containers have a cleaner mapping of being one-to-one with images, whereas many cartridges could be added to a single gear. With containers, the collocation concept is satisfied by pods.
- What is Master vs Broker?
Masters in OpenShift v3 do the job of the broker layer in OpenShift v2. However, the MongoDB and ActiveMQ layers used by the broker in OpenShift v2 are no longer necessary because the key-value store etcd is typically installed with each master.
- What are the features of OpenShift v3?
OpenShift v3 is a layered system designed to expose underlying Docker-formatted container image and Kubernetes concepts as accurately as possible, with a focus on easy composition of applications by a developer. For example, install Ruby, push code, and add MySQL.
- What Are the Layers in OpenShift?
The Docker service provides the abstraction for packaging and creating Linux-based, lightweight container images. Kubernetes provides the cluster management and orchestrates containers on multiple hosts.
OpenShift Origin adds:
Source code management, builds, and deployments for developers
Managing and promoting images at scale as they flow through your system
Application management at scale
Team and user tracking for organizing a large developer organization
Networking infrastructure that supports the cluster
- What are Masters?
The master is the host or hosts that contain the master components, including the API server, controller manager server, and etcd. The master manages nodes in its Kubernetes cluster and schedules pods to run on nodes.
63.What are Nodes?
Nodes – A node provides the runtime environments for containers. Each node in a Kubernetes cluster has the required services to be managed by the master. Nodes also have the required services to run pods, including the Docker service, a kubelet, and a service proxy.
- What are Init Containers?
A pod can have init containers in addition to application containers. Init containers allow you to reorganize setup scripts and binding code. An init container differs from a regular container in that it always runs to completion. Each init container must complete successfully before the next one is started.
- What is Image Version Tag Policy?
Rather than version numbers, the Docker service allows applying tags (such as v1, v2.1, GA, or the default latest) in addition to the image name to further specify the image desired, so you may see the same image referred to as centos (implying the latest tag), centos:centos7, or fd44297e2ddb.
- What Is Canary Deployments?
All rolling deployments in OpenShift Origin are canary deployments; it checks a new version (the canary) before replacing all the old instances. Unless the readiness test never works, then the canary instance and deployment will be disabled.
- What Is Routes In Openshift?
In OpenShift Routes is a way to externalize the services by providing externally reachable hostname. In OpenShift routes are created using routers developed by admin.
- Explain difference between Openshift and Openstack?
Both OpenStack and OpenShift Origin are open source projects, and both provide cloud computing foundations. However, they do not compete with each other. OpenStack provides “Infrastructure-as-a-Service”, or “IaaS”. It provides bootable virtual machines, networking, block storage, object storage, and so forth.
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