OpenShift Interview Questions

What is Openshift?

OpenShift is a cloud-based platform as a service which is hosted by Red Hat. It is an open-source that helps organizations to shift their traditional application platform and infrastructure from virtual and physical mediums to the cloud. Openshift supports an enormous number of different applications that can be developed and deployed easily on the OpenShift cloud platform.

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List some features of Openshift?

Open Shift supports a number of different features:

• Openshift has an extensive command-line toolset
• Multiple languages and database support
• Supports remote SSH login to the application
• Supports for continued integration and version management
• Self-service of Demand Application Stack
• One-Click Deployment
• Built-in Database Services
• Extensible Cartridge System
• Rest API Support
• Multi Environment Support
• Automatic Application Scaling
• Standardized Developers' workflow
• Remote Debugging of Applications
• Responsive Web Console
• Rich Command-line Toolset
• IDE Integration

How does Docker differ from OpenShift?

The main difference between Docker and OpenShift is that Docker focuses exclusively on the execution container is a project, whereas OpenShift includes both the execution container and the REST API, web interfaces, and coordination for deploying and handling individual containers. OpenShift is more of an abstraction layer to orchestrate containers. OpenShift uses internal Kubernetes to orchestrate containers. To orchestrate containers, Docker has a swarm of dockers to orchestrate containers.

What does OpenShift deployment mean?

In Openshift, deployment is a controller depending on the user-defined template known as deployment configuration. Deployments are created manually or as a result of triggered events. The deployment system consists of the following: 

• A deployment configuration that is a deployment template.
• Triggers which result in automatic deployments in response to the events.
• User customizable strategies to transition between previous deployment and the new deployment.
• Manually scaling replication.
• Previous deployment rollbacks

What are deployment Strategies?

A deployment strategy is a way by which an application can be modified or upgraded. The purpose is to do the change without downtime so that the user hardly notices the enhancements. A common strategy involves using a blue-green deployment. The new version is tested and evaluated, whereas users continue to use the stable version. When they are ready, they can switch to a blue version.

What do you mean by rolling deployments?

Rolling deployment replaces the application's previous version instances with the application's new version instances. A rolling deployment generally requires new pods to be ready through a readiness check prior to reducing the size of older components. In the event of any significant problem, rolling deployment may be interrupted.

What do you mean by canary deployment?

In OpenShift Origin, All rolling deployments are the canary deployments; and a new version is tested prior to all old instances being replaced. If the readiness check is not successful, the canary instance will be removed, and the deployment will proceed.

What is gear?

A Gear in Openshift is a server with certain conditions such as memory, CPU, etc. Also, Openshift calls it isolated or separated clusters. They are mainly liable for the application’s working. Besides the software product, the application is largely executed by Gears. 

Define routes and Services.

As pod consists of containers and services, the service in Openshift is a set of logical pods. In Openshift, the service is assumed to be a REST object. In Openshift, Routes are used for analyzing and externalizing services that are in effect or necessary to reach the hostname externally. This is accomplished with the help of the routers developed by the admin commands.

) What is the difference between Openshift and Openstack?

OpenStack and OpenShift Origin both are open source projects, and both of them provide cloud computing basics. But they don't compete against one another. OpenStack comes with "Infrastructure-as-a-Service". It delivers networking, bootable virtual machines, object storage, block storage, etc.

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) What is Openshift Security?

OpenShift security is primarily a combination of two components which deal primarily with security constraints.

Security Context Constraints: Generally, Security Context Constraints are used for pod restriction that defines the limits of a pod, like what all the actions it can perform and what can be accessed within the cluster.

Service Account: The primary purpose of service accounts is to control access to the OpenShift master API, that is invoked when a request or command is initiated from any node or master machine.

) Explain feature toggles.

Feature toggles are the techniques which help to include both new and old versions of a feature into the same code database. But the versions are surrounded by the execution logic or depending on the factors like database switch or the property value. The feature toggles make it possible to separate the deployment of the use, of a single group, of the old systems, and of several groups of servers.

) What is the Openshift Pipeline?

With OpenShift Pipelines, you can control the development, deployment, and promotion of your applications through OpenShift. With the help of Jenkins files, Jenkins Pipeline Build Strategy, and OpenShift domain-specific language that is provided by OpenShift Jenkins client Plugin You are able to create the advanced building, testing, deployment, and promotion pipelines for any scenario.

) What are the types of Security controls in OpenShift?

There are precedents for OpenShift's security policy. Containers were unable to access host resources or execute preferred operations. Containers should be executed separately from other users as unique non-root users. Containers obtain memory and CPU limits based on system admin definitions. More importantly, the security quotas could not be changed by regular users or administrators.

) What are the benefits of OpenShift origin?

Benefits include the local execution of PaaS on a system and in the back of a firewall. OpenShift Origin helps improve developer skills with PaaS and broadening competencies.

) What is an Openshift cartridge?

OpenShift cartridges are key points in application development. Each cartridge is provided with build mechanisms, specific libraries, routing logic, source code, and connection logic with a preconfigured environment. All of these factors contribute to the execution of your application.

) What does the OpenShift Container Platform include?

RedHat OpenShift Container Platform is a Platform as a Service product of RedHat, officially called as OpenShift Enterprises. This is a supported Kubernetes distribution that uses Docker containers and DevOps tools to accelerate application development. OpenShift has a completes of open source programming languages that allow developers to choose between multiple languages. Open Shift also enables us to have highly available applications with auto-scaling and self-healing with no manual configuration that should normally take place in a traditional environment, both on-site and in the public cloud.

) What is OpenShift CLI?

The OpenShift CLI tool can be used to manage OpenShift applications through the command line. The OpenShift CLI enables us to manage the life cycle of the application from end to end. It provides basic and advanced configuration features of the applications. It also contains features for managing, deploying and adding applications.

) Explain Blue/green deployments.

The Blue/Green deployment is a strategy that minimizes the required time to complete a deployment transfer by making sure that we have two versions of the application stacks available while deployment. To easily switch between two running application stacks, we can use service and routing tiers. Therefore, it is very easy and quick to carry out a rollback.

) What are Stateful pods?

To stop and restart the pods, we use StatefulSets, a feature of Kubernetes that keeps their storage and network address unbroken. But still, the StatefulSets are in the beta feature or trial period, which will be turned to support completely in its upcoming versions.

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) What is Haproxy?

If our application is scalable, then HAProxy will accept all the incoming connections. It analyzes the HTTP protocol and determines to which instance of the application the connection is to be routed. That's important because it enables the user to get sticky sessions.

) How gear differs from the container?

Both the words "gear" and "container" are interchangeable. The containers are accurately mapped using one to one relations between the images. However, for gears, numerous cartridges may form part of one gear. For containers, pods carry out the collocation concept.

) What do you mean by Application Scaling?

In the OpenShift application, auto-scaling is also referred to as pod auto-scaling. Two kinds of application scaling are available:

Vertical Scaling: To meet a higher load with vertical scaling, the application stays in the same place where you provide it with more resources. For instance, you can add a bigger machine with faster CPUs, more CPU, memory or disk space. The cost continues to increase with the addition of hardware resources.

Horizontal Scaling: To allow a higher load with the help of horizontal scaling, several instances of an application are created, and application load is distributed among independent nodes.

With the expansion of the user base, the load and demand for applications increases. To maintain this demand, we need either horizontal scaling or vertical scaling.

) What is Openshift Online?

OpenShift online is the OpenShift community service that enables the rapid creation, deployment and expansion of containerized applications in the public cloud. This is the platform for development and hosting by Red Hat's public cloud platform, that allows automated provisioning, application scaling and management to assist developers in focusing on the development of the framework logic.

) What is Downward API?

The Downward API is a mechanism by which pods can fetch their metadata without the need for the Kubernetes API. Following is the metadata that can be recovered and used for configuring the running pods: 

• Annotations
• Labels 
• Information related to Pod CPU/memory request and limit
• Namespace, Pod name, and IP address
• Some information can be set up in the pod as an environment variable, while other information is accessible as files in a volume.

) Why Docker and Kubernetes in Openshift?

Docker assists in the creation of lightweight liner-based containers, whereas Kubernetes assists in the orchestration and management of containers. OpenShift runs over Docker and Kubernetes. All the containers are built over the Docker cluster, that is essentially the Kubernetes service over Linux machines, with the help of the Kubernetes orchestration feature. In this process, we build a Kubernetes master that controls all nodes and will deploy containers across all nodes. Kubernetes' primary purpose is to control the OpenShift cluster and deployment flow with a different configuration file. Like in Kubernetes, we use kubctl. Similarly, we use the OC command-line utility for developing and deploying containers on the cluster nodes.

) What is Volume Security?

Volume security signifies securing the PVC and PV of projects within the OpenShift cluster. There are mostly four sections for controlling volume access within OpenShift. 

• runAsUser
• fsGroup
• seLinuxOptions
• Supplemental Groups

) Explain labels in Open-shift.

) What is the source-to-image strategy?

Source-to-image strategy is used to create source code images. This is achieved by downloading and compiling the same container. The images are created according to the same code. Within the customized strategy, jar and rpm are created.

Related Article: Openstack Training 

) Why choose Openshift?

OpenShift offers a common platform for business units to host their applications in the cloud irrespective of the underlying operating system. This makes the use, development and deployment of applications in the cloud extremely easy. A major feature is that it offers network resources and managed hardware for all sorts of development and testing. With OpenShift, the PaaS developers are free to design the environment they need with specifications.

) What platforms does OpenShift support?

There are three different platforms that Openshift supports-

• IaaS- Infrastructure-as-a-Service
• PaaS- Platform-as-a-Service
• SaaS- Software-as-a-Service

) Name the primary components of OpenShift architecture.

The following are the significant components of Openshift:-

• Kubernetes Master Machine Components: API Server, Controller Manager, Etcd, and Scheduler. 
• Kubernetes node components: It consists of Docker, Kubernetes proxy service, and Kublet service.

) Define SSH Authentication in OpenShift.

SSH or Secure Shell network protocol used by OpenShift, which authenticates the user account credentials. It helps to communicate with OpenShift servers securely. Further, OpenShift supports both SA and DSA keys for this authentication. Hence, authentication is essential to manage your cloud environment.

) What is the network plugin that connects pods across the cluster?

 The network plugin “ovs-subnet” offers connectivity for pods across the cluster.

) Define OAuth Server.

OAuth Server is an in-built feature of the master structure in OpenShift. It is helpful to produce tokens that help to authenticate the API. OAuth exists in the default setup of the master structure. 

The following are the various types of identity providers that exist in the OAuth Server.

• Allow All
• LDAP
• Deny All
• htpasswd
• Basic Authentication.

) What is meant by OpenShift Dedicated

OpenShift Dedicated is a complete Openshift container platform and a cloud service helpful in creating and deploying container applications. It is mainly configured for high availability and dedicated to only a single customer. Moreover, OpenShift Dedicated is a wholly managed Red Hat OpenShift service.

Conclusion:

All the above are some of the frequently asked Openshift Interview questions. They are most likely to be asked in your interview. Learning these questions may give you confidence in Openshift. Hopefully, you'll be successful in your interview. All the best for your interview.

fine Annotations in OpenShift.

Ans. An Annotation in OpenShift is similar to a label and is a key-value pair. There are two segments of a valid annotation key: a Prefix (optional) and a Name, and a “/” slash separates them. Further, annotations can be added to a function. 

) Briefly explain the OpenShift v3 features.

Ans. The OpenShift v3 is a layered system developed to reveal underlying container images that are Docker-formatted and the concepts of Kubernetes correctly by concentrating on the easy application composition by a developer.