OpenStack Interview Question & Answer

OpenStack Interview Question

If you’re looking for OpenStack Interview Questions for Experienced or Freshers, you are at right place. There are lot of opportunities from many reputed companies in the world. According to research OpenStack has a market share of about 0.7%. So, You still have opportunity to move ahead in your career in OpenStack Engineering.

1. What are the key components of OpenStack?

Horizon: the only GUI in OpenStack; the first component administrators see and get an idea of the current operations in the cloud.
Nova: chief computing engine to handle multiple virtual machines and computing tasks
Swift: reliable and robust storage system for files and objects helping developers to refer to a unique identifier and Openstack decides where to store the info.
Cinder: similar to traditional computer storage system, it is a block storage system in OpenStack for accessing files at faster speed.
Neutron: ensures efficient connectivity between components during deployment.
Keystone: a central identity list of all OpenStack cloud users and provides various mapping techniques to access methods against Keystone.
Glance: image service provider where images are the virtual copies of hard disks. Allows using the images as templates during deployment of new instances.
Ceilometer: component providing billings services and other telemetry services to cloud users. Maintains an account of component system usage by each user.
Heat (Orchestration Engine): Allows developers to orchestrate/illustrate and store the cloud application requirements and resources needed in a file, thereby maintaining the cloud infrastructure.

Read More: OpenStack Command Line Cheat Sheet

2. What storage types are allowed by OpenStack Compute?

OpenStack Cloud Operating system supports two types of storage:
Persistent Storage: Persistent and independent of any particular instance, created by users. This further includes three storage:

Object storage: to access binary objects through the REST API.
Block storage: offers access-to-block storage devices by affixing volumes their current VM instances.
Shared File System storage: provides a set of services to manage multiple files together for storage and exchange with multiple users at one time.
Ephemeral Storage: Referring to a single instance. As the name suggests, these storage options are temporary and short-lived and disappear once the VM is terminated.Interested in a high-paying career in Cloud Computing?

3. Define ‘users,’ ‘role’ and ‘tenant’ in OpenStack.

Users can be members of multiple projects:
Tenant is a group of users and an alternative term for Project/accounts where projects are organizational units in cloud processing
Role is the position to which a user is mapped (the authorization level). Roles are usually assigned to project-user duos.

4. Define the Networking Managers in OpenStack Cloud.

Flat Network Manager: This places all VMs on a single network utilizing the same subnet and bridge as created by the administrator. Thus, all VMs share the same network that can be interconnected and are known to have Flat Network Manager.

Flat DHCP Network Manager: Much similar to the above except that the IP addresses to VM are assigned via DHCP (Dynamic Host Configuration Protocol).
VLAN: Unlike the single network concept, VLAN facilitates more secure and separate network to VMs. It has a physical switch to offer separate virtual network and separate IP range and bridge for each tenant. This is indeed most preferable choice for multi-tenant/project environment.

5. Define Identity Service in OpenStack.

Keystone is the most important and preferred Identity Service in OpenStack and executes the complete OpenStack Identity API. The Keystone Identity Service is responsible for user management and service catalog. In user management, it tracks users and their permissions while Service Catalog offers a list of services available with their API. The former provides authentication credential details of users, tenants and roles.
Internal services like Token and Policy are also part of Keystone Identity

6. Name the commands used to pause and un-pause(resume) an instance

# novaunpause INSTANCE_NAME
# nova pause INSTANCE_NAME

7. List the storage locations for VM images in OpenStack

• OpenStack Object Storage
• Filesystem
• S3
• RBD or Rados Block Device
• GridFSMaster Openstack from industry experts. Find out more in this openstack Blog now.

8. What is OpenStack Python SDK?

Python SDK (Software Development Kit) helps users to write applications for performing automation tasks in Python by calling Python objects. It provides a platform to work with multiple OpenStack services at one place. It consists of language bindings to access OpenStack clouds, complete API reference, easy interaction with REST API and sample code for initial applications.

9. Describe the function of Filter Scheduler.

The Filter Scheduler facilitates filtering and weighting to notify where a new instance can be created. It supports working with Compute Nodes. Filter Scheduler firstly creates an unfiltered dictionary of hosts and then filter them using related properties and makes the final selection of hosts for the number of instances as needed.

10. Define the Networking option in OpenStack.

– AvalabilityZoneFilter: filters hosts by their availability zone.
– CapacityFilter: filtering based on volume host’s capacity consumption
– DifferentBackendFilter: Scheduling volumes to a different back-end
– DriverFilter: filters based on ‘filter function’ and ‘metrics’
– InstanceLocalityFilter
– JSONFIlter
– RetryFilter: Filter the previously attempted hosts
– SameBackendFilterMost in-depth, industry-led curriculum in Openstack.

11. List down the type of Hypervisors supported by OpenStack.

KVM (Kernel-based Virtual machine)
LXC: Linux Containers having Linux-based VMs
QEMU: Quick EMUlator used for development purposes
UML: User Mode Linux used for development purposes
VMware vSphere: VMware-based Linux and Windows via vCenter server connection.
Hyper-V: Server virtualization with Microsoft’s Hyper-V

12. Explain in brief the modular architecture of OpenStack.

The three important components of OpenStack modular architecture are:

OpenStack Compute: For managing large networks on the virtual machine
Image Service: The delivery service provides discovery and registration for virtual disk images
OpenStack Object Storage: A storage system that provides support for both block storage and object storage

13. What command manages floating IP addresses in OpenStack

nova floating-ip-*

14. List down the components of OpenStack Compute

Nova (Compute) Cloud comprises following components:

– API server
– Message Queue (Rabbit-MQ Server)
– Compute Workers (Nova-Compute)
– Network controller (Nova-Network)
– Volume Worker
– Scheduler

15. Define the role of API Server.

It provides an interface for the external world to interact with the cloud infrastructure.

16. Define Flavor

Flavors are virtual hardware templates present in OpenStack, which define the memory sizes of RAM, hard disk, etc. Flavors illustrate a number of parameters like ID, Name, Memory_MB, Disk and others, giving a choice of Virtual Machine to the user just like having a physical server. OpenStack dashboard also allows users to modify a flavor by deleting the existing one and creating a new with the similar name and parameters.

17. How to create a user in OpenStack?

# nova-manage user create user-name

18. What is the meaning of term “Cinder” in OpenStack service?

For handling persistent storage for virtual machines, OpenStack provides the service referred as Cinder. There are multiple backends for cinder. The one that is utilized by default is LVM, called Cinder-Volumes.

19. Explain what is Cells in OpenStack?

Cells functionality enables you to scale an OpenStack Compute cloud in a more simplistic way. When this functionality is enabled, the hosts in an OpenStack Compute cloud are partitioned into group called cells. Cells are configured as trees.

20. Explain how you can transfer volume from one owner to another in OpenStack?

You can transfer a volume from one owner to another by using the command cinder transfer*.

21. What is bare-metal node and what does it comprised of?

It gives access to control bare metal driver, through which you can control physical hardware resources on the same network.

Bare metal node is comprised of two separate components

– Bare metal node Orchestrator: It’s a management software, which acts as a dispatcher to all nodes in the cluster.
– Bare metal node Operating System: It is a base software, which runs on each node in the cluster.

22. What are functions of “Nova”?
– Instance life cycle management
– Management of compute resources
– Networking and Authorization
– REST-based API
– Asynchronous eventually consistent communication
– Hypervisor agnostic : support for Xen, XenServer/XCP, KVM, UML, VMware vSphere and Hyper-V

23. What are functions and features of Swift?

– Storage of large sized objects
– Storage of large number of objects
– Data Redundancy
– Archival capabilities – Work with large datasets
– Data container for virtual machines and cloud apps
– Media Streaming capabilities
– Secure storage of objects
– Extreme scalability
– Backup and archival

24. Give an example where logs help in OpenStack security?
For instance, analyzing the access logs of Identity service or its replacement authentication system would alert us to failed logins, frequency, origin IP, whether the events are restricted to select accounts and other pertinent information. Log analysis supports detection.

25. What is sanitization process?
The sanitization process removes information from the media such that the information cannot be retrieved or reconstructed. Sanitization techniques, including clearing, purging, cryptographic erase, and destruction, prevent the disclosure of information to unauthorized individuals when such media is reused or released for disposal.

26. What is job of user CRUD?
The user CRUD filter enables users to use a HTTP PATCH to change their own password

27. Where caching configuration is stored?
The majority of the caching configuration options are set in the [cache] section of the keystone.conf file.

28. How you can change behavior of DHCP server?
The behavior of dnsmasq can be customized by creating a dnsmasq configuration file

29. What is use of account reaper?
In the background, the account reaper removes data from the deleted accounts.

30. What you will do in case of server failure?
If a server is having hardware issues, it is a good idea to make sure the Object Storage services are not running. This will allow Object Storage to work around the failure while you troubleshoot OpenStack.
If the server just needs a reboot, or a small amount of work that should only last a couple of hours, then it is probably best to let Object Storage work around the failure and get the machine fixed and back online. When the machine comes back online, replication will make sure that anything that is missing during the downtime will get updated.
If you cannot replace the drive immediately, then it is best to leave it unmounted, and remove the drive from the ring. This will allow all the replicas that were on that drive to be replicated elsewhere until the drive is replaced. Once the drive is replaced, it can be re-added to the ring.