Today we are going to discuss top VMware interview questions and its answers mostly asked in any VMware interview duration. This will help freshers. Let us know about your feedback once it is useful for you. We have collected these questions and answers based on our own experience because we have given so may interview for VMware admins with selection.
This blog is very basic and contains basic questions or I would say not for super tech guy working with VMware technology for years. We have planned another blog dedicated to advanced users and will write soon. We would assume that any reader coming here would have completed any beginners’ course on VMware and preparing for interviews.
VMware Interview Questions And Answers
VMware is a technology company based in Palo Alto, California, the United States that provides well-known virtualization software and cloud computing services. VMware’s major software products are VMware ESXi, VMware vSphere, VMware vCenter Server, VMware Horizon, and VMware Cloud Foundation services for Cloud Computing. VMware shares ~80.7% of the market in software virtualization, as per the IDC report.
VMware provides virtualization services through VMware ESXi software. ESXi stands for Elastic Sky X Integrated is an enterprise-class server virtualization platform. ESXi is a type-1 hypervisor.
VMware virtualization software helps us to reduce the number of server hardware in the data centers. We can have multiple virtual machines on single physical server hardware. It shares the resources(such as CPU, Memory, and Storage) among the virtual machines. It also reduces the IT cost by reducing the number of the hardware. It also simplifies the provisioning and management of IT infrastructures.
VMware hypervisor is an application program that enables us to run multiple operating systems on single physical server hardware. It shares resources such as CPU, Memory, and Storage and manages its allocation between the virtual machine that runs on an Operating System. The hypervisor manages the resource sharing and allows the VMs to run independently without affecting each other.
There are two types of hypervisors available in the market:
Type 1 Hypervisor – This is known as Bare metal or native hypervisor. It works directly on the hardware of the host and can monitor the operating system that runs above the hypervisor. It is also completely independent of the operating system. Example: VMware ESXi Servers, and Citrix/Xen Servers.
Type 2 Hypervisor – This is known as Hosted Hypervisor. In this, the hypervisor is installed on an operating system and then supports other guest operating systems above it. It is completely dependent on host OS for its operation. Example: VMware workstation, Oracle virtual box
a) Application Virtualization
b) Compute Virtualization
c) Network Virtualization
d) Storage Virtualization
e) Data Virtualization
VMware ESXi is virtualization software. VMware ESXi stands for Elastic Sky X Integrated. It is a type-1 hypervisor that can be installed directly onto the physical server. We can build and deploy virtual machines on the top of en ESXi software. The latest release version of this software is ESXi 7.0
Please find below the details:
VMware vSphere is VMware’s virtualization platform. It includes resources like CPU, Memory, Networking, and Storage and aggregates these resources in a single entity. It also provides you the tools to manage the virtual environments. We can say it as a VMware vSphere suite. The two core components of vSphere are ESXi and vCenter Server.
vCenter Server allows IT administrators to deploy, manage, monitor, automate, and
secure a virtual infrastructure in a centralized way. vCenter Server is also meant to
provide a centralized management platform and framework for all ESXi hosts and their respective VMs. We can have multiple data centers in a single vCenter Server.
A virtual machine is a software computer that like a physical computer, runs an operating system and applications. The virtual machine runs on the host and that host may contain many isolated virtual machines.
An operating system installed on a virtual machine is called guest operating system. OS could be either Windows or Linux based.
There are many ways to deploy a virtual machine-
1. Use CD-ROM/ISO image file.
2. Use a template to create a virtual machine
3. Deploy virtual machines using the OVF/OVA file.
4. Use Clone to new VMs
Hot-plug is a feature in a virtual machine setting. If this is enabled then you can increase the resources on the fly without shutting down the virtual machine. If disabled then you have to shut down the VMs and enable it. Hot-plug works for both CPU and Memory.
Virtual Machines are collection of many files such as-
• .vmx – Virtual machine configuration file
• .vmdk – Virtual disk characteristics
• -flat.vmdk – Virtual machine data disk
• .nvram – Virtual machine BIOS or EFI configuration
• .vmsd – Virtual machine snapshots
• .vmsn – Virtual machine snapshot data file
• .vswp – Virtual machine swap file
• .log – Virtual machine log file
• .vmtx – Created when you convert a virtual machine to a template
The Snapshot is a point-in-time image of a virtual machine. Snapshots preserve the state and data of a virtual machine. A snapshot contains the following data:
– VM configuration files such as RAM/CPU
-The power state of the virtual machine
-State of all the virtual machine’s virtual disks.
There are many limitations to the snapshot of a virtual machine.
-VMware does not support snapshots of raw disks, RDM physical mode disks.
-Snapshots are not supported with PCI vSphere DirectPath I/O devices
-Quiesced snapshots require VMware Tools installation and guest operating system support
-VMware does not support snapshots of virtual machines configured for bus sharing
-Snapshots can negatively affect the performance of a virtual machine
-If a virtual machine has virtual hard disks larger than 2 TB, snapshot operations can take much longer to finish
Max 32 at a time.
First things check whether you have enough free space in the data store to store the snapshot files. Now check whether virtual machines have any RDM or not because with RDM snapshot is not possible. Also, check for any attached CD-ROM/ISO media.
Sometimes creating multiple snapshots generate redundant delta disks which may affect the virtual machine’s performance. We use the consolidation of VMs. After consolidation, redundant disks are removed, which improves the virtual machine performance and saves storage space.
Navigate to a virtual machine in the vSphere Web Client inventory.
Go to Action -> Snapshot -> Consolidate
When you click on the Consolidate then a dialog box appears.
You may try to reset the virtual machine power option and let it reboot. You may also try to disconnect and connect the NIC card from the virtual machine setting. But before doing it all take necessary approval from your management.
I will go through with the simple steps on how to increase the disk space of the windows server without rebooting it.
First, Go to the vCenter and search for the virtual machine. Either right-click on VM or click on the Action button. Select the Edit Settings options from the drop-down menu. It will open a new window containing VM’s related information. Expand the Hard disk menu. You will see all the hard disks present in the server. Now select the disk number you want to expand. It will show you the options to increase the disks either in MB or GB you can increase it. Click ok.
You have done the vCenter part now login to the server and open disk management console by typing diskmgmt.msc on command prompt. Rescan the disks from the console. After rescanning done you will be able to see free space next to the volume increased earlier. Right-click on the volume and choose the option to expand the size.
This way you can increase the disk space of windows servers. In the case of the Linux server, after increasing the space from vCenter request the Linux team to expand the file system from their end.
Yes. To take effect of new name you have to restart it once.
vDisk is called a virtual disk attached with the virtual machine. Similarly a vCPU is known as virtual CPU and vRAM is known as virtual RAM assign to a virtual machine.
Whenever we need to do any kind of activity on a live environment’s host then we put the host in maintenance mode. It will migrate all the VMs from the host to another host if it a part of cluster and DRS is set to fully automatic otherwise shut down all the VMs before entering in maintenance mode. After that, we can do whatever changes we want to do with the host. It would not affect other hosts in the cluster.
VMware tools are the additional software utility that you can install in a virtual machine running on ESXi. VMware tools contain additional drivers that provide better control over Virtual machines including drag-and-drop feature, time sync between machine to host, and network drivers to have smooth connectivity with host networking. It also solves the problem of Low Video resolution, Incorrect display of network speed, Restricted movement of mouse, and Missing sound
Raw device mapping (RDM) is a feature in the VMware server virtualization environment that enables a storage logical unit number (LUN) to be directly connected to a virtual machine (VM) from the storage area network. RDM provides better IOPS services.
Mostly we use RDM for Microsoft Clustering because it provides faster IOPS(input-output per second). It also better enables scalable backup offloading systems.
Two compatibility modes are available for RDMs:
I) Virtual compatibility mode allows an RDM to act exactly like a virtual disk file, including the use of snapshots.
II) Physical compatibility mode allows direct access of the SCSI device for those applications that need lower-level control.
NAA stands of Network Address Authority and LUN stands for Logical Unit Number.
NAA ID’s are unique alpha-numeric numbers assign to the datastore and RDM devices. A small part of physical disks allocated by Storage end called LUN and presented to the ESXi host.
RAID stands for Redundant Array of Independent Disk. In RAID we configure multiple disk to present a single unit of storage.
RAID 0, RAID1, RAID 2, RAID 5, and RAID 10. These are widely used.
For more details visit the Wiki.
The Direct Console User Interface (DCUI) allows you to interact with the host locally using text-based menus.
ESXi PSOD stands for Purple Screen of Death). The ESXi console shows PSOD when there is any critical hardware failure that occurs with the ESXi. In this case, we first reboot the host and then we put the host in the maintenance mode and start our troubleshooting either with VMware or with the Data Center operation guy. For more troubleshooting visit KB article.
A VMkernel networking interface provides network connectivity for the host as well as handling VMware vMotion, IP storage, and Fault Tolerance. You can create VMkernal adaptors to handle the various traffic.
iSCSI stands for Internet Small Computer Systems Interface. ESXi systems include iSCSI technology to access remote storage using an IP network. iSCSI is a protocol that uses the TCP to transport SCSI commands, enabling the use of the existing TCP/IP networking infrastructure as a SAN.
ESX is the older version of VMware virtualization software. ESX is deprecated. ESXi is the new virtualization software currently being used widely. ESX has a service console to manage it but ESXi does not have the service console, It uses DCUI for the same.
VMware vMotion enables the live migration of running virtual machines from one physical server to another with zero downtime, continuous service availability, and complete transaction integrity. VMotion is a key enabling technology for creating the dynamic, automated, and self-optimizing data center.
In storage vMotion, you can move a powered-on virtual machine to another host along with its storage. But if it is in shared storage then no need for the svMotion.
ILO(Integrated Lights Out) and iDRAC are used to manage the ESXi hosts. You can check the logs, take the console and update the system firmware using ILO/iDRAC. ILO is use for HPE servers and iDRAC is use for DELL servers.
VUM stands for VMware Update Manager. Using VUM, you can upgrade the ESXi directly through the vSphere web clients.
Grouping multiple ESXi hosts together are known as VMware clustering. We need at least two hosts to create the cluster of the same configuration. The maximum number of hosts can be in a cluster is 64. It has features like HA and DRS.
HA stands for High Availability. In VMware vSphere HA automatically restart the virtual machines on another host in case of a host failure or host isolation. This way you can ensure the high availability of your mission critical applications. In HA, VM goes down and in FT VM does not go down during fail over.
DRS stands for Distributed Resource Scheduler. DRS provides scheduling and load balancing across a vSphere Cluster and ensure the availability of resources.
DRS is three types:
I) Fully Automated– In the fully automated approach, DRS applies both the initial placement and load balancing recommendations automatically.
II) Partially Automated– With partial automation, DRS applies recommendations only for initial placement of VMs.
III) Manual– In manual mode, you must apply the recommendations for both initial placement and load balancing recommendations.
Admission control is a policy used by VMware HA to ensure failover capacity within a cluster.
Hyperthreading is an Intel-proprietary technology used to enable a core to appear as two logical processors to the ESXi. Hyperthreading enables the processor to run two independent applications at the same time on each processor core. Hyperthreading is enabled by default on systems that support it otherwise you can enable it.
EVC stands for Enhanced vMotion Compatibility used in cluster. EVC ensures vSphere vMotion compatibility. EVC created a baseline of CPU ID for all the hosts within the cluster.
VMware vSphere FT stands for Fault Tolerance. FT provides continuous availability for your applications by creating a live shadow instance of a virtual machine that mirrors the primary virtual machine. If a hardware outage occurs, vSphere FT automatically triggers failover to eliminate downtime and prevent data loss. FT uses FDM(Fault Domain Manager) technology to identify and failover of virtual machine.
Affinity rules and anti-affinity rules tell the vSphere hypervisor platform to keep virtual machines together or separated. You can set affinity rule to keep a virtual machine stick with a hypervisor by applying affinity rules. Similarly you can apply anti-affinity rules to keep away a VM from a host.
While setup vSphere HA you set the VM restart priority or Host isolation response for a VM in the cluster. You can override these rules by applying DRS override rules for the particular VM.
Go to cluster->Configuration->VM overrides->Add rule
An ESXi release version that contains an image of VMware ESXi Server and additional components such as drivers and adapters that are necessary to bring up a server. The firmware provides the capability of ESXi software to communicate with the server hardware. To keep server healthy, you should have the latest version of firmware installed in your system.
Multi-pathing is a technique that lets you use more than one physical path for transferring data between the ESXi hosts and the external storage device. There are three paths used:
I)Most Recently Used (MRU) – The MRU policy selects the first working path, discovered at system boot time. This is the default pathing policy used by LUN.
II) Fixed (Fixed) – The FIXED policy uses the designated preferred path flag if it is configured. It works as you configure it.
III) Round Robin (RR) – The RR policy uses an automatic path selection, rotating through all available paths, enabling the distribution of load across the configured paths.
A network of physical machines that are connected so that they can send data to and receive data from each other. VMware ESXi runs on a physical machine and a physical network.
A network of virtual machines running on a physical machine that are connected logically to each other so that they can send data to and receive data from each other. Virtual machines can be connected to the virtual networks that you create when you add a network.
VMware vSphere Standard Switch works for virtual machine much like a physical ethernet switch. A vSphere standard switch can be connected to physical switches by using physical Ethernet adapters, also referred to as uplink adapters.
A VMware vSphere distributed switch acts as a single switch across all associated hosts in a data center to provide centralized provisioning, administration, and monitoring of virtual networks.
Network services connect to switches through port groups. Port groups define how a connection is made through the switch to the network. You can have multiple port groups on a single standard/distributed switch.
When we add multiple uplink adapters with a single switch to form a team that will help on load-balancing and high availability for network traffic.
VLAN stands for virtual LAN. VLAN enable a single physical LAN segment to be further segmented into parts.
The VMkernel networking layer provides connectivity to hosts and handles the standard infrastructure traffic of vSphere vMotion, IP storage, Fault Tolerance, and vSAN.
There are two types of network services available in ESXi.
I) Virtual Machine Network – It Connects virtual machines to the physical network and virtual machine to another virtual machine.
II) VMKernal – It connects VMkernel services (such as NFS, iSCSI, or vMotion) to the physical network.
Standard vSwitch works similar as physical switch. You can say it a virtual switch and create port groups on it. You can see vSwitches from-
Configure -> Networking -> Virtual Switch -> vSwitch0
ESXi creates a default switch vSwitch0 when you first install it.
You can add three types of network adapter to an ESXi.
I) VMKernal Network Adapter – It handles traffic for ESXi services such as vMotion, iSCSI, NFS, and Fault tolerance.
II) Virtual Machine Port Group Network adapter – A port group that handles traffic of virtual machine on a vSphere standard switch.
III) Physical Network adapter – A physical network adapter handles the traffic of ESXi host on the physical network.
MTU (Maximum Transmission Unit) tells the capacity of a standard switch on how much it can transfer the data at one time. The default MTU for a vSphere switch is 1500 Bytes.
The communication between two ESXi host is known as FT logging when you configure FT between them.
When you migrate powered off VMs that is called cold migration and when you migrate power on VMs that is called hot migration.
DataCenter in a VMware vSphere is a container and inventory of various virtualized objects such as ESXi, VMs and Other files.
Yes. Using Enhanced vMotion you can migrate VMs between two DCs. Most probably you have to just down the VMs before migrating them.
NFS stands for Network file system. NFS is a file sharing protocol which ESXi host used to communicate with the NAS(Network attached device).
This is virtual machine file system used by VMware for storing virtual machine related files in datastore. VMFS is more robust, and resilience than other file system for VMware environment.
Please find below the details:
First of all vCenter server comes with native high availability features but due to some reason your vCenter server goes down then FT and HA will continue to work but services like DRS will not work because it requires vCenter services to work properly. vCenter server requires only when configuring FT and HA.
VMWare SRM stands for the site recovery manager. SRM helps users to keep running their virtual environment on Site B if Site A fails. We have to configure it between Site A & Site B for SRM. SRM reduces the downtime on the systems and make sure of the high availability of applications.
HA is configured per cluster and FT is configured per VM basis. In HA, VM goes down during failover and In FT, VM does not require downtime during the failover.
There are three types of disk used in VMware vSphere.
I) Thick Provision Lazy Zero – Physical space is allocated to a VM while creating Virtual Disk. It can not be converted to thin provisioning disk once in thick pro lazy zero.
II) Thick Provision Eager Zero – This disk type is used specifically in VMware Fault Tolerance(FT) and high I/O. The disk space is allocated to a VM at the time of creation and it takes more time to create a virtual disk.
III) Thin Provision – In thin provisioning, It allocates disk space on-demand to VMs and grows.
I) Network Heartbeat
II) Datastore Heartbeat
For this purpose, you have to install VMware standalone converter in your physical machine. You must have at least one vCenter server to export and import the VM to it. This process is also known as P2V. You can download the application here.
The .nvram files contain information about system BIOS. You can recover it by rebooting your machine. It will automatically create the new .nvram files during the boot process.
vLocksteps works between VMs configured as an FT. This technology captures every input and output of the primary VM and sends it back to the secondary VM.
VLAN tagging helps to segregate the type of traffic coming towards a virtual machine from a standard switch.
There are three network security policies used in a standard switch.
I) Promiscuous mode – If you select Accept, VM will receive all the traffic port groups via vSwitch. The default mode is rejected.
II) MAC address change – If you select Accept, a host will accept requests to change the effective MAC address. The default mode is rejected.
III) Forged transmits – If you select Accept, a host will not compare the source and effective MAC address transmitted from a VM. The default mode is rejected.
The PSC stands for the platform service controller. PSC was introduced in ESXi version 6 onwards and provides below services:
I) Single Sign-On (SSO)
II) VMware Certificate Authority (CA)
III) Licensing services
IV) Reverse Proxy Services
There are two methods to deploy a PSC:
From ESXi 6.7, External PSC deployment is not supported per VMware.
There are two methods to deploy a vCenter Server:
I) Embedded Deployment
II) External deployment
From ESXi 7.0 onwards you can not use windows based machine to install a vCenter Server. It is the only appliance-based available now.
VMware Content Library is the central place to store and share files/images in vCenter Servers to multiple locations.
We have collected all these top VMware interview questions and answers with our experience and hope it will help you to clear the basic VMware interview. Although there are many advanced topics left in this section such as vSAN, NSX, vRealize OPS, VMware Cloud, and suite but do not worry we will come up with a new article on it soon.
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