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Tuesday, October 9, 2012

Vmware Interview Questions - Part 1

1. VMWare Kernel is a Proprietary Kenral and is not based on any of the UNIX operating systems, it's a kernel developed by VMWare Company.

2. The VMKernel can't boot it by itself, so that it takes the help of the 3rd party operating system. In VMWare case the kernel is booted by RedHat Linux operating system which is known as service console.

3. The service console is developed based up on Redhat Linux Operating system, it is used to manage the VMKernel

4. To restart webaccess service on vmware
service vmware-webaccess restart – this will restart apache tomcat app

5. To restart ssh service on vmware
service sshd restart

6. To restart host agent(vmware-hostd) on vmware esx server
service mgmt-vmware restart
7. Path for the struts-config.xml

8. To start the scripted install the command is
esx ks=nfs:111.222.333.444:/data/KS.config ksdevice=eth0
location device name
9. Virtual Network in Simple……………….
Virtual Nic(s) on Virtual Machine(s) ----->

Physical Nic on the ESX Server (Virtual Switch - 56 Ports) ----->

Physical Switch Port Should be trunked with all the VLANS to which the VM's need access

All the ESX servers should be configured with Same number of Physical Nics (vSwitches) and Connectivity also should be same, So that vMotion succeeds
All the Virtual Machines are connected to one vSwitch with Different VLANS, this means the Physical Nic(vSwitch) needs to be trunked with the same VLANS on the Physical Switch Port

10 What are the three port groups present in ESX server networking
1. Virtual Machine Port Group - Used for Virtual Machine Network
2. Service Console Port Group - Used for Service Console Communications
3. VMKernel Port Group - Used for VMotion, iSCSI, NFS Communications

11. What is the use of a Port Group?
The port group segregates the type of communication.

12. What are the type of communications which requires an IP address for sure ?
Service Console and VMKernel (VMotion and iSCSI), these communications does not happen without an ip address (Whether it is a single or dedicated)

13. In the ESX Server licensing features VMotion License is showing as Not used, why?
Even though the license box is selected, it shows as "License Not Used" until, you enable the VMotion option for specific vSwitch

14. How the Virtual Machineort group communication works ?
All the vm's which are configured in VM Port Group are able to connect to the physical machines on the network. So this port group enables communication between vSwitch and Physical Switch to connect vm's to Physical Machine's

15. What is a VLAN ?
A VLAN is a logical configuration on the switch port to segment the IP Traffic. For this to happen, the port must be trunked with the correct VLAN ID.

16. Does the vSwitches support VLAN Tagging? Why?
Yes, The vSwitches support VLAN Tagging, otherwise if the virtual machines in an esx host are connected to different VLANS, we need to install a separate physical nic (vSwitch) for every VLAN. That is the reason vmware included the VLANtagging for vSwitches. So every vSwitch supports upto 1016 ports, and BTW they can support 1016 VLANS if needed, but an ESX server doesn’t support that many VM’s. :)

17. What is Promiscuous Mode on vSwitch ? What happens if it sets to Accept?
If the promiscuous mode set to Accept, all the communication is visible to all the virtual machines, in other words all the packets are sent to all the ports on vSwitch
If the promiscuous mode set to Reject, the packets are sent to inteded port, so that the intended virtual machine was able to see the communication.
18. What is MAC address Changes ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow incoming traffic to the VM. So by setting Reject Option both MAC addresses will be remains same, and the incoming traffic will be allowed to the VM.

19. What is Forged Transmits ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow outgoing traffic from the VM. So by setting Reject Option both MAC addresses will be remains same, and the outgoing traffic will be allowed from the VM.
20. What are the core services of VC ?
VM provisioning , Task Scheduling and Event Logging
21. Can we do vMotion between two datacenters ? If possible how it will be?
Yes we can do vMotion between two datacenters, but the mandatory requirement is the VM should be powered off.

22. What is VC agent? and what service it is corresponded to? What are the minimum req's for VC agent installation ?
VC agent is an agent installed on ESX server which enables communication between VC and ESX server.
The daemon associated with it is called vmware-hostd , and the service which corresponds to it is called as mgmt-vmware, in the event of VC agent failure just restart the service by typing the following command at the service console

" service mgmt-vmware restart "
VC agent installed on the ESX server when we add it to the VC, so at the time of installtion if you are getting an error like " VC Agent service failed to install ", check the /Opt size whether it is sufficient or not.

23. How can you edit VI Client Settings and VC Server Settings ?
Click Edit Menu on VC and Select Client Settings to change VI settings
Click Administration Menu on VC and Select VC Management Server Configuration to Change VC Settings

24. What are the files that make a Virtual Machine ?
.vmx - Virtual Machine Configuration File
.nvram - Virtual Machine BIOS
.vmdk - Virtual Machine Disk file
.vswp - Virtual Machine Swap File
.vmsd - Virtual MAchine Snapshot Database
.vmsn - Virtual Machine Snapshot file
.vmss - Virtual Machine Suspended State file
.vmware.log - Current Log File
.vmware-#.log - Old Log file

25. What are the devices that can be added while the virtual Machine running
In VI 3.5 we can add Hard Disk and NIC's while the machine running.
In vSphere 4.0 we can add Memory and Processor along with HDD and NIC's while the machine running
26. How to set the time delay for BIOS screen for a Virtual Machine?
Right Click on VM, select edit settings, choose options tab and select boot option, set the delay how much you want.

27. What is a template ?
We can convert a VM into Template, and it cannot be powered on once its changed to template. This is used to quick provisioning of VM's.

23. What to do to customize the windows virtual machine clone,?
copy the sysprep files to Virtual center directory on the server, so that the wizard will take the advantage of it.

24. What to do to customize the linux/unix virtual machine clone,?
VC itself includes the customization tools, as these operating systems are available as open source.

25. Does cloning from template happens between two datacenters ?
Yes.. it can, if the template in one datacenter, we can deploy the vm from that template in another datacenter without any problem.
26. What are the common issues with snapshots? What stops from taking a snapshot and how to fix it ?
If you configure the VM with Mapped LUN's, then the snapshot failed. If it is mapped as virtual then we can take a snapshot of it.
If you configure the VM with Mapped LUN's as physical, you need to remove it to take a snapshot.

27. What are the settings that are taken into to consideration when we initiate a snapshot ?
Virtual Machine Configuration (What hardware is attached to it)
State of the Virtual Machine Hard Disk file ( To revert back if needed)
State of the Virtual Machine Memory (if it is powered on)

28. What are the requirements for Converting a Physical machine to VM ?
An agent needs to be installed on the Physical machine
VI client needs to be installed with Converter Plug-in
A server to import/export virtual machines

29. What is VMWare consolidated backup ?
It is a backup framework, that supports 3rd party utilities to take backups of ESX servers and Virtual Machines. Its not a backup service.

30. To open the guided consolidation tool, what are the user requirements ?
The user must be member of administrator, The user should have "Logon as service" privileges - To give a user these privileges,open local sec policy, select Logon as service policy and add the user the user should have read access to AD to send queries

How VMWare Kernel different from other kernels?

VMWare kernel is a proprietary kernel that means that it is a registered kernel by VMWare Company and it is not based on any other kernel architecture or any other operating system. VMWare consists of a kernel that requires an operating system to boot it. A service console is being provided when VMWare kernel is booted.

What are the features provided by VMWare for easy access?

VMWare provides several features to make it easy for the user to access and maintain it. The features are as follows:
• VMWare provides web browser interface
• It provides easy to use wizard to configure the settings
• It provides tools to easily create hosts and maintain it from one place
• It provides easy maintenance of Virtual machines
• It provides easy graphics to configure the VMWare settings for security

What are the features of VMWare Player?

VMWare player is a stand-alone player that comes with the installation of VMWare also. The features that make it more popular are as follows:

• Creation of virtual machines can be done with easy install options. The creation and installation can be done directly to the system.
• VMWare Player can run any virtual machine and it can be used by anyone, anywhere. It allows quick and easy access, to take the advantage of security, portability and flexibility to manage the virtual machines.
• VMWare player allows sharing of virtual machines with other computers or users.

What are the different components used in VMWare infrastructure?

The different and major components used in VMWare infrastructure is as follows:
1. VMWare infrastructure consists of the lowest layer which acts as a ESX server host.
2. VMWare infrastructure also use the virtual centre server that keep tracks of all the VM related images and manage it from one point.
3. VMWare infrastructure (VI) client: this allows the client to interact with user's applications that are running on VMWare.
4. Web browser is used to access the virtual machines.
5. License server is used to create a server that provides licensing to the applications
6. Database servers are used to maintain a database.

What are the benefits of virtualization?

Virtualization is a creation of virtual machines and to manage them from one place. It allows the resources to be shared with large number of network resources. Virtualization is having lots of benefits and they are as follows:
1. It helps in saving lots of cost and allows to easily maintaining it, in less cost.
2. It allows multiple operating systems on one virtualization platform.
3. It removes the dependency of heavy hardware to run the application.
4. It provides consolidating servers that are used for crashing of a server purpose
5. It reduces the amount of space being taken by data centres and company data.

What is the purpose of a Hypervisor?

Hypervisor is a program that manages the virtual machine. It also act like virtual machine manager that manages the many virtual machines from one place. It allows multiple operating system to share single hardware host. Each operating system in this consists of its own defined space consisting of space, memory and processor. It is used as a controller program to control host processors and resources. It separates out the layer between many operating systems so that one can't conflict with another one.

How ESX server related to VMWare?

ESX server is the enterprise edition of VMWare. It provides server virtualization platform that allows many operating systems to be shared together in a convenient way and consists of a centralized management platform that is also known as virtual centre. ESX server is a virtualization technique that is used to create cloud applications and allows easy development of cloud platforms. It is related to VMWare as it is the upper layer of it.

What is the difference between ESX and GSX server?

GSX server acts as type 2 hypervisor that gets installed on the host operating system’s hardware like windows and Linux. VMWare workstation gets mixed up with GSX server to provide it more functionality to run your applications and operating systems. ESX server on the other hand, is type 1 hypervisor that runs its software directly on the system’s hardware and it doesn’t require any operating system prior to its installation. It is level 0 hypervisor and it has its own operating system.

What is the use of VMWare workstation?

VMWare workstation is software that allows user to run more than one operating system in there system. It provides virtualization to run different applications on many operating systems at a single time. It saves the current configuration of operating system for the user in the form of virtual machines. VMWare allows user to view there application and work with so many different OS without even switching between the OSs.

What are the different types of extensions used by VMWare?

1. .log: is used to keep a log file to maintain a key for VMWare. This file allows user to see the problems encountered during any installation or while using VMWare.
2. .nvram: is used to store the state of the virtual machine in system’s BIOS.
3. .vmdk: is a virtual disk file that is used to store the content of virtual machine.
4. .vmsd: stores the information and metadata of the system’s snapshots.
5. .vmsn: is used to store the snapshot state. It stores both the running state and the time when you have taken it.
6. .vmss: stores the suspended state of a virtual machine.
7. .vmtm: stores the configuration team data.
8. .vmx: store the primary configurations for the new virtual machine.

How virtual machine’s concept is different for host and guest systems?

Host system is the system that runs the operating system and over which the virtual platform can be installed. The virtual platform that runs another operating system is called as guest operating system. Host and guest can be connected with each other by using the virtual machines. A host system that runs all together its own operating system is called as virtualization host and the guest operating system will be that, which get installed over that operating system.

What are some major differences between VMWare Server and ESX server?

• ESX server is a bare metter virtualation platform that is a physical server whereas, VMWare server needs an operating system to run itself.
• ESX server is type 1 hypervisor virtualization platform whereas, VMWare server is a type-2 hypervisor virtualization platform.
• ESX server gives better performance then VMWare server, due to less overhead.
• ESX server have more features available then VMWare server.
• VMWare server is good to be used on small platforms and with less resources but, ESX server requires high specifications.

What is the use of Para-virtualization?

Para-virtualization is a virtualization technique that allows similar virtual machines to be created on particular hardware. It allows many operating systems to run on host hardware at the same time. It makes good use of resources like processors, memory and networking. It acts as a virtual machine monitor that has high performance and more efficient. It is used for development, testing and production of the virtual machines. It also good in disaster recovery by moving the guest virtual machine till the hardware is being repaired.

Why snapshots are really important in VMWare?

Snapshots are images that is been taken at a particular point from the virtual guest operating system. The snapshot consists of the virtual machine configurations, memory and the devices that were present at the time of the snapshot. By doing this, you can return back to virtual machine which might have become corrupted or might not be working. Snapshots can be taken anytime according to your need and requirement. Snapshots can be saved and then system can be reverted back in case of any disaster happened to your operating system.

What are the disadvantages associated with VMWare virtualization platform?

The disadvantage of VMWare virtualization platform is as follows:
• VMWare concept requires the knowledge of the concept.
• It requires money to buy the resources required for virtualization platform.
• It requires high end server with lots of high end configuration and specification that increases the cost.
• It requires different technologies that have to be implemented for the enterprise virtualization systems.
• Reliability decreases and cost increases in case of the system failures.

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