VMWare Top Interview Questions with Answers

Q 1) Explain about your production environment? How many cluster’s, ESX, Data Centers, H/w etc ?

Q 2) How does VMotion works? What’s the port number used for it?

ANS–> TCP port 8000

Q 3) Prerequisites for VMotion?

Ans–> 1)ESX Servers must be configured with VMkernal ports enabled for vmotion and on the same network segment

2)ESX Servers must be managed by the same Virtual Center server

3)ESX Must have compatible CPUs

4)ESX Servers muct have consisten Networks and NEtwroks labels

5)The VMs must be stored on shared storage – iSCSI or FC SAN or NAS/NFS

6)The VMs can not use localcd/floppy or internal only vrtual switches on the ESX server

Check out http://www.vmware.com/pdf/vi3_35/esx_3/

r35u2/vi3_35_25_u2_admin_guide.pdf for more information

Q 4) How does HA works? Port number? How many host failure allowed and why?

ANS–> Maximum allowed host failures within a HA cluster is 4. What happens if 4 hosts have failed and a 5th one also fails. I have still enough free resources to start up the virtual machines on the remaining hosts. Will HA start these virtual machines from the 5th failed host on the remaining hosts?

ANS) That depends. If you have admission control enabled, if there are any resource constraints some VM’s may not restart. If you have admission control disabled, the VM’s will get restarted on any host left in the cluster. However, that doesn’t mean they will be functional. Make sure you have enough port groups configured on your vSwitch for your Virtual Machine port group to accommodate Host Firewalls. On ESX/ESXi hosts, VMware HA needs and automatically opens the following firewall ports.

Incoming port: TCP/UDP 8042-8045

Outgoing port: TCP/UDP 2050-2250

Q 5) What are active host / primary host in HA? Explain it?

ANS–> When you add a host to a VMware HA cluster, an agent is uploaded to the host and configured to communicate with other agents in the cluster. The first five hosts added to the cluster are designated as primary hosts, and all subsequent hosts are designated as secondary hosts. The primary hosts maintain and replicate all cluster state and are used to initiate failover actions. If a primary host is removed from the cluster, VMware HA promotes another host to primary status. Any host that joins the cluster must communicate with an existing primary host to complete its configuration (except when you are adding the first host to the cluster). At least one primary host must be functional for VMware HA to operate correctly. If all primary hosts are unavailable (not responding), no hosts can be successfully configured for VMware HA. One of the primary hosts is also designated as the active primary host and its responsibilities include: n Deciding where to restart virtual machines. n Keeping track of failed restart attempts. n Determining when it is appropriate to keep trying to restart a virtual machine. If the active primary host fails, another primary host replaces it.

Q 6) Prerequisites for HA ?

ANS First, for clusters enabled for VMware HA, all virtual machines and their configuration files must reside on shared storage (Fibre Channel SAN, iSCSI SAN, or SAN iSCI NAS), because you need to be able to power on the virtual machine on any host in the cluster.

Second, VMware HA monitors heartbeat between hosts on the console network for failure detection. So, to have reliable failure detection for HA clusters, the console network should have redundant network paths. That way, if a host’s first network connection fails, the second connection can broadcast heartbeats to other hosts. Last, if you want to use DRS with HA for load balancing, the hosts in your cluster must be part of a VMotion network. If the hosts are not in the VMotion network, however, DRS can still make initial placement recommendations.

Q 7) How do DRS works? Which technology used? What are the priority counts to migrate the VM’s?

Q 8) How does snap shot’s works?

Q 9) What are the files will be created while creating a VM and after powering on the VM?

Q 10) If the VMDK header file corrupt what will happen? How do you troubleshoot?

Q 11) Prerequisites VC, Update manager?

Q12) Have you ever patched the ESX host? What are the steps involved in that?

Q 13) Have you ever installed an ESX host? What are the pre and post conversion steps involved in that? What would be the portions listed? What would be the max size of it?

Q 14) I turned on Maintenance mode in an ESX host, all the VM’s has been migrated to another host, but only one VM failed to migrate? What are the possible reasons?

Q 15) How will you turn start / stop a VM through command prompt?

Q 16) I have upgraded a VM from 4 to 8 GB RAM; it’s getting failed at 90% of powering on? How do you troubleshoot?

Q 17) Storage team provided the new LUN ID to you? How will you configure the LUN in VC? What would be the block size (say for 500 GB volume size)?

Q 18) I want to add a new VLAN to the production network? What are the steps involved in that? And how do you enable it?

Q 19) Explain about VCB? What it the minimum priority (*) to consolidate a machine?

Q 20) How VDR works?

Q 21) What’s the difference between Top and ESXTOP command?

Q 22) How will you check the network bandwidth utilization in an ESXS host through command prompt?

Q 23) How will you generate a report for list of ESX, VM’s, RAM and CPU used in your Vsphere environment?

Q 24) What the difference between connecting the ESX host through VC and Vsphere? What are the services involved in that? What are the port numbers’s used?

Q 25) How does FT works? Prerequisites? Port used?

Q 26) Can I VMotion between 2 different data centers? Why?

Q 27) Can I deploy a VM by template in different data centers ?

Q 28) I want to increase the system partition size (windows 2003 server- Guest OS) of a VM? How will you do it without any interruption to the end user?

Q 29) Which port number used while 2 ESX transfer the data in between?

Q 30) Unable to connect to a VC through Vsphere client? What could be the reason? How do you troubleshoot?

Q 31) Have you ever upgraded the ESX 3.5 to 4.0? How did you do it?

Q 32) What are the Vsphere 4.0, VC 4.0, ESX 4.0, VM 7.0 special features?

Q 33) What is AAM? Where is it used? How do you start or stop through command prompt?

ANS) VMware-aam = HA.

VMware purchased the HA technology from Legato, who originally coined it as “Automated Availability Manager”.

Q 34) Have you ever called VMWare support? Etc

Q 35) Explain about Vsphere Licensing? License server?

Q 36) How will you change the service console IP?

Note: ESX 4.0 Update 2 introduces a new tool that simplifies the process of creating or restoring networking in the ESX service console. For more information, see Configuring or restoring networking from the ESX service console using console-setup (1022078). Changing settings from the physical or remote console connection Changing the IP for the Service Console must be done from the physical console or through a remote console session. If you make changes through a network connection such as SSH, network connectivity to the Service Console disconnects because the Service Console’s network interface changes.

1.Run this command to set the IP address:

[root@server root]# esxcfg-vswif -i -n vswif0

where is the IP address and is the subnet mask.

Note: In this example, vswif0 is the Service Console adapter that is the interface to which you are applying the IP address change.

2.Open the /etc/hosts file with a text editor and modify it so that it reflects the correct IP address and hostname.

3.To change the default gateway address and the hostname, edit the /etc/sysconfig/network file and change the GATEWAY and HOSTNAME parameters to the proper values.

4.For the changes to take place, restart the network service with the command: [root@server root]# service network restart

Note: If you are required to edit the hostname, then you must reboot the host.

Note: This command breaks any current network connections to the Service Console, but virtual machines continue to have network connection. If the ESX host is managed by VirtualCenter or vCenter Server, you may have to remove and re-add the host to the

inventory. For more information, see ESX not working properly in VirtualCenter after IP address change (1005633).

Note: Making changes to IP and DNS server settings can have a negative impact on the normal operation of ESX/ ESXi, particularly in HA clustered environments. For more information, see Identifying issues with and setting up name resolution on ESX/ESXi Server (1003735).

Note: If the changed IP does not persist across a reboot, try deleting and recreating the Service Console vswif management interface. For more information, see Recreating Service Console networking from the command line (1000266). Changing the hostname without rebooting To dynamically change the hostname, run the command:

[root@server root]# hostname newname

Note: This command creates a temporary hostname change. This change is lost when the system is rebooted. Changing the DNS server settings To change the DNS server settings, update the nameserver IPs and search domain in the /etc/resolv.conf file. Changing settings in VMware vSphere or Infrastructure Client

To change the hostname, domain, DNS servers, and default gateway in VMware vSphere or Infrastructure Client:

1.Highlight the ESX host and click the Configuration tab.

2.Click DNS and Routing.

3.Click Properties.

4.To change the hostname, domain, and DNS servers, click the DNS Configuration tab and enter the appropriate values.

Note: Disable VMware High Availability if you do not want virtual machines to failover during the hostname IP change.

5.To change the default gateway, click the Routing tab and enter the appropriate value.

6.Reboot the ESX host for the changes to take effect .

7.Reconnect the ESX host to vCenter Server with the new IP address. Generating new certificates for the ESX host The ESX host generates certificates the first time the system is started. Under certain circumstances, it might be required to force the host to generate new certificates. Typically new certificates only need to be generated if the hostname has been changed or the certificates have been deleted accidentally.

Each time you restart the vmware-hostd process, the mgmt-vmware script searches for existing certificate files ( rui.crt and rui.key). If the files cannot be found, new certificate files are generated.

To generate new certificates:

1.Put the host into Maintenance Mode.

2.In the directory /etc/vmware/ssl, back up any existing certificates by renaming them with these commands:

[root@server root]# mv /etc/vmware/ssl/rui.crt /etc/

vmware/ssl/orig.rui.crt

[root@server root]# mv /etc/vmware/ssl/rui.key /etc/

vmware/ssl/orig.rui.key

Note: If you are regenerating certificates because you accidentally deleted them, you do not have to rename them.

3.Reboot your host to allow it to begin using the new certificate, or restart the host services:

a.Restart hostd, using this command:

service mgmt-vmware restart

b.Restart vmkauthd, using this command:

service vmware-vmkauthd restart

4.Exit Maintenance Mode.

5.Confirm that the ESX host successfully generated new certificates by running this command and comparing the time stamps of the new certificate files with orig.rui.crt and

orig.rui.key:

[root@server root]# ls -la /etc/vmware/ssl/rui*

Notes:

•Disable VMware High Availability if you do not want virtual machines to failover during

the hostname IP change. If you are using vSphere 4.x you can just disable

host monitoring in the HA settings.

•For related information, see Verifying ESX Server host networking configuration on the service console (1003796).

•You may be required to regenerate your SSL certificate. For more information, see Replacing or Regenerating an SSL Certificate for the Management Interface (1843).

•You are required to edit files on an ESX host. For more information, see Editing files on an ESX host using vi or nano (1020302).

•For information on replacing VirtualCenter Server ceritificates, see:

Replacing VirtualCenter Server Certificates in Virtual Infrastructure 3

Replacing VirtualCenter Server Certificates in vSphere 4

•The iSCSI Qualified Name used for iSCSI storage configuration is based on the hostname of the ESX host. If you change the hostname of the ESX host, ensure to review your iSCSI software initiator configuration. For more information on iSCSI troubleshooting, see Configuring and troubleshooting basic software iSCSI setup (1008083).

•For more information on changing the hostname, see Changing the name of an ESX host (1010821).

Q 37) What’s the difference between ESX and ESXi?

Q 38) What’s the difference between ESX 3.5 and ESX 4.0?

Q 39) P2V Prt Number and Log file location?

TCP/IP Ports Required by VMware Converter Table lists the ports Converter uses in the conversion process. If your VirtualCenter Servers or ESX Servers are configured

to listen on port 905, you will have to make adjustments accordingly. Communication Paths | Port Converter application to remote physical machine | 445 and 139 Converter application to VirtualCenter Server | 902 Converter application to ESX Server 3.x | 902

Physical machine to VirtualCenter Server | 902

Physical machine to ESX Server 3.x | 902

Log File Locations:

UFAD logs:

%WINDIR%\Temp\vmware-temp\vmware-converter*

%WINDIR%\vmware-temp\vmware-converter* (in Windows

NT)

Client logs:

%TEMP%\vmware-temp\vmware-client*

Send these in to support using File > Export Logs. For Converter Boot CD, map a network drive using the network configuration tool (see Chapter 5, “Using the

Converter Boot CD for Local Cold Cloning,” on page 37) and use File > Export Logs.

Q 40) Micro vMotion

—————————————————————————————————

——————————————————————–

Q: How is VMware more stable than, say, a new physical server?

A: The idealized hardware provided by VMware provides a consistent virtual hardware

environment that increases that stability of your virtual machines independent of the underlying physical hardware.

Q: Is any installation method better than any other?

A: No. Whichever installation method you’re comfortable with and that produces a good build is the one for you.

Q: I’m having problems with my installation. What should I do?

A: Ensure that the hardware you’re loading ESX Server on is supported. The same goes for the configuration. If you are certain the hardware and configuration are supported, then run the vm-support script mentioned previously.

Q: Why does this chapter include only the graphical installer method?

A: It’s the recommended installation method from VMware and one that many in the x86-world are the most comfortable with. If you wish to try it another way, VMware offers a very complete installation document covering the various installation methodologies.

Q: When I copy my virtual machine and try to run it on my network, I get hostname already exists and IP address already exists errors. I thought I could simply copy my virtual machine. What is the problem?

A: You can copy your virtual machine, which is why you’re running into this problem. The copy is an exact copy. Thus, you need to change the hostname, IP address, and even the computer’s SID (if it has one).

Q: Can I move my Gold Master to my other ESX Servers?

A: Yes, it’s a recommended time-saver. If your ESX Servers share a LUN, that too is a way to access your Gold Master or your VMlibrary for that matter.

Q: Are there any limitations to the number of virtual machines I can run on my ESX Server?

A: Yes. Each ESX Server allows for only 80 virtual CPUs and 200 registered virtual machines.

Q: Can I take a virtual machine running on VMware Workstation or GSX and run it in ESX?

A: It depends. The process is not as simple as cutting and pasting. There is a specific import process required for migrating virtual machines from either Workstation or GSX

into ESX. Access the following link for the exact instructions: http://www.vmware.com/pdf/mobility_guide.pdf.

Q: Do you need to tweak the settings of your virtual machines after you’ve built them?

A: No. VMware has configured the defaults of your build to suit most server loads. However, depending on the profile of your server and the resource intensiveness of the service it’s providing, you may want to consider tweaking some of the default settings to better ensure service stability and reliability.

Q: Are there more advanced features than the ones detailed in this chapter?

A: Yes… a lot more.

Q: Is clustering more stable in VMware?

A: We find that the idealized hardware, in combination with VMware’s improvements in clustering support, has made virtual clustering very stable.

Q: Can you Vmotion a cluster?

A: That depends on the cluster type and how it is configured. Clusters using Raw Device Mapping in virtualmode can be moved with Vmotion according to VMware documentation.

Q: Does VMware support NIC teaming?

A: Yes, and it’s a very good idea to configure your ESX Server, especially if it’s for production, with teamed NICs. This will provide hardware fault tolerance in case one NIC fails.

Q: How many physical NICs do I need on my ESX Server?

A: That depends on the number of virtual machines and the network traffic they produce. You should have a minimum of two: one for your Service Console and one dedicated to your virtual machines.

Q: If I’m building a cluster using Microsoft Clustering Service, what’s the best configuration for my heartbeat NIC?

A:For a Cluster in a Box, create a VMnet that your nodes of your cluster can attach their heartbeat NICs.

Q: Can you attach virtual machines on any ESX Server to a VMnet?

A: No. Only virtual machines on the ESX Server that the VMnet resides can attach to it.

Q: Why should you pay for a p-to-v toll when there are a number of ways to do it for free?

A: If you don’t have the time or inclination to learn the manual process or need the assurance of a vendor for your physical-to-virtual migrations, then a tool that comes with support is a very reasonable option.

Q: What takes the longest in the p-to-v process?

A: Transferring the data of the physical server into either an image file or the virtual server itself. That’s why tweaking your network settings for optimal throughput is essential when p-to-v’ing a server.

Q: Can you create complete backups of your physical servers and then recover them into virtuals?

A: I’ve used NTBackup to back up Windows 2000 Professional and Windows XP, and created virtuals out of .bkf files. It works but there’s a bit of futzing around with the virtual once it is running. Try it.

Q: What’s the most essential part of creating a smooth migration plan?

A: Practice. No matter what the tool or process, practice it and learn its gotchas and the workarounds. No matter what method you use, there will be times when it won’t go as planned. Practicing your p-to-v process on a number of physical platforms and disk configurations allows you to become more adept once you’re doing it for real.

Q: Will my software vendor support my application in a VMware environment?

A: You’ll need to contact your specific software or applications vendor to find out; however, an increasing number of software vendors support virtualized environments. Once you’ve migrated your application from a physical to virtual environment it’s very easy to migrate back to a physical environment for vendor support. An excellent document provided by VMware can be found at the following link: www.vmware.com/pdf/

ms_support_statement.pdf.

Q: What are the best enablers to help ensure our server consolidation is a success?

A: Engaging with the lines of business and application owners not only assists in attaining an actionable schedule, but also develops a highly collaborative environment that facilitates buy-in and support for your project. In addition it will be difficult to incorporate rationalization into your project unless you are working directly with the business or application owners.

Q: What tools do you recommend for a server consolidation or virtualization project?

A: It’s imperative to have a robust and comprehensive tool for capacity planning, including historical data. This tool can be utilized in every phase of your project. Other tools to support the project include modeling tools used in test consolidation scenarios. Finally, you’ll need to evaluate and document tools and processes for each technology you wish to consolidate. The migration tools will need to support all the platforms you wish to use in your migration scenarios.

Q: What is the VMlibrary?

A: The VMlibrary (/vmlib) is simply a directory on your ESX Server that lets you organize the tools and files you need to manage and maintain your virtual infrastructure,

Q: Can ISOs be shared between ESX Servers?

A: If you place your VMlibrary on a LUN that’s shared amongst your ESX Servers, you can share your ISO images or anything else you place in your VMlibrary.

Q: Why is Vmotion so cool?

A: Try it…and then imagine the possibilities and applications. You’ll be a convert soon enough.

Q: You mentioned that additional ISVs were creating management capabilities for virtual infrastructures in their products. Which ones?

A: Look at HP Insight Manager, Dell OpenManage, IBM Director, BMC’s Patrol product line, Computer Associates’ Unicenter, and many others.

Q: I can’t add a new virtual hard drive to my virtual machine. What should I do?

A: You may not have the appropriate permissions to add virtual hardware to the VM, or the VM may be powered on and won’t allow the addition of virtual hardware while powered on.

Q: I just created a new virtual machine and attached to an existing disk. Every time I power on the VM, I get a blue screen. What could the problem be?

A: Make sure the OS type that you selected when you created the VM matches the OS type installed on the virtual disk. For example, if you selected Windows 2003 Standard for the VM when you created it, but the existing virtual disk has Windows 2000 Standard installed, you’ll probably encounter issues.

Q: I followed the directions for Active Directory authentication, and I still can’t log in using an account and password in AD. What should I do?

A: Check the time on your ESX Server and Active Directory and make sure they’re synced up. Kerberos is very sensitive to being out of sync and could reject credentials if the time is not within specific limits. You can also review the System event logs for clues.

Q: What is the most important aspect of deploying ESX Server and virtual machines?

A: The ability to provide service at least as good as that which you had with physical servers. With adherence to best practices, you should easily be able to provide this and exceed it by a phenomenal degree.

Q: ISOs have been mentioned in several of the chapters. Why are they so important?

A: Good administrators strive to never leave their chairs, cubes, or offices. If they do, they may just run into a user (we’re kidding, of course). Having a library of ISOs can help you in this endeavor. In addition, they run a lot faster than regular CDs.

Q: What will happen if I deploy systems management software on the ESX Server itself?

A: If you’re going to do this, make sure you allocate enough memory so that the application doesn’t impact the performance of your ESX Server and thus your virtual machines. Also, use a system management package that is supported and test your installation on your ESX Server thoroughly. If you notice a degradation of performance, contact the systems management software vendor. The major vendors have instructions and best practices for deploying their products onto ESX Server.

Q: What is the most important best practice to follow?

A: The one that ensures your smooth evolution into a virtual infrastructure education. Learn every aspect of a virtual environment to the best of your ability. Be passionate about it and you’ll reap the rewards. See the recommended reading list, troll the VMware Web site regularly, as well as other Web sites dedicated to virtualization such as p2v.net, vmguru.com, and virtual-strategy.com.

Q: Which version of VMware ESX Server supports Boot from SAN?

A: ESX Server 2.5 supports Boot from SAN but has the following limitations: ESX server had to be installed in boot from SAN mode, the HBA can only be used by the Service Console, LUN masking should be used to restrict other ESX servers from the boot LUN, the HBA of the boot LUN must be a QLogic HBA, and the boot LUN must be the lowest numbered LUN controlled by the storage processor.

Q: Where are log files for VMware ESX Server written to?

A: /var/logs/vmware

Q: What do you do if you forget the root password of the Service Console?

A: You will need to boot into single-user mode from the Service Console by selecting linux from the LILO boot menu and appending -s to your boot choice. This will boot the console into single-user mode and will allow you to use the passwd command to change the root user password.

Q: Why do I still see processes for my virtual machine when running the ps command on the Service Console even though my virtual machine is powered down?

A: If there is still a virtual console session running for your VM, you will still see processes associated with it for mouse, keyboard, and screen (MKS) even though it is powered off.

Q: I accidently unmounted the VMFS volume on my ESX Server. How can I re-mount the volume without re-booting

A: You can type mount t vmfs vmfs /vmfs

Q: What software is qualified for use with VMware 2.5.1?

A: Please see http://vmware.com/pdf/esx_backup_guide.pdf for an up-to-date list of software that’s compatible with ESX.

Q: What SANs are compatible with ESX Server?

A: Please see http://vmware.com/pdf/esx_SAN_guide.pdf for details on ESX-to-SAN server compatibility.

Q: What are the certified backup tools for ESX?

A: Please see http://vmware.com/support/esx25/doc/backup_tools_links.html.

Q: Can I back up my entire virtual machine from the Service Console?

A: Yes, but it is not advised. The console services should be left alone to manage the entire virtual machine infrastructure. It’s best that backups be performed by separating the applications and data from the operating systems because backups can become quite large very quickly. You should consider a backup of the environments that change frequently (data and applications) with an agent specifically designed to perform this function. A backup of those virtual disks that change infrequently and need VMFS formats should be backed up from the Service Console. These console-based backups should be performed in a powered-down or suspended approach (preferred), or a suspended environment using redo logs as an alternative. All backups performed from a systems console mode must be restored in an all-or-nothing approach. Recovery for a single file or directory can only be accomplished via a backup agent or from a backup to a SAN environment using a variety of different recovery/ restoral techniques.

Q: I’m not able to connect to the Service Console over the network. What could the issue be?

A: You may have allocated the Service Console NIC to the VMkernel. Use vmkpcidivyi to reassign the NIC to the Service Console.

Q: I have a virtual machine that did not start up correctly, but now I can’t power it down from the MUI or Virtual Center. How can I get this VM to shut down?

A: You can use the vmware-cmd utility to force a hard power down. The following syntax should work: vmware-cmd /path-to-vm/vm-directory/vm.vmx stop hard

Q: I find using commands to be very difficult. Why can’t I use X Windows on the Service Console?

A: You actually could run the X Windows system on the Service Console, but it will eat up valuable resources that are needed by the system to manage all the processes related to Virtualization. VMware specifically says not to run X Windows on the Service Console. So, it’s best to just buck up and deal with it.

Q: Is there a way to mount the vmfs volumes if they accidentally get unmounted without having to reboot?

A: Yes. You can run mountt vmfs vmfs /vmfs.

Q: How do I check the speed and duplex setting of the Service Console NIC? Also, how do I change it if needed?

A: You’ll need to cat out the eth0.info file for your type of adapter. This file can be found at /proc/net/type-of-nic/eth0.info. To give you an example, our server has an Intel Pro 100 Nic for the Service Console, so for us to find the speed and duplex information we would type: cat /proc/net/PRO_LAN_Adapters/eth0.info.

Q: How long has Xen been around?

A: Since 2004, and they’re located in Palo Alto, California. Hmm…what other virtualization company is in Palo Alto?

Q: What is a hypervisor?

A: In VMware parlance, it’s the virtualization layer.

Q: Why did VMware limit its beta of ESX Server 3.0 to so few?

A: Good question…We don’t know, and we hope that VMware’s future beta programs are opened up to a larger audience.

Q: If I can’t get a SAN, will local storage with a RAID device be sufficient?

A: Absolutely. You won’t get some of the cooler tools like VMotion, but being virtual on local storage is better than remaining physical.