VM failing to powered ON | Module ‘Monitorloop’ power on failed | Current swap file size is 0 KB | Failed to extend swap file

 When you are powering on the VM and getting below error what do you need to do?

Error code

Module ‘Monitorloop’ power on failed

Failed to extend the virtual machine swap file

Current swap file size is 0 KB

Failed to extend swap file /vmfs/volumes/******

Login to ESXI host where you are getting above error 

Run below command to check list of VM VMs on the ESXi host

vim-cmd vmsvc/getallvms

Now you need to go to the failed VM director using cd command.


Note: - SHARED-DATASTORE01 ->Datastore name where failed VM is residing 

              DEMOPRDSRM01 -> Failed VM name

Now use “ls” to list out files

Now use ->   vi vmware.log (To read vmware.log file)

Now search for the error when it was failing to power on and you'll see something similar like whatever you were seeing in vCenter but in the easiest way. Like below


Now you need to check the free space on Datastore where your VM is running.

To check the free space on Datastore run the below command

vmkfstools -Ph /vmfs/volumes/SHARED-DATASTORE01   (P in caps and Datastore name)

Now only 719 MB free space available on Datastore, at least 1 GB free space is required to power ON the VM

Now run below command to check which file is taking more space.

Go inside the Datastore and run 

du -h command

Now you need to decide if you can delete any of the VMs from the Datastore to free up the space

If you want to delete any VM from the Datastore run below command.

/vmfs/volumes/61892dcd-b0d3dd11-0852-000c29b75dac] rm -rf /vmfs/volumes/SHARED-DATASTORE01/DEMOPRDSRM01

 Next time when you shall power on the VM it will power on.

Note-: You can manage Datastore space from the web console as well to free up the space.


How to fix if ESXi host is showing Not responding in vCenter | Reset management agent using DCUI | vpxa service restart in ESXi host

 How to fix if ESXi host is showing Not responding in vCenter

Below steps you need to check

Scenario 1 -> if the host is reachable and there is no lockdown mode enabled at host level.

  1. Ping the host


Pinging with 32 bytes of data:

Reply from bytes=32 time<1ms TTL=64

Reply from bytes=32 time<1ms TTL=64

  1. Login to host using web client -> If everything is fine start SSH service.

Login to ESXi host using putty console

Check VPXA service using below command

etc/init.d/vpxa status

Start the service using below command

etc/init.d/vpxa start

Now go to vCenter and check the status, it will take 2-3 minutes to sync.

  1. Scenario -> In case lockdown mode is enabled on ESXI host level 

As the lockdown mode is enabled on ESXi host level so you can’t connect using Webclient directly.

Login to iLO console -> Take remote console

Press F2 to login to host using DCUI with root credential

Go to troubleshooting options

Restart management agent

Press F (11) to restart management agent

Now management agent is restarting

Now go to vCenter and wait for 3-4 minutes to sync

VMware Command to check vpxa, hostd service status | start stop the vpxa & hostd service | 503 Service Unavailable (Failed to connect to endpoint

 Command to check vpxa, hostd service status | start stop the vpxa & hostd service

Login to ESXi host using putty session

Go to /etc/init.d/ and enter the service name and action type i.e status, start or stop

-> To terminate the service

[root@DEMOESX01:~] /etc/init.d/vpxa stop   

watchdog-vpxa: Terminating watchdog process with PID 526649

vpxa stopped.

-> To check the status

[root@DEMOESX01:~] /etc/init.d/vpxa status  

vpxa is not running

-> To start the service

 [root@DEMOESX01:~] /etc/init.d/vpxa start  

vpxa started.

If you are getting below error while accessing ESXI host

503 Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http16LocalServiceSpecE:0x00000000b6b48c80] _serverNamespace = / action = Allow _port = 8309)

Login to putty session

Check host d service status using below command

etc/init.d/hostd status

Start the host d service using below command

etc/init.d/hostd start

Now check ESXi host web console

Top 10 VMware interview questions and answers for Administrator level

 12. Which two traffic types can be configured for a dedicated VMKernel adapter?

 (Choose two)

Options are:  

  1. Discovery Traffic

  2. vMotion Traffic

  3. vSphere Replication Traffic

  4. vSphere Custom traffic

Ans is:

B. vSphere Replication Traffic

C. vMotion Traffic

Reason is: VMKernel  Adapters are specialized virtual adapters used for VMKernel

Services and also used by the vSphere host to communicate with the outside world.

  1. vMotion Traffic: vMotion is one of the most widely used VMKernel services in Datacenter operations. To perform vMotion, VMkernel adapter needs to be configured with vMotion service else vMotion check itself will fail.

  2. vSphere Replication Traffic: vSphere Replication is another widely used VMkernel service. To isolate the incoming replication traffic on target ESXI hosts, VMkernel adapter needs to be configured with vSphere replication service else management network will be used for replication traffic.

13. Where is a virtual SAN fault Domain configured?

 Options are:

  1. VMware virtual SAN cluster configuration

  2. VMware HA cluster configuration

  3. VMware DRS cluster configuration

  4. Datacenter advanced setting configuration

Ans is: 

A VMware virtual SAN cluster configuration

Reason is:  Fault Domain enables us to protect against rack or chassis failures without requiring 

Additional data copies. The implementation allows vSAN to save replica copies of virtual machine

Data in different domains. For ex. Different racks of compute.

14. During vCenter server upgrade, an ESXI 6.x host in a HA cluster fails. Which statement is true?

Options are:

  1. HA will fail the virtual machine over to an available host during vCenter server upgrade

  2. HA is unavailable during the vcenter server upgrade process.

  3. HA will fail the virtual machines over to an available host after the vcenter server upgrade process

  4. HA will successfully vMotion the virtual machine during the host failure.

Ans is:  C. HA will fail the virtual machines over to an available host after the vcenter server upgrade process.

vSphere HA will continue to restart protected VMs on available hosts in a cluster in the event of ESXi host failure. Any new ported on VM won’t be protected by HA until vCenter server is back online.

During vcenter upgrade process, HA admission control policies also can’t be changed or modified.

15. Which two statements are true regarding iSCSI adapters? (Choose two)

Options are:

  1. Software iSCSI HBA required VMkernel networking

  2. Independent HW iSCSI HBA offload processing from the ESXI host

  3. Dependent HW iSCSI HBA do not require vmkernel networking.

  4. Independent HW iSCSI HBA requires vmkernel networking.

           Ans is: 

  1. Software HA will fail the virtual machines over to an available host after the vcenter server upgrade process

  2. Independent HW iSCSI HBA offload processing from the ESXI host

Reason is: 

HBA : A host bus adapter (HBA) is an HW or software adapter that connects the host to storage devices.

iSCSI:  iSCSI stands for internet small computer systems interface. It is transport layer protocol enables host computer to send data to an eternal iSCSI- based storage array

16. Which features of VMware vSphere will automate the process of migrating VMs to fewer hosts during times of low workloads?

Options are: 

  1. FT

  2. EVC

  3. DPM

  4. HA

Ans is: C. DPM

Reason is:  DPM stands for Distributed power management. It provides additional power saving by dynamically consolidating workloads during periods of low resource utilization.

Virtual machines are migrated onto fewer hosts and then unneeded ESXI hosts are powered off.

17. An administrator is troubleshooting network communications between a vCenter server and an ESXi 6.5 host.

Which log shows the related events between these components?

Options are:

  1. /var/log/fdm.log

  2. /var/log/vpxa.log

  3. /var/log/hostd.log

  4. /var/log/auth.log

Ans is: B. /var/log/vpxa.log

Reason is: 

VPXD: vpxd is vcenter server service. If this service is stopped, then we will not be able to connect to VC.

VPXA: vpxa is the agent of VC which is installed on each ESXi host managed by VC.

HOSTD: hostd is another agent that runs on each ESXi host. It performs host specific operations like VM power on/off.

18. An administrator sees the following error in the log files:

Lost Access to volume ” Volume name **** due to connectivity issues” 

Which two events could be the source of the error message?

Choose two

Options are:

  1. vCenter server failure

  2. VXLAN failure

  3. Disk array failure

  4. ESXI failure

  5. Network failure

Ans is: 

Network failure (APD All path down)

Disk array failure   (PDL  Permanent device loss)

Reason is: APD (All paths down) situation occurs when all the paths to a device are down. Since there no indication whether device is permanent or temporary loss, ESXi keeps reattempting to establish connectivity. 

APD commonly occurs due to underlying storage/network connectivity issues and hosts still believe the device is available.

PDL (Permanent Device loss): situation occurs when the storage device is permanently inaccessible to ESXi host and ESXi host no longer attempts to re-establish connectivity issue.

In PDL state, iSCSI sense code logged by storage device to ESXi host used to recognize device inaccessibility. 

19. A vSphere administrator wants to reserve 0.5 Gbps for virtual machines traffic on each uplink of a distributed switch that has 10 uplinks.

What is the quota that should be reserved for the network resource pool?

Options are:

  1. 10 Gbps

  2. 5 Gbps

  3. 100 Gbps

  4. 0.5 Gbps

Ans is

B. 5 Gbps 

Reason is:

What is a network resource Pool?  A Network resource pool provides a reservation quota to virtual machines. The quota represents a portion of bandwidth that is reserved for virtual machine system traffic on the physical adapter connected to vDS.

You can set the bandwidth for the virtual machines from the quotas that are associated with the pool.

If the virtual machine system traffic has 0.5 Gbps bandwidth reserved on each 10 GbE uplink on a distributed switch which has 10 uplinks, then the total aggregated bandwidth available for VM reservation on this switch would be


Network resource pool can reserve a quota of 5 Gbps capacity.

Top 10 VMware scenario based interview questions and answers

1 .Which Information can the administrator use to identify ISCSI nodes?

Options are:

A.              MAC address

B.              IQN

C.              WWN

D.              LUN ID

Ans: B. IQN 

Reason is: IQN is an abbreviation for iSCSI qualified Name. IQN is used to identify iSCSI nodes in SAN networks, same as MAC addresses used to identify network devices in Ethernet networks.

Similar to IQN, WWN is used to identify FC/FCoE devices in SAN networks.


2.  An Administrator needs to prevent 2 virtual machines from running on the same host. Which DRS policy should be applied?


Options are: 

A.              VM-to-VM affinity

B.              VM-to-host affinity

C.              VM-to-VM anti-affinity 

D.              VM-to-host anti-affinity


Ans: VM-to-VM anti-affinity 

  1. Reason is: DRS Anti Affinity rules are used to prevent VMs running on the same host whereas Affinity rules are used to keep VMs together on the same host at any time. VM-to-host affinity rules are used to bind VM to specific hosts where VM-to-VM rules are about 2 VMs binding.  


3. An Administrator is planning a new vsphere deployment using shared storage. The solution must be supported.




RDM Disks


Options are:

A.              CIFS

B.              iSCSI

C.              NFS

D.              vSAN


Ans:  B. iSCSI

Reason is: iSCSI, NFS and vSAN, all three storage supports vMotion and storage vMotion feature. But only iSCSI is the block level storage which supports RDM disks. CIFS is file sharing protocols used for windows operating systems.

CIFS and NFS are file sharing protocols and vSAN is object based storage.


4. Which vSphere 6.X feature automatically distributes resources among the virtual machines during contention?


Options are:

A.              Storage vMotion

B.              vSphere vMotion

C.              DPM

D.              DRS


Ans :   DRS 

Reason is:  DRS stands for Distributed Resource Scheduler. DRS is a vSphere cluster level feature which provides resource management capabilities like Load balancing and virtual machine placement. DRS always strives to keep your VMs happy and allocate required compute resources to run VMs efficiently.


Storage vMotion -: Use to change underline Datastore of a VM.

vSphere vMotion-: Use to change underline host of a VM

DPM-: DPM is used for better power management of a VM.


5. Which vSphere 6.X feature enables you to mitigate the effect of storage latency during peak load periods in a virtualized data center?

Options are:

A.              NFS

B.              iSCSI

C.              NIOS

D.              SIOC



              Reason is: SIOC stands for Storage IO control

              The purpose of SIOC is to address the “Noisy Neighbor” problem where low priority VM impact high priority VMs. SIOC provides I/O prioritization of virtual machines running on shared storage. SIOC automatically throttles a virtual machine I/O bandwidth when latency threshold is exceeded.


6. What are two features of vSphere 6.x that help address the availability challenges any organization faces?

Options are:

A.              Host profiles

B.              VM templates

C.              High availability

D.              Fault tolerance

Ans is: High Availability

Fault tolerance

Reason is: High Availability or HA is one of the widely used vSphere cluster features to improve application availability. In the event of host failure, HA automatically detects the failure and evacuates VMs from the failure host and restarts it back on the available node of the cluster. By default, vSphere HA failure detection time is 15 sec.

vSphere Fault Tolerance or FT is another vSphere cluster feature which provides continuous availability to virtual machines –eliminating downtime and disruption- even in the event of a complete host failure. FT creates an exact replica of virtual machine to another host that can take over at the time of failure. FT provides ZERO DOWNTIME.


7. Which VLAN configuration requires physical switch connectivity to be defined as an access port?

Options are:

A.              Private vLAN

B.              External switch tagging

C.              Virtual switch tagging

D.              Virtual guest tagging


Ans is: External Switch tagging


Reason is: In external switch tagging, vLAN tagging happens at physical switch level, because of which switch ports are configured as access ports. Whereas in VST and VGT, physical switch ports need to be configured as Trunk ports because packets are tagged at virtual switch level or guest OS level.


8. Which two network failure detection options are available when using a vsphere standard switch?


Options are:

A.              Fixed with preferred path

B.              Link status only

C.              Beacon probing

D.              Most recently used.

Ans are: 

B. Link status only

C. Beacon probing

Reason why:  Link status only algorithm can detect immediate link failure for ex. NIC Down, Switch port Disable/Block, Switch Reboot etc.

Beacon probing Algorithm can detect upstream link and switch failures as well. It sends and listens for beacon probe packets in all physical NICs in a team.


9. An Administrator is migrating a powered on virtual machine. Which option should be selected to perform storage vMotion of the VM?


Options are:

A.              Change storage only

B.              Change Compute resource only

C.              Change both compute resource and storage

D.              All of the above

Ans is: Change storage only

Reason is: Storage vMotion is used to migrate virtual machine disk files from one Datastore to another with NO downtime for VM or No service disruption for end users.

SvMotion is used for storage maintenance activity or redistributing virtual machine disks to different storage volumes to balance capacity or improve performance.

10. Why would a vSphere administrator configure resource “SHARES” for a virtual machine?

Options are: 

A.              To prioritize access to a resource during contention 

B.              To guarantee access to a resource during contention

C.              To prioritize access to a resource at all times

D.              To guarantee access to a resource at all times

Ans is: 

A.              To prioritize access to a resource during contention 

Reason is: Shares specify the relative priority of a virtual machine. If a virtual machine has twice as many shares of resource as another vm. It is entitled to consume twice as much of that resource.

Shares prioritize cluster resource allocation only when available capacity is not able to meet the demands of resource consumers.


11. What two files are created when the TAKE SNAPSHOT operation is executed?

Options are:

A.              *.delta.vmdk

B.              *.nvram

C.              *.vmss

D.              *.vmsn


Ans are: 





Reason is:  A VMware Snapshot is a copy of the virtual machine’s disk file and memory state at any given point of time.



File represents the difference between the current state of the virtual disk and the state that existed at the time that the previous snapshot was taken.

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