What is the difference between VMware ESX, ESXi, vSphere and vCenter?

It is quite easy to confuse the VMware products ESX, ESXi, vSphere and vCenter. The purpose of this article is to demistify the whole thing. But first a little background. Virtualization technology allows multiple servers to be installed on the same physical machine. In just the last five years server hardware capability has increased so much that you can virtualize just about any server on the market today. This has enabled organizations to do a lot more with fewer resources.

For those new to VMware a brief explanation of VMware’s core offerings can help to minimize confusion. There are several layers/dimensions: the bare metal server, the hypervisor, the management server and the OS layer. VMware calls the whole thing vSphere but that is a bit confusing.

ESX and ESXi are the hypervisors that most commonly sit right one on bare metal. On “bare metal” means that is the first thing you install on the server before any OS. ESX is used for large scale custom implementations but for most of us ESXi is all you will need because it is easier to configure and more common for typical deployments. In the above picture the bare metal machine is the lowest level indicated by the gray box,  the ESX/ESXi layer is the blue section that says VMware.

ESXi has a tiny footprint when installed and takes up as little as a few hundred MBs on a drive when fully installed. I ran ESXi from a USB stick on a Dell R510 without issue. This is because it is basically just a liaison between the hardware and the OS layers. This is simplifying it for a quick explanation.

ESXi is a fairly uncomplicated to install and configure. Once it is installed and the IP address, subnet, gateway and hostname are configured it is ready to be managed with vSphere Client, the standard VMware management platform.

vSphere is the client application that you use to manage EXSi hosts, VMs and vCenter. It can be installed on any computer including workstations or servers, whether physical or virtual machines. However, if using vSphere to manage ESXi hosts directly without vCenter, you don’t get all the bells and whistles like HA and vMotion.


vCenter Server (installed on Windows) or vCenter Server Appliance (standalone) provide the rich feature set and management components to accomplish much more than the typical hypervisor. There is High Availability and virtualization automation capabilities that make your data center quite resilient.

A newer addition to the ecosystem is the Web Client Plug-in, which supports access to the new features in ESXi and vSphere 5.5 and 6.0. The Web Client is version 5.5 is not as user friendly as the vSphere Client but version 6.0 is big improvement.

If you have not already done so, find an old server, install VMware ESXi and get virtual!

How to Clone VM without vCenter

vmware logo

vCenter is really straightforward for tasks like cloning a server image. ESXi, however, is rather spartan when it comes to features. Many management tasks can still be performed with command line interface by using a tool like PuTTY.

You just got a new bare metal server and you want to setup VMware ESXi and vCenter but a prerequisite for installing vCenter is a configured domain. If you are working in an environment without a Domain Controller then you will have to configure a VM to be a DC on your VMware ESXi host and setup a domain before you can install vCenter. Once vCenter is installed most management tasks are quite easy to accomplish with vSphere.

My endpoint goals:

  • Virtualize a physical server
  • Install ESXi on bare metal host
  • Install vCenter to manage VMs

The author assumes you have installed VMware ESXi 5.x or 6.x hypervisor on your host server and configured the basic parameters like IP address, subnet, gateway and host name. Outline of steps to create a master VM image:

  1. Create a VM
  2. Install OS
  3. Install VMware tools
  4. Update OS with the latest updates
  5. Install any apps you want on the master image
  6. Configure any settings you prefer on all your servers
  7. Follow steps below to clone

Steps to clone VM using only the bare metal install of ESXi:

Take a snapshot of the server you would like to use as the master image

Take Snapshot

Enable SSH on the host. Select the host > go to Configuration tab > Security Profile > Properties

turn on SSH

Scroll down > select SSH > click Options

Start SSH - Options

Start the service, you can stop it later to minimize security risks.

Start SSH

Download PuTTY and open it to establish an SSH connection. Input the IP address of your host to connect. In my case the host IP is Enter the root username and password in PuTTY to login to the host.

Navigate to your master VM to verify it is the location you expect by running these commands in PuTTY:

cd /vmfs/volumes
ls -la
cd datastore1
ls -la

Find Source

Create a Directory called Clone to store clone images.

mkdir Clone

If your snapshotted source VM is “DC1” located on “datastore1” the following is the command to clone the VM called DC1. The “-000001” suffix on the VM name is to capture a snapshot version. If there was no snapshot you could just have “DC1.vmdk” at the end of the source path. Paste this entire command as one piece:

vmkfstools -i /vmfs/volumes/datastore1/DC1/DC1-000001.vmdk /vmfs/volumes/datastore1/Clone/VC1.vmdk -d thin


“Clone” is the folder where it will be stored and “VC1” is the name of the cloned virtual disk. “-d” is for the disk format, in this case thin provisioned. We will now create a new VM in vSphere and use the existing virtual disk.

Create a new VM in vSphere

create new VM

Select Typical

create new VM 2

Name the VM

create new VM 3

Select the target datastore

create new VM 4

Select the guest OS, in my case Server 2012 R2

create new VM 5

The default is 1 NIC, which is fine but I prefer to add a second internal NIC for VM to VM traffic that I previously setup

create new VM 6

Put whatever you want here because you will be deleting it anyway so you can add the cloned VD you already saved

create new VM 7

Select Edit the virtual machine before you continue

create new VM 8

In the Edit window, select the “New Hard Disk” you just entered parameters for and select Remove

create new VM 9

Select Add

create new VM 10

Select Hard Disk

create new VM 11

Select Use an existing virtual disk

create new VM 12

Browse to your Clone folder in the appropriate datastore, for me it was datastore1

create new VM 13

Next > Next > Finish

create new VM 14

Hooray, you have just created a cloned VM using command line!

create new VM 15

Hope this helps!