What is VMware ESXi and what operating systems does it support?

Virtual machines are often very useful for people who work with two operating systems. For example, if you do all your development on Linux, but still need Windows to play. In this case, running a Linux virtual machine on your computer saves you from buying a second computer.

However, most virtualization software runs on top of the existing “host” operating system. But if you want to cut out the middleman and have the virtualization software interface directly with the hardware, you should use a bare-metal hypervisor like VMware’s ESXi.

What is VMware ESXi?

VMware ESXi is VMware’s bare metal hypervisor, also known as type 1 hypervisor. It is basically a special operating system that runs directly on your system’s hardware and allows guest operating systems to interact directly with system components, hence its name: bare metal .

It differs from other virtualization software, such as Wine or VMware’s VirtualBox, which are type 2 hypervisors. In a type 1 hypervisor, the guest VM (virtual machine) and additionally the operating system running on said VM connect directly to the system hardware. In contrast, type 2 hypervisors run on top of the host operating system like regular applications and can then run virtual machines on top of the host operating system.

This means that a single VMware ESXi server can support multiple installations of the same or different operating systems, all running in isolated environments. This practice is called server consolidation and is often used in large enterprises where the savings in hardware, cooling and power costs can be significant.

In general, ESXi is one of the components offered in the vSphere software suite provided by VMware. Other products that typically work in tandem with ESXi include vCenter Server, VMware Directory Service, and vCenter Server Database, among others.

There are several key differences between these two types of hypervisors. However, Type 1 hypervisors are generally considered better because they offer better performance and are more secure because VMs are isolated in nature.

Vmware ESXi Features

Designed for enterprise applications, ESXi offers a number of features, including:

  • Small footprint: The entire package weighs only around 200 MB. This means that ESXi can be run on machines with fewer resources, and this is a security measure, as a smaller footprint means less attack surface mitigation.
  • Wide operating system support: ESXi servers support almost every operating system you can install on a regular machine. Windows, Linux, and macOS can all be installed using ISO files just like a regular VM.
  • Easy administrative access: Managing ESXi VMs is simple with an HTML-based web interface. After the installation is complete, you can log in to ESXi as a server. This means that VMs can be created, deleted and managed remotely.
  • Security: Beyond the security that a bare-metal hypervisor provides by default, VMware also protects your ESXi VMs using built-in encryption, role-based access, and pretty good logging and auditing capabilities.
  • Easily measurable: A single ESXi installation can use multiple CPUs simultaneously. It can also be configured to run up to 128 vCPUs and 120 VMs on up to 6TB of storage.
  • Customer Support and Compliance: Being a popular enterprise platform, you get extensive support and reseller opportunities. Its small footprint also allows for quick configuration and deployment of ESXi servers.

ESXi Requirements and Installation

As we mentioned earlier, ESXi hypervisors do not have a large footprint, meaning the minimum requirements are:

  • At least a dual-core host processor (64-bit, x86 processor). See the VMware ESXi system requirements for a complete list of supported processors.
  • At least 4 GB of RAM and 4 GB of storage.
  • One or more gigabit or faster Ethernet controllers.
  • Hardware virtualization support for 64-bit VMs (Intel VT-x or AMD RVI).

As you can imagine, you can turn almost any modern machine into an ESXi server as long as you meet the requirements mentioned above. As with VMware, there are additional requirements for more advanced things like storage redundancy. Booting to ESXi can be done using USB drives, hard drives, or CDs that use UEFI.

Installing ESXi is also quite simple. VMware provides an easy-to-use installation wizard similar to installing an operating system on your computer. Simply run the installation wizard using one of the bootable media mentioned above and follow the instructions. The video above shows how to install VMware ESXi.

Updating VMware ESXi Hosts

There are several ways to update your ESXi host. Updating a host is also fairly simple, although you should always install the latest version (version 7.0 at the time of this writing) if you’re installing a new ESXi host.


Overview of the ESXi upgrade process.
Image credit: VMware

You can upgrade your ESXi 6.5 or 6.7 hosts to version 7 using a CD, DVD, or USB key, depending on the host. A scripted upgrade, ESXCLI or vSphere Lifecycle Manager is also possible.

Installing and Updating VMware Tools on ESXi Hosts

If you want to get additional features from your VMs, you can also install or update the VMware Tools ISO on your VMs. This is usually done using VMware vSphere Update Manager (VUM) or VMware vSphere Lifecycle Manager (vLCM), but it can also be done manually.

However, a full installation of ESXi should install VMware Tools by default, so your only concern here is keeping the entire system up to date, which should happen automatically when you update your ESXi host.

Backup ESXi VMs from VMware

Data backup and backups are an extremely important part of IT business workflows. Depending on the type of backup you want to perform, you have the following options.

  • Backing up the VM hard drive: If you only want to back up the VM’s hard drive, you can choose to back up only the VMDK file associated with a specific VM in vCenter.
  • Backup entire VM: If you want to save yourself the trouble of setting up another VM and just want a ready-to-use copy, exporting your VM to an OVF template in vCenter is the quickest way. This way, configuration files, data, and installed programs are all moved into a single OVF file, which can be used to quickly deploy a VM to another ESXi host or even a VirtualBox installation.

Virtual machines can be useful

VMware’s ESXi hypervisor is surprisingly easy to install and use, even for those new to the world of virtual machines and IT infrastructure management.

Even if you don’t want to go down the rabbit hole of ESXi host and server software, VMware’s VirtualBox lets you run virtually any operating system on top of your existing system, opening up a whole new world of possibilities for you.

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