science

VMware ESX

VMware ESX is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand VMware ESX rather than just read about it. In short: VMware ESX (formerly named ESXi) and a different historic VMware ESX are enterprise-class, type-1 hypervisors developed by VMware, now a subsidiary of Broadcom, for deploying and serving virtual computers. As type-1 hypervisors, ESX is not a software application that is installed on an operating system (OS); instead, they include and integrate vital OS components, such as a kernel.

Key takeaways

VMware ESX belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect VMware ESX to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of VMware ESX from memory before moving on to harder problems.

Reference excerpt

VMware ESX (formerly named ESXi) and a different historic VMware ESX are enterprise-class, type-1 hypervisors developed by VMware, now a subsidiary of Broadcom, for deploying and serving virtual computers. As type-1 hypervisors, ESX is not a software application that is installed on an operating system (OS); instead, they include and integrate vital OS components, such as a kernel. Prior to ESXi 3.0 (released in 2008) there was only the original hypervisor named ESX, and for a while both hypervisor products existed (until the final 4.1 release of the historic ESX in 2010). ESXi replaces the Service Console (a rudimentary operating system) with a more closely integrated OS. ESX/ESXi is the primary component in the VMware Infrastructure software suite. However from version 9.0, VMware renamed ESXi to ESX despite the name having already been used before for their earlier hypervisor product. The name ESX originated as an abbreviation of Elastic Sky X. In September 2004, the replacement for ESX was internally called VMvisor, but later changed to ESXi (as the "i" in ESXi stood for "integrated").

Architecture ESX runs on bare metal (without running an operating system) unlike other VMware products. It includes its own kernel. In the historic VMware ESX, a Linux kernel was started first and then used to load a variety of specialized virtualization components, including ESX, which is otherwise known as the vmkernel component. The Linux kernel was the primary virtual machine; it was invoked by the service console. At normal run-time, the vmkernel was running on the bare computer, and the Linux-based service console ran as the first virtual machine. VMware dropped development of historic ESX at version 4.1, and now exclusively uses ESXi (since renamed to ESX in 2025), which does not include a Linux kernel at all. The vmkernel is a microkernel with three interfaces: hardware, guest systems, and the service console (Console OS).

Interface to hardware The vmkernel handles CPU and memory directly, using scan-before-execution (SBE) to handle special or privileged CPU instructions and the SRAT (system resource allocation table) to track allocated memory. Access to other hardware (such as network or storage devices) takes place using modules. At least some of the modules derive from modules used in the Linux kernel. To access these modules, an additional module called vmklinux implements the Linux module interface. According to the README file, "This module contains the Linux emulation layer used by the vmkernel." The vmkernel uses the device drivers:

net/e100 net/e1000 net/e1000e net/bnx2 net/tg3 net/forcedeth net/pcnet32 block/cciss scsi/adp94xx scsi/aic7xxx scsi/aic79xx scsi/ips scsi/lpfcdd-v732 scsi/megaraid2 scsi/mptscsi_2xx scsi/qla2200-v7.07 scsi/megaraid_sas scsi/qla4010 scsi/qla4022 scsi/vmkiscsi scsi/aacraid_esx30 scsi/lpfcdd-v7xx scsi/qla2200-v7xx These drivers mostly equate to those described in VMware's hardware compatibility list. All these modules fall under the GPL. Programmers have adapted them to run with the vmkernel: VMware Inc. has changed the module-loading and some other minor things.

Service console In the historic ESX, the Service Console is a vestigial general purpose operating system most significantly used as bootstrap for the VMware kernel, vmkernel, and secondarily used as a management interface. Both of these Console Operating System functions were deprecated since historic ESX development stopped at version 4.1 and so the next version of 5.0 was ESXi only. The Service Console, for all intents and purposes, is the operating system used to interact with VMware ESX and the virtual machines that run on the server.

Purple Screen of Death

In the event of a hardware error, the vmkernel can catch a Machine Check Exception. This results in an error message displayed on a purple diagnostic screen. This is colloquially known as a purple diagnostic screen, or purple screen of death (PSoD, named by analogy to the blue screen of death (BSoD)). Upon displaying a purple diagnostic screen, the vmkernel writes debug information to the core dump partition. This information, together with the error codes displayed on the purple diagnostic screen can be used by VMware support to determine the cause of the problem.

Versions VMware ESX used to be available in two main types: ESX (version 4.1 and earlier) and ESXi (version 3.5 onwards), but as of version 5, the original ESX has been discontinued in favor of ESXi (since renamed to ESX from version 9.0 onwards). Historic ESX and ESXi before version 5.0 do not support Windows 8/Windows 2012. These Microsoft operating systems can only run on ESXi 5.x or later. VMware ESX (formerly ESXi) is a smaller-footprint version of ESX which does not include the ESX Service Console nor use a Linux Kernel. Before Broadcom acquired VMware, it was available - without the need to purchase a vCenter license - as a free download from VMware, with some features disabled. ESXi stood for "ESX integrated". VMware ESX (formerly ESXi) originated as a compact version of VMware ESX (historic) that allowed for a smaller 32 MB disk footprint on the host. With a simple configuration console for mostly network configuration and remote based VMware Infrastructure Client Interface, this allows for more resources to be dedicated to the guest environments. Two variations of ESX exist:

VMware ESX Installable VMware ESX Embedded Edition The same media can be used to install either of these variations depending on the size of the target media. One can upgrade ESXi to VMware Infrastructure 3 or to VMware vSphere 4.0 ESXi. ESXi was originally named VMware ESX Server ESXi edition, through several revisions the ESXi product finally became VMware ESXi 3. New editions then followed: ESXi 3.5 up to ESXi 8, before being renamed to ESX with version 9.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with VMware ESX

Start with the simplest possible case. Write down what VMware ESX claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to VMware ESX before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about VMware ESX ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of VMware ESX

In research: VMware ESX appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses VMware ESX in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: VMware ESX is common in secondary-school and first-year university syllabi. It links to neighbouring topics VMware, so understanding it makes those chapters shorter.
In everyday life: Look for VMware ESX outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study VMware ESX in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what VMware ESX means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain VMware ESX out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is VMware ESX in simple terms?

Why does VMware ESX matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study VMware ESX?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on VMware ESX.