What Is Meant By “Guest Machine” and “Host Machine”?

Imagine that you are hired to help migrate 20 servers to a Microsoft Azure cloud tenet. The servers are all VMware virtual machines running on two separate 4-host clusters and are accessible via the local vSphere 6.7 install.

At the initial team meeting, everyone introduces themselves to the group. Primary assignments are distributed afterward. Your primary assignment is to compile a list of all the guests and hosts in that instance of vSphere.

Additionally, you are to compile the following information for all the guest machines (per guest):

vCPU count
Memory size
Hard Disk 1 size (primary boot drive)
Whether the most recent VMWare Tools are installed on it

You instinctively know this is nothing more than a table. You can research this data and put together a simple Excel spreadsheet with this information … you only have one problem:

WHAT IS A GUEST MACHINE?

You pull a colleague to the side at the breakfast counter before the next workday and ask them this question. You also explain you are new to VMware and are learning the terminology.

They respond with, “It can get confusing, I know. Just remember: the guests run on hosts.”

They then run … cold vegetarian omelets are not a great way to start the day, as you know from your college dorm years.

OK, WHAT IS A HOST MACHINE?

Think of it this way. Let’s imagine you have a friend over to visit your home. You are the host, and they are the guest.

The host owns most of the stuff inside the home and also the house itself (assume homeownership). The guest can gain access to many things in the host’s home, but at that moment, the guest and what they can do is limited in some way to what the host has to offer.

This is similar to guest and host machines. The host has all the resources, and the guest is utilizing the host’s resources as much as possible and as needed. In this sense, the host is the hardware, and the guest is the combined operating system and applications.

So, in short, a guest is the operating system and the things that run on it, and the host is the computer hardware and parts that the operating system is running on.

Another way to think of this is to say, “the operating system and applications (guest) are hosted on the hardware.”

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