How VM is started

Starting up a virtual machine (VM) is not an easy task, there are a lot of things going on hidden from the plain sight and studying it alone is a challenging task. The goal of this post is to simplify the process of learning how the oVirt hypervisor works. The concept of the oVirt is illustrated in the process of starting up the VM, which covers everything from top to the bottom.

Disclaimer: I am an engineer working close to the host part of the oVirt, therefore my knowledge of the engine is limited.

Architecture

Let me start with explaining the main parts oVirt hypervisor architecture. It will help a lot in understanding the overall process of the VM startup flow. Following is the simplified architecture, where I omit auxiliary components and support scripts. This will allow me to focus on the core concept without distractions.

The architecture comprises of three main components: 1) web UI and engine, 2) VDSM, 3) guest agent.

The web UI is where the user makes the first contact with the oVirt hypervisor. The web UI is the main command center of the engine and allows a user to control all aspects and states of Continue reading