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Schoolyear AVD

Introduction

This chapter explains how to build the images that are used to boot the virtual machines to which students get access during their exam. This guide assumes you are familiar with building images for Windows machines.

In theory, you could use any Windows image in Schoolyear AVD, however, to keep the user-experience optimal for students we strongly recommend sticking to the Exam-Ready image guidelines set forth in this chapter.

To simplify the process of building Exam-Ready images, we’ve published the avdcli commandline tool.

Exam-Ready images

Exam-Ready images are VM images that are optimized for use in examination setups. The virtual machines used for examination are short-lived and mostly isolated from any network. Common packaging tools rely on on-demand download of installation packages and caching. These tools work well for normal machines because this work can be amortized over a long period of use or be performed when the machine is idle. Exam PCs, however, are never idle and are only used in a short time slot.

Exam-Ready images should meet the following criteria:

  • Usable within 30 seconds after login with cold-start: the student must be able to start their exam quickly. Keep in mind that this includes cold-starting from a new Windows profile.
  • No auto-updating: keep the examination environment static and auditable
  • No non-critical background tasks: any optimizations performed in the background should be disabled (e.g., indexing or filesystem scanning).

Most commonly used imaging and packaging software is not suitable for Exam-Ready images. Therefore, we recommend decoupling these images from your normal image building/packaging pipeline.

Avdcli

Exam-Ready images should not auto-update, which means that keeping your images up to date is a reoccurring task. To simplify, standardize and automate the image building process, we recommend you to use our avdcli tool. This tool can build and update optimized exam-ready images from the command line. avdcli integrates with Azure Image Builder to make your image building pipeline fully automated.

The installation and configuration of images is defined in PowerShell scripts that are automatically executed during the image building process. To organize these scripts and allow for reuse of components, the avdcli uses a layering approach. Each software package gets its own layer of scripts and configuration, which then can be combined in a final image. These layers can be updated individually and shared amongst the community.

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