Red Hat Container Development Kit (CDK) With Nested KVM

Red Hat Container Development Kit (CDK) With Nested KVM


If you are like me, you probably prefer to install new and exploratory software in a fresh virtual machine (VM) or container to insulate your laptop/desktop from software pollution (TM). Red Hat Container Development Kit (CDK) relies on virtualization to create a Red Hat Enterprise Linux (RHEL) virtual machine to run OpenShift (based on Kubernetes). Red Hat specifically supports installation of the CDK on Windows, macOS, and RHEL Server, but if you are running Fedora, RHEL Workstation, or even CentOS, you will run into trouble. If you are not running a supported desktop, you can always use a RHEL Server virtual machine, and this tutorial is for you.

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Setting up KVM on Red Hat Enterprise Linux

Editor’s Note:  If you have a Linux system that runs KVM and would like to try Red Hat Enterprise Linux on KVM, follow our KVM Get started guide, http://developers.redhat.com/products/rhel/get-started/#tab-kvm

The kernel-based Virtual Machine (KVM) is a virtualization infrastructure many have become familiar with throughout the industry. This article will guide you through getting a basic KVM hypervisor up and running and ready for use. In order to fully utilize the KVM, you will need a CPU that has virtualization extensions, and these will need to be enabled in the BIOS of the machine you’re working on. In general, you’ll need to look to enable VT-X or AMD-V depending on your system architecture.

Our Objectives

  • Set up a RedHat Enterprise Linux (RHEL 7.2) server
  • Identify whether Virtualisation extensions are present
  • Install KVM and associated software components
  • Networking Considerations
  • Configure VNC
  • Demonstrate how to fire up a new Virtual Machine running on the KVM hypervisor
  • Listing existing Virtual Machines

Installing RHEL

For the purposes of this article, I’m going to be showing you how to manually install KVM from the command line, rather than opt to have it installed as part of the RHEL installation process. This will allow us to fine tune the installation by only installing what we need, and it also gives us a better understanding of how everything fits together. With this in mind, we will be working on the basis that you have opted for a ‘minimal install’ of RHEL. After first boot, you will want to register to the Red Hat network to receive updates and download software. This can be done by running the following command:

subscription-manager register –auto-attach

You will be prompted to enter your username and password.

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Live Migrating QEMU-KVM Virtual Machines

Live migrating virtual machines is an interesting ongoing topic for virtualization: guests keep getting bigger (more vCPUs, more RAM), and demands on the uptime for guests keep getting stricter (no long pauses between a VM migrating from one host to another).

This discussion will go through the simple design from the early days of live migration in the QEMU/KVM hypervisor, how it has been tweaked and  optimized to where it is now, and where we’re going in the future. It will discuss how live migration actually works, the constraints within which it all has to work, and how the design keeps needing new thought to cover the latest requirements.

The discussion will also cover known unknowns, i.e TODO items, for interested people to step up.

This article is based on a presentation I recently delivered at the devconf.cz conference.  The PDF version of slides are available here, but you won’t need them to follow this post.  The format followed for this article is: a textual representation of the slides, followed by a description of the content, roughly corresponding to what I would say during the presentation.

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