Category Archives: Xen

Adding libvirt networking to my Perl YAML-based KVM Provisioner

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Introduction

Hello World! It has been a few months since I’ve posted anything here, due to taking on a new role at work and having to learn new skills for it.

In a previous post, I described writing a Perl provisioning script for creating KVM virtual machines. The list of machines and attributes are defined in a YAML file, and then “spun up” using virt-install and cloud-init. It performs a similar role to Terraform, but is simpler and more focused. Mainly I wrote it to improve my Perl skills and learn more about libvirt, not replace Terraform entirely.

However, I later realized that the usefulness of this script is diminished by the fact that it can’t create libvirt NAT networks or provision virtual machines with static IP addresses. My first version used Dnsmasq for assigning addresses to the VMs; I’ve now soured on this approach. Instead, I’ve decided to re-factor this script to use cloud-init to assign a static IP address to the VM. This post will talk about the rewrite of the script.

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Installing Debian 12 and 13 on a ProLiant DL360 G7

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Introduction

In a previous post, I discussed my experiences with installing a recent version of Enterprise Linux, AlmaLinux 9, on an e-waste HP ProLiant DL360 G7. I also discussed updating the firmware for the Integrated Lights-Out (iLO) remote management tool and the HP Smart Array controller, and installing the OS over the network from the iLO console. In this post I will perform some of these tasks, but for Debian instead. I will also incorporate some knowledge from my previous posts on virtualization, networking, and Ansible.

These exercises were performed on a ProLiant DL360 G7, but it’s likely that they will work on other Proliant servers.

A ProLiant DL360 G7 at the bottom of an e-waste stack.

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Writing a Perl YAML-based Xen Provisioner

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Introduction

In my previous post on the Xen hypervisor, I mentioned my interest in writing a Perl provisioning tool for Xen that functions similarly to Terraform. This tool isn’t meant to replace Terraform (nor claim that it is superior), but there doesn’t seem to be a Terraform provisioner for standalone Xen. Furthermore, sometimes it makes more sense to code a custom tool that does exactly what you want, versus trying to adapt an existing tool, especially a complicated one like Terraform. This tool has a single purpose: to give the user the ability to define a set of virtual machines with their specs (RAM, disk space, static IP addresses, etc.) and spin up these VMs with a single command, as well as take them down when they are no longer needed.

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Building my own Xen images

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In light of a few issues I’ve discovered with this post, I wouldn’t suggest that you use it as a guide. However, I’m leaving it up anyway, in case it is of use to someone. Instead, I recommend running pre-built cloud images from the OS vendor. I also recommend running using KVM for Enterprise Linux instead of Xen.

In my last post on Xen, I discussed using pre-built cloud images from Debian and AlmaLinux to create Xen virtual machines. These are convenient to use, but might not be ideal for certain use cases. For example, you might want certain packages to be included or excluded from your image, minimizing or even eliminating the role of cloud-init. Or for security reasons, you might not want to run an image from the internet on your local network. In this post, I will discuss how I built Xen images for AlmaLinux and Debian.

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Xen Paravirtualization Part 2 – Debian

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Introduction

In my last post, I explored running the Xen hypervisor on two deprecated versions of CentOS. In this post, I return to the present, setting up Xen on Debian 12 and 13, while using some of the techniques learned in the previous post. As is the case with a lot of my posts, this will involve a variety of topics, including Linux, networking, Perl, cloud-init, and more.

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A Retrospective: Xen Paravirtualization Part 1 – CentOS 5 and 6

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Introduction

A blog post about CentOS 5 or 6 isn’t going to excite anyone or show up in many intentional Google searches. CentOS 5 and 6 are 18 and 14 years old respectively in 2025 and are mostly viewed as insecure at this point; they also haven’t reached the point of being “retro cool” yet (and may never be). However, for me there will always be a certain amount of nostalgia for these operating systems, CentOS 5 in particular: it and related Enterprise Linux 5 variants were the first Linux distributions I used in my work—previously I had only used Ubuntu, Debian, and Fedora on the desktop. My first home server also ran CentOS 5, with 6-8 VMs running on a Xen hypervisor in paravirtualized mode. Paravirtualization at the time provided better performance than full virtualization (VMWare ESXi, KVM, VirtualBox, etc.) and allowed running VMs on CPUs that didn’t have virtualization extensions. My main home server at the time supported hardware virtualization, but I was also able to run Xen on some spare systems that did not, such as a Pentium D desktop with only 2GB of RAM. My impressions at the time were that Xen was lightweight, resilient, and easy to configure. The bridged network functioned right out of the box and the machine config files consisted of only a few lines. Thus it was with some reluctance that I eventually rebuilt my lab with CentOS 6 and KVM. Since then, I’ve always been a KVM user and my experience with it has been mostly positive. Still, my perpetual dislike of libvirt’s XML files and excessive number of virsh subcommands has made me nostalgic for my first lab setup with Xen. In this post I will fire up Xen once again on both CentOS 5 and 6, while doing a little bit of scripting to make it more interesting.

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