Libvirt on the bin

KVM Guests: Graceful Shutdown

Mon, 06 Feb 2012 00:00:00 +0000

So a fairly trivial (but critical) aspect of using KVM is of course performing graceful shutdowns of your domains, without having to reach inside of the guest to perform the shutdown. Now when it comes to turning off your guests you have two ways of proceeding (with virsh)…

bash

virsh destroy vmname

Which is a HARD power off of your guest. This is the same as pulling the power cord from the wall, nothing is shutdown, but the noise stops just the same. This method can result in data corruption if writes are interrupted.

Linux-KVM Management: Live Migration Without Shared Storage

Tue, 16 Aug 2011 00:00:00 +0000

Everyday I learn something new about Linux-KVM, this is why I love this platform. Today we are going to talk about Live Migration. The kicker? Shared storage not required. Now please keep in mind that just because shared storage is not required, doesn’t mean there is not a benefit to it. Shared storage will accelerate this process, since the data will not have to move. However virtualization is all about flexibility and so is Linux for that matter, so why shouldn’t we be able to make the choice? That said this process is not documented by the libvirt team, as such it sounds like an “undocumented” feature. Please use this at your own risk, and for heaven’s sake please test and understand thoroughly before using this in production.

Linux-KVM: Managing Disk Images

Wed, 16 Mar 2011 00:00:00 +0000

Disk images have long been the traditional form of storage for virtualized environments, they are essentially containers in the form of a file on the host’s file system. These files can be either fully allocated or sparsely allocated at time of disk creation, a fully allocated 20GB disk image will take up 20GB of storage on the host file system, a sparsely allocated 20GB disk image will only take up as much storage on the host file system as has actually been written inside of the disk, so if you have a newly created sparse file the file will be just a few KB in size.

KVM Guests: Manipulating Libvirt XML for Guest Creation

Tue, 15 Mar 2011 00:00:00 +0000

Today we are going to discuss using the underlying XML which libvirt uses to define a VM to either create VMs or to make simple changes. This method has the advantage of more control over what you are creating, although it is more manual. Now first off, when you use virt-install, virt-manager, or another tool which uses libvirt under the covers an XML file is created for every VM that you define, libvirt stores these in /etc/libvirt/qemu/ and names them vmname.xml.