Yes, you can use qcow2 images with Xen

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Happy Monday everyone. Today I discovered we can mount QEMU qcow2 images, without converting them to raw first. For example, this would be a typical file based line in a Xen config:

disk = ['file:/path/disk.raw,xvda,w']

For qcow2 images, the syntax is:

disk = ['tap:qcow2:/path/images/disk.qcow2,xvda,w']

Alas, some Linux distros and FreeBSD fail in this configuration. Therefore, a gigantic your mileage may vary warning must be observed before running a test machine with this, even if you live in the rest of the world that now uses the metric system.