Parsing libvirt xmldump using xpath

In a recent article, I saw yet another example of using grep to pull information out of xml, and then to manually look for a field. However, XML is structured, and with XPath, we can pull out exactly what we need.

virsh dumpxml fedora-server-36 | xmllint --xpath "//domain/devices/disk[@device='disk']"  -

That will produce output like this:

<disk type="file" device="disk">
      <driver name="qemu" type="qcow2" discard="unmap"/>
      <source file="/var/lib/libvirt/images/fedora-server-36.qcow2"/>
      <target dev="vda" bus="virtio"/>
      <address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
</disk>

Note that I did more in my XPath than required by the original article. I wanted to show an example of querying based on an attribute inside the selected node.

Update: Here is an example for what is done later in the article: pull the path out of the pool xml.

virsh pool-dumpxml default |  xmllint --xpath "//pool/target/path/text()"  -
/var/lib/libvirt/images

ipxe.efi for aarch64

To make the AARCH64 ipxe process work using bifrost, I had to

git clone https://github.com/ipxe/ipxe.git
cd ipxe/src/
make bin-arm64-efi/snponly.efi ARCH=arm64
sudo cp bin-arm64-efi/snponly.efi /var/lib/tftpboot/ipxe.efi

This works for the Ampere reference implementation servers that use a Mellanox network interface card, which supports (only) snp.

Network traffic for an Ironic Node

I’ve set up a second cluster, and the Ironic nodes are not PXE booting. Specifically, if I watch the nodes boot via an IPMI serial-on-lan console, I see that they send out a DHCP request and never get a response back.

This is a problem I am familiar with from my days at Penguin. Time to dig in and understand the networking setup on the controller to see why it is not getting the packet. Or, possibly, why it is getting it and the response is getting dropped.

I have another cluster that is working properly, and I am going to look at the setup there to try and contrast it with the broken set up, and figure out my problem.

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Automating Baremetal Node Creation for Ironic

Sometime your shell scripts get out of control. Sometimes you are proud of them. Sometimes….both.

I need to be able to re-add a bunch of nodes to an OpenStack cluster on a regular basis. Yes, I could do this with Ansible, but, well, Ansible is great for doing something via SSH, and this just needs to be done here and now. So shell is fine.

This started as a one liner, and got a bit bigger.

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