I want to call out a stellar article that told me exactly what I needed to do in order to use virt-install and cloud-init to launch a cloud-image. The only thing I have to add is the caveat that the #cloud-config comment at the top of the user-data file is required. The system will ignore the file if it does not start with that comment. This is the easiest way I know to launch a brand new VM.
The following xmllint XPath query will pull out the name of the backing file for a VM named fedora-server-36 and an external snapshot named fedora-36-post-install,
virsh snapshot-dumpxml fedora-server-36 fedora-server-36-post-install | xmllint --xpath "string(//domainsnapshot/disks/disk[@snapshot='external']/source/@file)" - |
The string function extracts the attribute value.
This value can be used in the process of using or deleting the snapshot.
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 |
I have a fresh install of Fedora 35 on a lab machine. I want to run a virtual machine on it. I have ssh access to the root account and a public key copied over.
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Continue readingAnsible exists to help automate the time consuming repeated tasks that technologist depend upon. One very common jobs is to create and tear down a virtual machine. While cloud technologies have made this possible to perform remotely, there are many times when I’ve needed to setup and tear down virtual machines on systems that were stand alone Linux servers. In this case, the main interfaces to the machine are ssh and libvirt. I recently worked through an Ansible role to setup and tear down an virtual machine via libvirt, and I’d like to walk through it, and record my reasons for some of the decisions I made.
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I can connect to the system libvirtd on my system without password. I set this up some time ago, and forgot how, so figured I would document it.
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After the previous two days debugging, Simo Sorce suggested that I need to tell the OS to show all AVCs, some are hidden by default.
Trying to troubleshoot the issues from Yesterday’s SELinux errors.
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