Modifying xml definition of a running KVM domain via script

LinuxGuru-Wannabe asked:

How can I modify the xml definition of a VM over ssh?
I know that I can do this interactively by logging into the host and using:

virsh edit <domain name>

But I want to automate this modification of xml using a script that runs on a remote host and then executes commands over ssh on the KVM box.

From what I have observed is that virsh edit is opening the default editor (vi in my case) for me to edit the file. I want to somehow overwrite this file (which is interactively opened by virsh edit command) with vm definition contained in another text file.

I have found threads on how text can be piped to vi using:

cat <file name> | vi -

But that wont work in my case since,

  1. virsh is opening up default editor with arguments that I have no control over. (or at least I don’t know how to modify those arguments)
  2. The default editor could be different on different KVM boxes.

Thanks in advance for helping out.

Edit: Just wanted to make clear that I do not have an option to power off the VM and redefine it. I want to modify a running domain.

My answer:

Use virsh dumpxml to get the XML, and then virsh define to replace the domain definition with your modifications.

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