KVM api to start virtual machine

Question

I was wondering if there is a KVM API which allows you to start a KVM virtual machine using a simple command, from a python script.

My Python script performs a series of checks to see whether or not we need to start a specific VM, and I would like to start a VM if I need to.

All I need now is to find the API calls, but I can't find a simple call to start them within the libvirt website. Does anybody know if this is possible?

Answer 1

You can use the create() function from the python API bindings of libvirt:

import libvirt

#connect to hypervisor running on localhost
conn = libvirt.open('qemu:///system')

dom0 = conn.lookupByName('my-vm-1')
dom0.create()

basically the python API is the C API, called by libvirt.C_API_CALL minus the virConnect part or conn.C_API_CALL minus the virDomain part.

see the libvirt API create call and here.

Answer 2

The simplest way, though probably not the best recommended way is to use the os.system using python to invoke qemu-kvm. This method will have the disadvantage that you will have to manually manage the VM.

Using libvirt, you will first have to define a domain by calling virt-install.

virt-install \
         --connect qemu:///system \
         --virt-type kvm \
         --name MyNewVM \
         --ram 512 \
         --disk path=/var/lib/libvirt/images/MyNewVM.img,size=8 \
         --vnc \
         --cdrom /var/lib/libvirt/images/Fedora-14-x86_64-Live-KDE.iso \
         --network network=default,mac=52:54:00:9c:94:3b \
         --os-variant fedora14

I have picked this directly from http://wiki.libvirt.org/page/VM_lifecycle

Once you create the domain, you can use virsh start MyNewVM to start the VM. Using this method, it is much easier to manage the VM.