These are short posts on how to connect to qemu/KVM via libvirt using Python binding. Ability to talk to the hypervisor helps in various automation tasks. In this post, we show how to connect to hypervisor and display domain details. Its assumed that you have Qemu/KVM and have installed libvirt-python package. If not, its yum install libvirt-python to install it.

import libvirt
import sys

#Open a readonly connection to libvirt
conn = libvirt.openReadOnly(None)

if conn == None:
    Logger.critical( 'Could not connect to the hypervisor')
    sys.exit(1)
try:
    dom = conn.lookupByName("centos_vm")
except:
    Logger.critical( 'Could not find the domain')
    sys.exit(1)
print ("Domain : id %d running %s state = %d" % (dom.ID(), dom.OSType(), dom.state()[0]))
print (dom.info())

Output

Domain 0: id -1 running hvm state = 5
[5, 2097152L, 0L, 2, 0L]

From libvirt source code:

# virDomainState (dom.state()[0])
VIR_DOMAIN_NOSTATE     = 0 # no state
VIR_DOMAIN_RUNNING     = 1 # the domain is running
VIR_DOMAIN_BLOCKED     = 2 # the domain is blocked on resource
VIR_DOMAIN_PAUSED      = 3 # the domain is paused by user
VIR_DOMAIN_SHUTDOWN    = 4 # the domain is being shut down
VIR_DOMAIN_SHUTOFF     = 5 # the domain is shut off
VIR_DOMAIN_CRASHED     = 6 # the domain is crashed
VIR_DOMAIN_PMSUSPENDED = 7 # the domain is suspended by guest power management

More Help

Run this command to print out the entire libvirt API.

python -c "import libvirt; help(libvirt)" > help.txt

Other ways to display state names:

domain_state_name = {  libvirt.VIR_DOMAIN_NOSTATE     : "no state",
                       libvirt.VIR_DOMAIN_RUNNING     : "running",
                       libvirt.VIR_DOMAIN_BLOCKED     : "idle",
                       libvirt.VIR_DOMAIN_PAUSED      : "paused",
                       libvirt.VIR_DOMAIN_SHUTDOWN    : "in shutdown",
                       libvirt.VIR_DOMAIN_SHUTOFF     : "shut off",
                       libvirt.VIR_DOMAIN_CRASHED     : "crashed",
                       libvirt.VIR_DOMAIN_PMSUSPENDED : "suspended by PM" }

print("Current State:", domain_state_name[dom.state()[0]])

References

http://www.ibm.com/developerworks/library/os-python-kvm-scripting1/