Script to create/start/stop/destroy many CoreOS VMs running on a KVM host (referenced from http://www.beginswithdata.com/2016/12/30/centos7-kvm-coreos/)

manage.py

#! /usr/bin/python
################################################################################
# Manage (create/start/stop/undefine) CoreOS VMs on CentOS 7 using              #
# QEMU/KVM/libvirt.  Makes it easy to create/undefine container hosts           #
# for lab purposes.                                                            #
#                                                                              #
# For more info see this blog post:                                            #
# http://beginswithdata.com/2016/12/30/centos7-kvm-coreos/                     #
#                                                                              #
# Copyright (c) Chris Madden. All rights reserved.                             #
# Specifications subject to change without notice.                             #
################################################################################

import sys, argparse, os, shutil, subprocess, errno, socket, logging

parser = argparse.ArgumentParser(description='Manage some container host VMs.')
parser.add_argument('--prefix', dest='prefix', help='Prefix hostname for managed VMs', required=True)
parser.add_argument('--start', dest='start', type=int, help='Suffix number for managed VMs', required=True)
parser.add_argument('--count', dest='count', type=int, help='Count of VMs to manage', required=True)
parser.add_argument('--action',dest='action', help='Action to take [create|start|stop|undefine]', required=True)
parser.add_argument('--ip', dest='ip', help='Starting IP address if creating VMs or keyword "dns"')
args = parser.parse_args()

img_name = 'os.img'

dir_path = os.path.dirname(os.path.realpath(__file__))
logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.DEBUG)

# Loop though for quantity of VMs to manage
for i in range(args.count):
   vmname = str(args.prefix) + str(args.start + i )
   vm_path = dir_path + '/../' + vmname

   # create logic
   if args.action == 'create':

      logging.info(vmname + ": Creating...")

      # Determine IP address for VM
      if args.ip == 'dns':
         try:
            ip = socket.gethostbyname(vmname)
         except Exception as exc:
            logging.error(vmname + ': DNS lookup failed.')
            continue
      else:
         try:
            ip_list = args.ip.split('.')
         except Exception as exc:
            logging.error(vmname + ': IP address not provided or not parsable')
            exit()
         ip = '.'.join(ip_list[:3]) + '.' + str(int(ip_list[3]) + i)

      logging.info(vmname + ": Using IP " + ip)

      # Check if IP is in use before starting just in case...
      if (os.system("ping -c 1 -W 3 " + vmname + "> /dev/null") == 0):
         logging.error(vmname + ': IP address is pingable; skipping creation')
         continue
    
      # Create subdir
      try:
         os.makedirs(vm_path)
      except OSError as exc:
         if exc.errno == errno.EEXIST:
            logging.warning(vmname + ': Skipping creation because the storage directory already exists')
            continue
         else:
            raise

      # Create cloud-config file for VM doing a search/replace from template
      logging.info(vmname + ": Creating cloud-config")
      with open(dir_path + '/user_data', 'r') as file :
         filedata = file.read()
      filedata = filedata.replace('@@IP@@', ip)
      filedata = filedata.replace('@@VMNAME@@', vmname)
      with open(vm_path + '/user_data', 'w') as file:
         file.write(filedata)

      # Generate ISO 
      logging.info(vmname + ": Creating ISO image of cloud-config")
      os.makedirs('/tmp/new-drive/openstack/latest')
      shutil.copy(vm_path + '/user_data', '/tmp/new-drive/openstack/latest/user_data')
      subprocess.call(['mkisofs', '-quiet', '-input-charset', 'iso8859-1', '-R', '-V', 'config-2', '-o', vm_path + '/configdrive.iso', '/tmp/new-drive'])
      shutil.rmtree('/tmp/new-drive')

      # Copy master image in place
      logging.info(vmname + ": Copying master boot image for VM")
      shutil.copyfile(dir_path + '/' + img_name, vm_path + '/' + img_name)

      # Create and start VM
      vi_cmd = []
      vi_cmd.extend(['virt-install','--connect', 'qemu:///system'])
      vi_cmd.extend(['--import', '--name', vmname])
      vi_cmd.extend(['--ram', '1024', '--vcpus', '1'])
      vi_cmd.extend(['--os-type=linux', '--os-variant=virtio26'])
      vi_cmd.extend(['--disk', 'path=' + vm_path + '/' + img_name + ',format=raw,bus=virtio'])
      vi_cmd.extend(['--disk', 'path=' + vm_path + '/configdrive.iso,device=cdrom,format=raw,bus=ide']) 
      vi_cmd.extend(['--network=bridge=bridge0'])
      vi_cmd.extend(['--accelerate'])
      vi_cmd.extend(['--graphics', "vnc,listen=0.0.0.0"])
      vi_cmd.extend(['--noautoconsole'])
      subprocess.call(vi_cmd)
      logging.info(vmname + ": VM created and booting...")

   # stop logic (incl undefine)
   if args.action in [ 'stop', 'undefine']:
      logging.info(vmname + ": Stopping...")
      subprocess.call(['virsh', 'shutdown', vmname])

   # undefine logic
   if args.action == 'undefine':
      logging.info(vmname + ": Undefining...")
      subprocess.call(['virsh', 'undefine', vmname])
      shutil.rmtree(vm_path)

   # start logic
   if args.action == 'start':
      logging.info(vmname + ": Starting...")
      subprocess.call(['virsh', 'start', vmname])



### CLI equivalents of the above
#mkdir -p /tmp/new-drive/openstack/latest
#cp coreos1/user_data /tmp/new-drive/openstack/latest/user_data
#mkisofs -R -V config-2 -o coreos1/configdrive.iso /tmp/new-drive
#rm -fr /tmp/new-drive


#virt-install --connect qemu:///system \
#--import --name coreos1 \
#--ram 1024 --vcpus 1 \
#--os-type=linux --os-variant=virtio26 \
#--disk path=/vm-storage/coreos1/os.img,format=raw,bus=virtio \
#--disk path=/vm-storage/coreos1/configdrive.iso,device=cdrom,format=raw,bus=ide \
#--network=bridge=bridge0 \
#--accelerate \
#--graphics vnc,listen=0.0.0.0 \
#--noautoconsole