Synnefo » snf-ganeti

#

#

# Copyright (C) 2008, 2009, 2010 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""KVM hypervisor

"""

import errno

import os

import os.path

import re

import tempfile

import time

import logging

import pwd

import struct

import fcntl

import shutil

from ganeti import utils

from ganeti import constants

from ganeti import errors

from ganeti import serializer

from ganeti import objects

from ganeti import uidpool

from ganeti import ssconf

from ganeti.hypervisor import hv_base

from ganeti import netutils

from ganeti.utils import wrapper as utils_wrapper

_KVM_NETWORK_SCRIPT = constants.SYSCONFDIR + "/ganeti/kvm-vif-bridge"

# TUN/TAP driver constants, taken from <linux/if_tun.h>

# They are architecture-independent and already hardcoded in qemu-kvm source,

# so we can safely include them here.

TUNSETIFF = 0x400454ca

TUNGETIFF = 0x800454d2

TUNGETFEATURES = 0x800454cf

IFF_TAP = 0x0002

IFF_NO_PI = 0x1000

IFF_VNET_HDR = 0x4000

def _ProbeTapVnetHdr(fd):

  """Check whether to enable the IFF_VNET_HDR flag.

  To do this, _all_ of the following conditions must be met:

   1. TUNGETFEATURES ioctl() *must* be implemented

   2. TUNGETFEATURES ioctl() result *must* contain the IFF_VNET_HDR flag

   3. TUNGETIFF ioctl() *must* be implemented; reading the kernel code in

      drivers/net/tun.c there is no way to test this until after the tap device

      has been created using TUNSETIFF, and there is no way to change the

      IFF_VNET_HDR flag after creating the interface, catch-22! However both

      TUNGETIFF and TUNGETFEATURES were introduced in kernel version 2.6.27,

      thus we can expect TUNGETIFF to be present if TUNGETFEATURES is.

   @type fd: int

   @param fd: the file descriptor of /dev/net/tun

  """

  req = struct.pack("I", 0)

  try:

    res = fcntl.ioctl(fd, TUNGETFEATURES, req)

  except EnvironmentError:

    logging.warning("TUNGETFEATURES ioctl() not implemented")

    return False

  tunflags = struct.unpack("I", res)[0]

  if tunflags & IFF_VNET_HDR:

    return True

  else:

    logging.warning("Host does not support IFF_VNET_HDR, not enabling")

    return False

def _OpenTap(vnet_hdr=True):

  """Open a new tap device and return its file descriptor.

  This is intended to be used by a qemu-type hypervisor together with the -net

  tap,fd=<fd> command line parameter.

  @type vnet_hdr: boolean

  @param vnet_hdr: Enable the VNET Header

  @return: (ifname, tapfd)

  @rtype: tuple

  """

  try:

    tapfd = os.open("/dev/net/tun", os.O_RDWR)

  except EnvironmentError:

    raise errors.HypervisorError("Failed to open /dev/net/tun")

  flags = IFF_TAP | IFF_NO_PI

  if vnet_hdr and _ProbeTapVnetHdr(tapfd):

    flags |= IFF_VNET_HDR

  # The struct ifreq ioctl request (see netdevice(7))

  ifr = struct.pack("16sh", "", flags)

  try:

    res = fcntl.ioctl(tapfd, TUNSETIFF, ifr)

  except EnvironmentError:

    raise errors.HypervisorError("Failed to allocate a new TAP device")

  # Get the interface name from the ioctl

  ifname = struct.unpack("16sh", res)[0].strip("\x00")

  return (ifname, tapfd)

class KVMHypervisor(hv_base.BaseHypervisor):

  """KVM hypervisor interface"""

  CAN_MIGRATE = True

  _ROOT_DIR = constants.RUN_GANETI_DIR + "/kvm-hypervisor"

  _PIDS_DIR = _ROOT_DIR + "/pid" # contains live instances pids

  _UIDS_DIR = _ROOT_DIR + "/uid" # contains instances reserved uids

  _CTRL_DIR = _ROOT_DIR + "/ctrl" # contains instances control sockets

  _CONF_DIR = _ROOT_DIR + "/conf" # contains instances startup data

  _NICS_DIR = _ROOT_DIR + "/nic" # contains instances nic <-> tap associations

  # KVM instances with chroot enabled are started in empty chroot directories.

  _CHROOT_DIR = _ROOT_DIR + "/chroot" # for empty chroot directories

  # After an instance is stopped, its chroot directory is removed.

  # If the chroot directory is not empty, it can't be removed.

  # A non-empty chroot directory indicates a possible security incident.

  # To support forensics, the non-empty chroot directory is quarantined in

  # a separate directory, called 'chroot-quarantine'.

  _CHROOT_QUARANTINE_DIR = _ROOT_DIR + "/chroot-quarantine"

  _DIRS = [_ROOT_DIR, _PIDS_DIR, _UIDS_DIR, _CTRL_DIR, _CONF_DIR, _NICS_DIR,

           _CHROOT_DIR, _CHROOT_QUARANTINE_DIR]

  PARAMETERS = {

    constants.HV_KERNEL_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_INITRD_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_ROOT_PATH: hv_base.NO_CHECK,

    constants.HV_KERNEL_ARGS: hv_base.NO_CHECK,

    constants.HV_ACPI: hv_base.NO_CHECK,

    constants.HV_SERIAL_CONSOLE: hv_base.NO_CHECK,

    constants.HV_VNC_BIND_ADDRESS:

      (False, lambda x: (netutils.IP4Address.IsValid(x) or

                         utils.IsNormAbsPath(x)),

       "the VNC bind address must be either a valid IP address or an absolute"

       " pathname", None, None),

    constants.HV_VNC_TLS: hv_base.NO_CHECK,

    constants.HV_VNC_X509: hv_base.OPT_DIR_CHECK,

    constants.HV_VNC_X509_VERIFY: hv_base.NO_CHECK,

    constants.HV_VNC_PASSWORD_FILE: hv_base.OPT_FILE_CHECK,

    constants.HV_KVM_FLOPPY_IMAGE_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_CDROM_IMAGE_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_KVM_CDROM2_IMAGE_PATH: hv_base.OPT_FILE_CHECK,

    constants.HV_BOOT_ORDER:

      hv_base.ParamInSet(True, constants.HT_KVM_VALID_BO_TYPES),

    constants.HV_NIC_TYPE:

      hv_base.ParamInSet(True, constants.HT_KVM_VALID_NIC_TYPES),

    constants.HV_DISK_TYPE:

      hv_base.ParamInSet(True, constants.HT_KVM_VALID_DISK_TYPES),

    constants.HV_KVM_CDROM_DISK_TYPE:

      hv_base.ParamInSet(False, constants.HT_KVM_VALID_DISK_TYPES),

    constants.HV_USB_MOUSE:

      hv_base.ParamInSet(False, constants.HT_KVM_VALID_MOUSE_TYPES),

    constants.HV_MIGRATION_PORT: hv_base.NET_PORT_CHECK,

    constants.HV_MIGRATION_BANDWIDTH: hv_base.NO_CHECK,

    constants.HV_MIGRATION_DOWNTIME: hv_base.NO_CHECK,

    constants.HV_MIGRATION_MODE: hv_base.MIGRATION_MODE_CHECK,

    constants.HV_USE_LOCALTIME: hv_base.NO_CHECK,

    constants.HV_DISK_CACHE:

      hv_base.ParamInSet(True, constants.HT_VALID_CACHE_TYPES),

    constants.HV_SECURITY_MODEL:

      hv_base.ParamInSet(True, constants.HT_KVM_VALID_SM_TYPES),

    constants.HV_SECURITY_DOMAIN: hv_base.NO_CHECK,

    constants.HV_KVM_FLAG:

      hv_base.ParamInSet(False, constants.HT_KVM_FLAG_VALUES),

    constants.HV_VHOST_NET: hv_base.NO_CHECK,

    constants.HV_KVM_USE_CHROOT: hv_base.NO_CHECK,

    constants.HV_MEM_PATH: hv_base.OPT_DIR_CHECK,

    }

  _MIGRATION_STATUS_RE = re.compile('Migration\s+status:\s+(\w+)',

                                    re.M | re.I)

  _MIGRATION_INFO_MAX_BAD_ANSWERS = 5

  _MIGRATION_INFO_RETRY_DELAY = 2

  _VERSION_RE = re.compile(r"\b(\d+)\.(\d+)\.(\d+)\b")

  ANCILLARY_FILES = [

    _KVM_NETWORK_SCRIPT,

    ]

  def __init__(self):

    hv_base.BaseHypervisor.__init__(self)

    # Let's make sure the directories we need exist, even if the RUN_DIR lives

    # in a tmpfs filesystem or has been otherwise wiped out.

    dirs = [(dname, constants.RUN_DIRS_MODE) for dname in self._DIRS]

    utils.EnsureDirs(dirs)

  @classmethod

  def _InstancePidFile(cls, instance_name):

    """Returns the instance pidfile.

    """

    return utils.PathJoin(cls._PIDS_DIR, instance_name)

  @classmethod

  def _InstanceUidFile(cls, instance_name):

    """Returns the instance uidfile.

    """

    return utils.PathJoin(cls._UIDS_DIR, instance_name)

  @classmethod

  def _InstancePidInfo(cls, pid):

    """Check pid file for instance information.

    Check that a pid file is associated with an instance, and retrieve

    information from its command line.

    @type pid: string or int

    @param pid: process id of the instance to check

    @rtype: tuple

    @return: (instance_name, memory, vcpus)

    @raise errors.HypervisorError: when an instance cannot be found

    """

    alive = utils.IsProcessAlive(pid)

    if not alive:

      raise errors.HypervisorError("Cannot get info for pid %s" % pid)

    cmdline_file = utils.PathJoin("/proc", str(pid), "cmdline")

    try:

      cmdline = utils.ReadFile(cmdline_file)

    except EnvironmentError, err:

      raise errors.HypervisorError("Can't open cmdline file for pid %s: %s" %

                                   (pid, err))

    instance = None

    memory = 0

    vcpus = 0

    arg_list = cmdline.split('\x00')

    while arg_list:

      arg =  arg_list.pop(0)

      if arg == "-name":

        instance = arg_list.pop(0)

      elif arg == "-m":

        memory = int(arg_list.pop(0))

      elif arg == "-smp":

        vcpus = int(arg_list.pop(0))

    if instance is None:

      raise errors.HypervisorError("Pid %s doesn't contain a ganeti kvm"

                                   " instance" % pid)

    return (instance, memory, vcpus)

  def _InstancePidAlive(self, instance_name):

    """Returns the instance pidfile, pid, and liveness.

    @type instance_name: string

    @param instance_name: instance name

    @rtype: tuple

    @return: (pid file name, pid, liveness)

    """

    pidfile = self._InstancePidFile(instance_name)

    pid = utils.ReadPidFile(pidfile)

    alive = False

    try:

      cmd_instance = self._InstancePidInfo(pid)[0]

      alive = (cmd_instance == instance_name)

    except errors.HypervisorError:

      pass

    return (pidfile, pid, alive)

  def _CheckDown(self, instance_name):

    """Raises an error unless the given instance is down.

    """

    alive = self._InstancePidAlive(instance_name)[2]

    if alive:

      raise errors.HypervisorError("Failed to start instance %s: %s" %

                                   (instance_name, "already running"))

  @classmethod

  def _InstanceMonitor(cls, instance_name):

    """Returns the instance monitor socket name

    """

    return utils.PathJoin(cls._CTRL_DIR, "%s.monitor" % instance_name)

  @classmethod

  def _InstanceSerial(cls, instance_name):

    """Returns the instance serial socket name

    """

    return utils.PathJoin(cls._CTRL_DIR, "%s.serial" % instance_name)

  @staticmethod

  def _SocatUnixConsoleParams():

    """Returns the correct parameters for socat

    If we have a new-enough socat we can use raw mode with an escape character.

    """

    if constants.SOCAT_USE_ESCAPE:

      return "raw,echo=0,escape=%s" % constants.SOCAT_ESCAPE_CODE

    else:

      return "echo=0,icanon=0"

  @classmethod

  def _InstanceKVMRuntime(cls, instance_name):

    """Returns the instance KVM runtime filename

    """

    return utils.PathJoin(cls._CONF_DIR, "%s.runtime" % instance_name)

  @classmethod

  def _InstanceChrootDir(cls, instance_name):

    """Returns the name of the KVM chroot dir of the instance

    """

    return utils.PathJoin(cls._CHROOT_DIR, instance_name)

  @classmethod

  def _InstanceNICDir(cls, instance_name):

    """Returns the name of the directory holding the tap device files for a

    given instance.

    """

    return utils.PathJoin(cls._NICS_DIR, instance_name)

  @classmethod

  def _InstanceNICFile(cls, instance_name, seq):

    """Returns the name of the file containing the tap device for a given NIC

    """

    return utils.PathJoin(cls._InstanceNICDir(instance_name), str(seq))

  @classmethod

  def _TryReadUidFile(cls, uid_file):

    """Try to read a uid file

    """

    if os.path.exists(uid_file):

      try:

        uid = int(utils.ReadOneLineFile(uid_file))

        return uid

      except EnvironmentError:

        logging.warning("Can't read uid file", exc_info=True)

      except (TypeError, ValueError):

        logging.warning("Can't parse uid file contents", exc_info=True)

    return None

  @classmethod

  def _RemoveInstanceRuntimeFiles(cls, pidfile, instance_name):

    """Removes an instance's rutime sockets/files/dirs.

    """

    utils.RemoveFile(pidfile)

    utils.RemoveFile(cls._InstanceMonitor(instance_name))

    utils.RemoveFile(cls._InstanceSerial(instance_name))

    utils.RemoveFile(cls._InstanceKVMRuntime(instance_name))

    uid_file = cls._InstanceUidFile(instance_name)

    uid = cls._TryReadUidFile(uid_file)

    utils.RemoveFile(uid_file)

    if uid is not None:

      uidpool.ReleaseUid(uid)

    try:

      shutil.rmtree(cls._InstanceNICDir(instance_name))

    except OSError, err:

      if err.errno != errno.ENOENT:

        raise

    try:

      chroot_dir = cls._InstanceChrootDir(instance_name)

      utils.RemoveDir(chroot_dir)

    except OSError, err:

      if err.errno == errno.ENOTEMPTY:

        # The chroot directory is expected to be empty, but it isn't.

        new_chroot_dir = tempfile.mkdtemp(dir=cls._CHROOT_QUARANTINE_DIR,

                                          prefix="%s-%s-" %

                                          (instance_name,

                                           utils.TimestampForFilename()))

        logging.warning("The chroot directory of instance %s can not be"

                        " removed as it is not empty. Moving it to the"

                        " quarantine instead. Please investigate the"

                        " contents (%s) and clean up manually",

                        instance_name, new_chroot_dir)

        utils.RenameFile(chroot_dir, new_chroot_dir)

      else:

        raise

  @staticmethod

  def _ConfigureNIC(instance, seq, nic, tap):

    """Run the network configuration script for a specified NIC

    @param instance: instance we're acting on

    @type instance: instance object

    @param seq: nic sequence number

    @type seq: int

    @param nic: nic we're acting on

    @type nic: nic object

    @param tap: the host's tap interface this NIC corresponds to

    @type tap: str

    """

    if instance.tags:

      tags = " ".join(instance.tags)

    else:

      tags = ""

    env = {

      "PATH": "%s:/sbin:/usr/sbin" % os.environ["PATH"],

      "INSTANCE": instance.name,

      "MAC": nic.mac,

      "MODE": nic.nicparams[constants.NIC_MODE],

      "INTERFACE": tap,

      "INTERFACE_INDEX": str(seq),

      "TAGS": tags,

    }

    if nic.ip:

      env["IP"] = nic.ip

    if nic.nicparams[constants.NIC_LINK]:

      env["LINK"] = nic.nicparams[constants.NIC_LINK]

    if nic.nicparams[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED:

      env["BRIDGE"] = nic.nicparams[constants.NIC_LINK]

    result = utils.RunCmd([constants.KVM_IFUP, tap], env=env)

    if result.failed:

      raise errors.HypervisorError("Failed to configure interface %s: %s."

                                   " Network configuration script output: %s" %

                                   (tap, result.fail_reason, result.output))

  def ListInstances(self):

    """Get the list of running instances.

    We can do this by listing our live instances directory and

    checking whether the associated kvm process is still alive.

    """

    result = []

    for name in os.listdir(self._PIDS_DIR):

      if self._InstancePidAlive(name)[2]:

        result.append(name)

    return result

  def GetInstanceInfo(self, instance_name):

    """Get instance properties.

    @type instance_name: string

    @param instance_name: the instance name

    @rtype: tuple of strings

    @return: (name, id, memory, vcpus, stat, times)

    """

    _, pid, alive = self._InstancePidAlive(instance_name)

    if not alive:

      return None

    _, memory, vcpus = self._InstancePidInfo(pid)

    stat = "---b-"

    times = "0"

    return (instance_name, pid, memory, vcpus, stat, times)

  def GetAllInstancesInfo(self):

    """Get properties of all instances.

    @return: list of tuples (name, id, memory, vcpus, stat, times)

    """

    data = []

    for name in os.listdir(self._PIDS_DIR):

      try:

        info = self.GetInstanceInfo(name)

      except errors.HypervisorError:

        continue

      if info:

        data.append(info)

    return data

  def _GenerateKVMRuntime(self, instance, block_devices):

    """Generate KVM information to start an instance.

    """

    pidfile  = self._InstancePidFile(instance.name)

    kvm = constants.KVM_PATH

    kvm_cmd = [kvm]

    # used just by the vnc server, if enabled

    kvm_cmd.extend(['-name', instance.name])

    kvm_cmd.extend(['-m', instance.beparams[constants.BE_MEMORY]])

    kvm_cmd.extend(['-smp', instance.beparams[constants.BE_VCPUS]])

    kvm_cmd.extend(['-pidfile', pidfile])

    kvm_cmd.extend(['-daemonize'])

    if not instance.hvparams[constants.HV_ACPI]:

      kvm_cmd.extend(['-no-acpi'])

    hvp = instance.hvparams

    boot_disk = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_DISK

    boot_cdrom = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_CDROM

    boot_floppy = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_FLOPPY

    boot_network = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_NETWORK

    if hvp[constants.HV_KVM_FLAG] == constants.HT_KVM_ENABLED:

      kvm_cmd.extend(["-enable-kvm"])

    elif hvp[constants.HV_KVM_FLAG] == constants.HT_KVM_DISABLED:

      kvm_cmd.extend(["-disable-kvm"])

    if boot_network:

      kvm_cmd.extend(['-boot', 'n'])

    disk_type = hvp[constants.HV_DISK_TYPE]

    if disk_type == constants.HT_DISK_PARAVIRTUAL:

      if_val = ',if=virtio'

    else:

      if_val = ',if=%s' % disk_type

    # Cache mode

    disk_cache = hvp[constants.HV_DISK_CACHE]

    if disk_cache != constants.HT_CACHE_DEFAULT:

      cache_val = ",cache=%s" % disk_cache

    else:

      cache_val = ""

    for cfdev, dev_path in block_devices:

      if cfdev.mode != constants.DISK_RDWR:

        raise errors.HypervisorError("Instance has read-only disks which"

                                     " are not supported by KVM")

      # TODO: handle FD_LOOP and FD_BLKTAP (?)

      if boot_disk:

        kvm_cmd.extend(['-boot', 'c'])

        if disk_type != constants.HT_DISK_IDE:

          boot_val = ',boot=on'

        else:

          boot_val = ''

        # We only boot from the first disk

        boot_disk = False

      else:

        boot_val = ''

      drive_val = 'file=%s,format=raw%s%s%s' % (dev_path, if_val, boot_val,

                                                cache_val)

      kvm_cmd.extend(['-drive', drive_val])

    #Now we can specify a different device type for CDROM devices.

    cdrom_disk_type = hvp[constants.HV_KVM_CDROM_DISK_TYPE]

    if not cdrom_disk_type:

      cdrom_disk_type = disk_type

    iso_image = hvp[constants.HV_CDROM_IMAGE_PATH]

    if iso_image:

      options = ',format=raw,media=cdrom'

      if boot_cdrom:

        kvm_cmd.extend(['-boot', 'd'])

        if cdrom_disk_type != constants.HT_DISK_IDE:

          options = '%s,boot=on,if=%s' % (options, constants.HT_DISK_IDE)

        else:

          options = '%s,boot=on' % options

      else:

        if cdrom_disk_type == constants.HT_DISK_PARAVIRTUAL:

          if_val = ',if=virtio'

        else:

          if_val = ',if=%s' % cdrom_disk_type

        options = '%s%s' % (options, if_val)

      drive_val = 'file=%s%s' % (iso_image, options)

      kvm_cmd.extend(['-drive', drive_val])

    iso_image2 = hvp[constants.HV_KVM_CDROM2_IMAGE_PATH]

    if iso_image2:

      options = ',format=raw,media=cdrom'

      if cdrom_disk_type == constants.HT_DISK_PARAVIRTUAL:

        if_val = ',if=virtio'

      else:

        if_val = ',if=%s' % cdrom_disk_type

      options = '%s%s' % (options, if_val)

      drive_val = 'file=%s%s' % (iso_image2, options)

      kvm_cmd.extend(['-drive', drive_val])

    floppy_image = hvp[constants.HV_KVM_FLOPPY_IMAGE_PATH]

    if floppy_image:

      options = ',format=raw,media=disk'

      if boot_floppy:

        kvm_cmd.extend(['-boot', 'a'])

        options = '%s,boot=on' % options

      if_val = ',if=floppy'

      options = '%s%s' % (options, if_val)

      drive_val = 'file=%s%s' % (floppy_image, options)

      kvm_cmd.extend(['-drive', drive_val])

    kernel_path = hvp[constants.HV_KERNEL_PATH]

    if kernel_path:

      kvm_cmd.extend(['-kernel', kernel_path])

      initrd_path = hvp[constants.HV_INITRD_PATH]

      if initrd_path:

        kvm_cmd.extend(['-initrd', initrd_path])

      root_append = ['root=%s' % hvp[constants.HV_ROOT_PATH],

                     hvp[constants.HV_KERNEL_ARGS]]

      if hvp[constants.HV_SERIAL_CONSOLE]:

        root_append.append('console=ttyS0,38400')

      kvm_cmd.extend(['-append', ' '.join(root_append)])

    mem_path = hvp[constants.HV_MEM_PATH]

    if mem_path:

      kvm_cmd.extend(["-mem-path", mem_path, "-mem-prealloc"])

    mouse_type = hvp[constants.HV_USB_MOUSE]

    vnc_bind_address = hvp[constants.HV_VNC_BIND_ADDRESS]

    if mouse_type:

      kvm_cmd.extend(['-usb'])

      kvm_cmd.extend(['-usbdevice', mouse_type])

    elif vnc_bind_address:

      kvm_cmd.extend(['-usbdevice', constants.HT_MOUSE_TABLET])

    if vnc_bind_address:

      if netutils.IP4Address.IsValid(vnc_bind_address):

        if instance.network_port > constants.VNC_BASE_PORT:

          display = instance.network_port - constants.VNC_BASE_PORT

          if vnc_bind_address == constants.IP4_ADDRESS_ANY:

            vnc_arg = ':%d' % (display)

          else:

            vnc_arg = '%s:%d' % (vnc_bind_address, display)

        else:

          logging.error("Network port is not a valid VNC display (%d < %d)."

                        " Not starting VNC", instance.network_port,

                        constants.VNC_BASE_PORT)

          vnc_arg = 'none'

        # Only allow tls and other option when not binding to a file, for now.

        # kvm/qemu gets confused otherwise about the filename to use.

        vnc_append = ''

        if hvp[constants.HV_VNC_TLS]:

          vnc_append = '%s,tls' % vnc_append

          if hvp[constants.HV_VNC_X509_VERIFY]:

            vnc_append = '%s,x509verify=%s' % (vnc_append,

                                               hvp[constants.HV_VNC_X509])

          elif hvp[constants.HV_VNC_X509]:

            vnc_append = '%s,x509=%s' % (vnc_append,

                                         hvp[constants.HV_VNC_X509])

        if hvp[constants.HV_VNC_PASSWORD_FILE]:

          vnc_append = '%s,password' % vnc_append

        vnc_arg = '%s%s' % (vnc_arg, vnc_append)

      else:

        vnc_arg = 'unix:%s/%s.vnc' % (vnc_bind_address, instance.name)

      kvm_cmd.extend(['-vnc', vnc_arg])

    else:

      kvm_cmd.extend(['-nographic'])

    monitor_dev = ("unix:%s,server,nowait" %

                   self._InstanceMonitor(instance.name))

    kvm_cmd.extend(['-monitor', monitor_dev])

    if hvp[constants.HV_SERIAL_CONSOLE]:

      serial_dev = ('unix:%s,server,nowait' %

                    self._InstanceSerial(instance.name))

      kvm_cmd.extend(['-serial', serial_dev])

    else:

      kvm_cmd.extend(['-serial', 'none'])

    if hvp[constants.HV_USE_LOCALTIME]:

      kvm_cmd.extend(['-localtime'])

    if hvp[constants.HV_KVM_USE_CHROOT]:

      kvm_cmd.extend(['-chroot', self._InstanceChrootDir(instance.name)])

    # Save the current instance nics, but defer their expansion as parameters,

    # as we'll need to generate executable temp files for them.

    kvm_nics = instance.nics

    hvparams = hvp

    return (kvm_cmd, kvm_nics, hvparams)

  def _WriteKVMRuntime(self, instance_name, data):

    """Write an instance's KVM runtime

    """

    try:

      utils.WriteFile(self._InstanceKVMRuntime(instance_name),

                      data=data)

    except EnvironmentError, err:

      raise errors.HypervisorError("Failed to save KVM runtime file: %s" % err)

  def _ReadKVMRuntime(self, instance_name):

    """Read an instance's KVM runtime

    """

    try:

      file_content = utils.ReadFile(self._InstanceKVMRuntime(instance_name))

    except EnvironmentError, err:

      raise errors.HypervisorError("Failed to load KVM runtime file: %s" % err)

    return file_content

  def _SaveKVMRuntime(self, instance, kvm_runtime):

    """Save an instance's KVM runtime

    """

    kvm_cmd, kvm_nics, hvparams = kvm_runtime

    serialized_nics = [nic.ToDict() for nic in kvm_nics]

    serialized_form = serializer.Dump((kvm_cmd, serialized_nics, hvparams))

    self._WriteKVMRuntime(instance.name, serialized_form)

  def _LoadKVMRuntime(self, instance, serialized_runtime=None):

    """Load an instance's KVM runtime

    """

    if not serialized_runtime:

      serialized_runtime = self._ReadKVMRuntime(instance.name)

    loaded_runtime = serializer.Load(serialized_runtime)

    kvm_cmd, serialized_nics, hvparams = loaded_runtime

    kvm_nics = [objects.NIC.FromDict(snic) for snic in serialized_nics]

    return (kvm_cmd, kvm_nics, hvparams)

  def _RunKVMCmd(self, name, kvm_cmd, tap_fds=None):

    """Run the KVM cmd and check for errors

    @type name: string

    @param name: instance name

    @type kvm_cmd: list of strings

    @param kvm_cmd: runcmd input for kvm

    @type tap_fds: list of int

    @param tap_fds: fds of tap devices opened by Ganeti

    """

    try:

      result = utils.RunCmd(kvm_cmd, noclose_fds=tap_fds)

    finally:

      for fd in tap_fds:

        utils_wrapper.CloseFdNoError(fd)

    if result.failed:

      raise errors.HypervisorError("Failed to start instance %s: %s (%s)" %

                                   (name, result.fail_reason, result.output))

    if not self._InstancePidAlive(name)[2]:

      raise errors.HypervisorError("Failed to start instance %s" % name)

  def _ExecuteKVMRuntime(self, instance, kvm_runtime, incoming=None):

    """Execute a KVM cmd, after completing it with some last minute data

    @type incoming: tuple of strings