Synnefo » snf-ganeti » ganeti-local

#

#

# Copyright (C) 2008 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 os

import os.path

import re

import tempfile

import time

import logging

import pwd

from cStringIO import StringIO

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

class KVMHypervisor(hv_base.BaseHypervisor):

  """KVM hypervisor interface"""

  _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

  _DIRS = [_ROOT_DIR, _PIDS_DIR, _UIDS_DIR, _CTRL_DIR, _CONF_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: (utils.IsValidIP(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_CDROM_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_USB_MOUSE:

      hv_base.ParamInSet(False, constants.HT_KVM_VALID_MOUSE_TYPES),

    constants.HV_MIGRATION_PORT: hv_base.NET_PORT_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),

    }

  _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

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

  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 _TryReadUidFile(cls, uid_file):

    """Try to read a uid file

    """

    if os.path.exists(uid_file):

      try:

        uid = int(utils.ReadFile(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.

    """

    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)

  def _WriteNetScript(self, instance, seq, nic):

    """Write a script to connect a net interface to the proper bridge.

    This can be used by any qemu-type hypervisor.

    @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

    @return: netscript file name

    @rtype: string

    """

    script = StringIO()

    script.write("#!/bin/sh\n")

    script.write("# this is autogenerated by Ganeti, please do not edit\n#\n")

    script.write("PATH=$PATH:/sbin:/usr/sbin\n")

    script.write("export INSTANCE=%s\n" % instance.name)

    script.write("export MAC=%s\n" % nic.mac)

    if nic.ip:

      script.write("export IP=%s\n" % nic.ip)

    script.write("export MODE=%s\n" % nic.nicparams[constants.NIC_MODE])

    if nic.nicparams[constants.NIC_LINK]:

      script.write("export LINK=%s\n" % nic.nicparams[constants.NIC_LINK])

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

      script.write("export BRIDGE=%s\n" % nic.nicparams[constants.NIC_LINK])

    script.write("export INTERFACE=$1\n")

    # TODO: make this configurable at ./configure time

    script.write("if [ -x '%s' ]; then\n" % self._KVM_NETWORK_SCRIPT)

    script.write("  # Execute the user-specific vif file\n")

    script.write("  %s\n" % self._KVM_NETWORK_SCRIPT)

    script.write("else\n")

    script.write("  ifconfig $INTERFACE 0.0.0.0 up\n")

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

      script.write("  # Connect the interface to the bridge\n")

      script.write("  brctl addif $BRIDGE $INTERFACE\n")

    elif nic.nicparams[constants.NIC_MODE] == constants.NIC_MODE_ROUTED:

      if not nic.ip:

        raise errors.HypervisorError("nic/%d is routed, but has no ip." % seq)

      script.write("  # Route traffic targeted at the IP to the interface\n")

      if nic.nicparams[constants.NIC_LINK]:

        script.write("  while ip rule del dev $INTERFACE; do :; done\n")

        script.write("  ip rule add dev $INTERFACE table $LINK\n")

        script.write("  ip route replace $IP table $LINK proto static"

                     " dev $INTERFACE\n")

      else:

        script.write("  ip route replace $IP proto static"

                     " dev $INTERFACE\n")

      interface_v4_conf = "/proc/sys/net/ipv4/conf/$INTERFACE"

      interface_v6_conf = "/proc/sys/net/ipv6/conf/$INTERFACE"

      script.write("  if [ -d %s ]; then\n" % interface_v4_conf)

      script.write("    echo 1 > %s/proxy_arp\n" % interface_v4_conf)

      script.write("    echo 1 > %s/forwarding\n" % interface_v4_conf)

      script.write("  fi\n")

      script.write("  if [ -d %s ]; then\n" % interface_v6_conf)

      script.write("    echo 1 > %s/proxy_ndp\n" % interface_v6_conf)

      script.write("    echo 1 > %s/forwarding\n" % interface_v6_conf)

      script.write("  fi\n")

    script.write("fi\n\n")

    # As much as we'd like to put this in our _ROOT_DIR, that will happen to be

    # mounted noexec sometimes, so we'll have to find another place.

    (tmpfd, tmpfile_name) = tempfile.mkstemp()

    tmpfile = os.fdopen(tmpfd, 'w')

    try:

      tmpfile.write(script.getvalue())

    finally:

      tmpfile.close()

    os.chmod(tmpfile_name, 0755)

    return tmpfile_name

  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_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'])

        boot_val = ',boot=on'

        # 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])

    iso_image = hvp[constants.HV_CDROM_IMAGE_PATH]

    if iso_image:

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

      if boot_cdrom:

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

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

      else:

        options = '%s,if=virtio' % options

      drive_val = 'file=%s%s' % (iso_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)])

    mouse_type = hvp[constants.HV_USB_MOUSE]

    if mouse_type:

      kvm_cmd.extend(['-usb'])

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

    vnc_bind_address = hvp[constants.HV_VNC_BIND_ADDRESS]

    if vnc_bind_address:

      if utils.IsValidIP(vnc_bind_address):

        if instance.network_port > constants.VNC_BASE_PORT:

          display = instance.network_port - constants.VNC_BASE_PORT

          if vnc_bind_address == '0.0.0.0':

            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])

      # Also add a tablet USB device to act as a mouse

      # This solves various mouse alignment issues

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

    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'])

    # 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):

    """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

    """

    result = utils.RunCmd(kvm_cmd)

    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

    @param incoming: (target_host_ip, port)

    """

    hvp = instance.hvparams

    name = instance.name

    self._CheckDown(name)

    temp_files = []

    kvm_cmd, kvm_nics, hvparams = kvm_runtime

    security_model = hvp[constants.HV_SECURITY_MODEL]

    if security_model == constants.HT_SM_USER:

      kvm_cmd.extend(["-runas", hvp[constants.HV_SECURITY_DOMAIN]])

    if not kvm_nics:

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

    else:

      nic_type = hvparams[constants.HV_NIC_TYPE]

      if nic_type == constants.HT_NIC_PARAVIRTUAL:

        nic_model = "model=virtio"

      else:

        nic_model = "model=%s" % nic_type

      for nic_seq, nic in enumerate(kvm_nics):

        nic_val = "nic,vlan=%s,macaddr=%s,%s" % (nic_seq, nic.mac, nic_model)

        script = self._WriteNetScript(instance, nic_seq, nic)

        kvm_cmd.extend(['-net', nic_val])

        kvm_cmd.extend(['-net', 'tap,vlan=%s,script=%s' % (nic_seq, script)])

        temp_files.append(script)

    if incoming:

      target, port = incoming

      kvm_cmd.extend(['-incoming', 'tcp:%s:%s' % (target, port)])

    vnc_pwd_file = hvp[constants.HV_VNC_PASSWORD_FILE]

    vnc_pwd = None

    if vnc_pwd_file:

      try:

        vnc_pwd = utils.ReadFile(vnc_pwd_file)

      except EnvironmentError, err:

        raise errors.HypervisorError("Failed to open VNC password file %s: %s"

                                     % (vnc_pwd_file, err))

    if security_model == constants.HT_SM_POOL:

      ss = ssconf.SimpleStore()

      uid_pool = uidpool.ParseUidPool(ss.GetUidPool(), separator="\n")

      all_uids = set(uidpool.ExpandUidPool(uid_pool))

      uid = uidpool.RequestUnusedUid(all_uids)

      try:

        username = pwd.getpwuid(uid.GetUid()).pw_name

        kvm_cmd.extend(["-runas", username])

        self._RunKVMCmd(name, kvm_cmd)

      except:

        uidpool.ReleaseUid(uid)

        raise

      else:

        uid.Unlock()

        utils.WriteFile(self._InstanceUidFile(name), data=str(uid))

    else:

      self._RunKVMCmd(name, kvm_cmd)

    if vnc_pwd:

      change_cmd = 'change vnc password %s' % vnc_pwd

      self._CallMonitorCommand(instance.name, change_cmd)

    for filename in temp_files:

      utils.RemoveFile(filename)

  def StartInstance(self, instance, block_devices):

    """Start an instance.

    """

    self._CheckDown(instance.name)

    kvm_runtime = self._GenerateKVMRuntime(instance, block_devices)

    self._SaveKVMRuntime(instance, kvm_runtime)

    self._ExecuteKVMRuntime(instance, kvm_runtime)

  def _CallMonitorCommand(self, instance_name, command):

    """Invoke a command on the instance monitor.

    """

    socat = ("echo %s | %s STDIO UNIX-CONNECT:%s" %

             (utils.ShellQuote(command),

              constants.SOCAT_PATH,

              utils.ShellQuote(self._InstanceMonitor(instance_name))))

    result = utils.RunCmd(socat)

    if result.failed:

      msg = ("Failed to send command '%s' to instance %s."

             " output: %s, error: %s, fail_reason: %s" %

             (command, instance_name,

              result.stdout, result.stderr, result.fail_reason))

      raise errors.HypervisorError(msg)

    return result

  def StopInstance(self, instance, force=False, retry=False, name=None):

    """Stop an instance.

    """

    if name is not None and not force:

      raise errors.HypervisorError("Cannot shutdown cleanly by name only")

    if name is None:

      name = instance.name

      acpi = instance.hvparams[constants.HV_ACPI]

    else:

      acpi = False

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

    if pid > 0 and alive:

      if force or not acpi:

        utils.KillProcess(pid)

      else:

        self._CallMonitorCommand(name, 'system_powerdown')

  def CleanupInstance(self, instance_name):

    """Cleanup after a stopped instance

    """

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

    if pid > 0 and alive:

      raise errors.HypervisorError("Cannot cleanup a live instance")

    self._RemoveInstanceRuntimeFiles(pidfile, instance_name)

  def RebootInstance(self, instance):

    """Reboot an instance.

    """

    # For some reason if we do a 'send-key ctrl-alt-delete' to the control

    # socket the instance will stop, but now power up again. So we'll resort

    # to shutdown and restart.

    _, _, alive = self._InstancePidAlive(instance.name)

    if not alive:

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

                                   " not running" % instance.name)

    # StopInstance will delete the saved KVM runtime so:

    # ...first load it...

    kvm_runtime = self._LoadKVMRuntime(instance)

    # ...now we can safely call StopInstance...

    if not self.StopInstance(instance):

      self.StopInstance(instance, force=True)

    # ...and finally we can save it again, and execute it...

    self._SaveKVMRuntime(instance, kvm_runtime)

    self._ExecuteKVMRuntime(instance, kvm_runtime)

  def MigrationInfo(self, instance):

    """Get instance information to perform a migration.

    @type instance: L{objects.Instance}

    @param instance: instance to be migrated

    @rtype: string

    @return: content of the KVM runtime file

    """

    return self._ReadKVMRuntime(instance.name)

  def AcceptInstance(self, instance, info, target):

    """Prepare to accept an instance.

    @type instance: L{objects.Instance}

    @param instance: instance to be accepted

    @type info: string

    @param info: content of the KVM runtime file on the source node

    @type target: string

    @param target: target host (usually ip), on this node

    """

    kvm_runtime = self._LoadKVMRuntime(instance, serialized_runtime=info)

    incoming_address = (target, instance.hvparams[constants.HV_MIGRATION_PORT])

    self._ExecuteKVMRuntime(instance, kvm_runtime, incoming=incoming_address)

  def FinalizeMigration(self, instance, info, success):

    """Finalize an instance migration.

    Stop the incoming mode KVM.