diff --git a/Makefile.am b/Makefile.am
index fbb8f8745fa9316f4f320539e7fd0b1d62979458..78b5c4d15ad218d6fdbca208cab36aec2ddb7750 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -234,6 +234,7 @@ dist_tools_SCRIPTS = \
 	tools/burnin \
 	tools/cfgshell \
 	tools/cfgupgrade \
+	tools/cfgupgrade12 \
 	tools/cluster-merge \
 	tools/lvmstrap \
 	tools/sanitize-config
diff --git a/doc/admin.rst b/doc/admin.rst
index 8ac2b59c5562ab3adb314669524acaea86d9eed8..778c2d74558c2df2e0537e71668a83c5b692f366 100644
--- a/doc/admin.rst
+++ b/doc/admin.rst
@@ -1304,6 +1304,9 @@ Ganeti versions. Point-releases are usually transparent for the admin.
 More information about the upgrade procedure is listed on the wiki at
 http://code.google.com/p/ganeti/wiki/UpgradeNotes.
 
+There is also a script designed to upgrade from Ganeti 1.2 to 2.0,
+called ``cfgupgrade12``.
+
 cfgshell
 ++++++++
 
diff --git a/tools/cfgupgrade12 b/tools/cfgupgrade12
new file mode 100755
index 0000000000000000000000000000000000000000..2ebccce3e24ed04b08b2d02f1ce941c0bd7898fc
--- /dev/null
+++ b/tools/cfgupgrade12
@@ -0,0 +1,418 @@
+#!/usr/bin/python
+#
+
+# Copyright (C) 2007, 2008, 2009 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.
+
+# pylint: disable-msg=C0103,E1103
+
+# C0103: invalid name NoDefault
+# E1103: Instance of 'foor' has no 'bar' member (but some types could
+# not be inferred)
+
+
+"""Tool to upgrade the configuration file.
+
+This code handles only the types supported by simplejson. As an
+example, 'set' is a 'list'.
+
+@note: this has lots of duplicate content with C{cfgupgrade}. Ideally, it
+should be merged.
+
+"""
+
+
+import os
+import os.path
+import sys
+import optparse
+import logging
+import errno
+
+from ganeti import constants
+from ganeti import serializer
+from ganeti import utils
+from ganeti import cli
+from ganeti import bootstrap
+
+
+options = None
+args = None
+
+# Unique object to identify calls without default value
+NoDefault = object()
+
+# Dictionary with instance old keys, and new hypervisor keys
+INST_HV_CHG = {
+  'hvm_pae': constants.HV_PAE,
+  'vnc_bind_address': constants.HV_VNC_BIND_ADDRESS,
+  'initrd_path': constants.HV_INITRD_PATH,
+  'hvm_nic_type': constants.HV_NIC_TYPE,
+  'kernel_path': constants.HV_KERNEL_PATH,
+  'hvm_acpi': constants.HV_ACPI,
+  'hvm_cdrom_image_path': constants.HV_CDROM_IMAGE_PATH,
+  'hvm_boot_order': constants.HV_BOOT_ORDER,
+  'hvm_disk_type': constants.HV_DISK_TYPE,
+  }
+
+# Instance beparams changes
+INST_BE_CHG = {
+  'vcpus': constants.BE_VCPUS,
+  'memory': constants.BE_MEMORY,
+  'auto_balance': constants.BE_AUTO_BALANCE,
+  }
+
+# Field names
+F_SERIAL = 'serial_no'
+
+
+class Error(Exception):
+  """Generic exception"""
+  pass
+
+
+def SsconfName(key):
+  """Returns the file name of an (old) ssconf key.
+
+  """
+  return "%s/ssconf_%s" % (options.data_dir, key)
+
+
+def ReadFile(file_name, default=NoDefault):
+  """Reads a file.
+
+  """
+  logging.debug("Reading %s", file_name)
+  try:
+    fh = open(file_name, 'r')
+  except IOError, err:
+    if default is not NoDefault and err.errno == errno.ENOENT:
+      return default
+    raise
+
+  try:
+    return fh.read()
+  finally:
+    fh.close()
+
+
+def WriteFile(file_name, data):
+  """Writes a configuration file.
+
+  """
+  logging.debug("Writing %s", file_name)
+  utils.WriteFile(file_name=file_name, data=data, mode=0600,
+                  dry_run=options.dry_run, backup=True)
+
+
+def GenerateSecret(all_secrets):
+  """Generate an unique DRBD secret.
+
+  This is a copy from ConfigWriter.
+
+  """
+  retries = 64
+  while retries > 0:
+    secret = utils.GenerateSecret()
+    if secret not in all_secrets:
+      break
+    retries -= 1
+  else:
+    raise Error("Can't generate unique DRBD secret")
+  return secret
+
+
+def SetupLogging():
+  """Configures the logging module.
+
+  """
+  formatter = logging.Formatter("%(asctime)s: %(message)s")
+
+  stderr_handler = logging.StreamHandler()
+  stderr_handler.setFormatter(formatter)
+  if options.debug:
+    stderr_handler.setLevel(logging.NOTSET)
+  elif options.verbose:
+    stderr_handler.setLevel(logging.INFO)
+  else:
+    stderr_handler.setLevel(logging.CRITICAL)
+
+  root_logger = logging.getLogger("")
+  root_logger.setLevel(logging.NOTSET)
+  root_logger.addHandler(stderr_handler)
+
+
+def Cluster12To20(cluster):
+  """Upgrades the cluster object from 1.2 to 2.0.
+
+  """
+  logging.info("Upgrading the cluster object")
+  # Upgrade the configuration version
+  if 'config_version' in cluster:
+    del cluster['config_version']
+
+  # Add old ssconf keys back to config
+  logging.info(" - importing ssconf keys")
+  for key in ('master_node', 'master_ip', 'master_netdev', 'cluster_name'):
+    if key not in cluster:
+      cluster[key] = ReadFile(SsconfName(key)).strip()
+
+  if 'default_hypervisor' not in cluster:
+    old_hyp = ReadFile(SsconfName('hypervisor')).strip()
+    if old_hyp == "xen-3.0":
+      hyp = "xen-pvm"
+    elif old_hyp == "xen-hvm-3.1":
+      hyp = "xen-hvm"
+    elif old_hyp == "fake":
+      hyp = "fake"
+    else:
+      raise Error("Unknown old hypervisor name '%s'" % old_hyp)
+
+    logging.info("Setting the default and enabled hypervisor")
+    cluster['default_hypervisor'] = hyp
+    cluster['enabled_hypervisors'] = [hyp]
+
+  # hv/be params
+  if 'hvparams' not in cluster:
+    logging.info(" - adding hvparams")
+    cluster['hvparams'] = constants.HVC_DEFAULTS
+  if 'beparams' not in cluster:
+    logging.info(" - adding beparams")
+    cluster['beparams'] = {constants.PP_DEFAULT: constants.BEC_DEFAULTS}
+
+  # file storage
+  if 'file_storage_dir' not in cluster:
+    cluster['file_storage_dir'] = constants.DEFAULT_FILE_STORAGE_DIR
+
+  # candidate pool size
+  if 'candidate_pool_size' not in cluster:
+    cluster['candidate_pool_size'] = constants.MASTER_POOL_SIZE_DEFAULT
+
+
+def Node12To20(node):
+  """Upgrades a node from 1.2 to 2.0.
+
+  """
+  logging.info("Upgrading node %s", node['name'])
+  if F_SERIAL not in node:
+    node[F_SERIAL] = 1
+  if 'master_candidate' not in node:
+    node['master_candidate'] = True
+  for key in 'offline', 'drained':
+    if key not in node:
+      node[key] = False
+
+
+def Instance12To20(drbd_minors, secrets, hypervisor, instance):
+  """Upgrades an instance from 1.2 to 2.0.
+
+  """
+  if F_SERIAL not in instance:
+    instance[F_SERIAL] = 1
+
+  if 'hypervisor' not in instance:
+    instance['hypervisor'] = hypervisor
+
+  # hvparams changes
+  if 'hvparams' not in instance:
+    instance['hvparams'] = hvp = {}
+  for old, new in INST_HV_CHG.items():
+    if old in instance:
+      if (instance[old] is not None and
+          instance[old] != constants.VALUE_DEFAULT and # no longer valid in 2.0
+          new in constants.HVC_DEFAULTS[hypervisor]):
+        hvp[new] = instance[old]
+      del instance[old]
+
+  # beparams changes
+  if 'beparams' not in instance:
+    instance['beparams'] = bep = {}
+  for old, new in INST_BE_CHG.items():
+    if old in instance:
+      if instance[old] is not None:
+        bep[new] = instance[old]
+      del instance[old]
+
+  # disk changes
+  for disk in instance['disks']:
+    Disk12To20(drbd_minors, secrets, disk)
+
+  # other instance changes
+  if 'status' in instance:
+    instance['admin_up'] = instance['status'] == 'up'
+    del instance['status']
+
+
+def Disk12To20(drbd_minors, secrets, disk):
+  """Upgrades a disk from 1.2 to 2.0.
+
+  """
+  if 'mode' not in disk:
+    disk['mode'] = constants.DISK_RDWR
+  if disk['dev_type'] == constants.LD_DRBD8:
+    old_lid = disk['logical_id']
+    for node in old_lid[:2]:
+      if node not in drbd_minors:
+        raise Error("Can't find node '%s' while upgrading disk" % node)
+      drbd_minors[node] += 1
+      minor = drbd_minors[node]
+      old_lid.append(minor)
+    old_lid.append(GenerateSecret(secrets))
+    del disk['physical_id']
+  if disk['children']:
+    for child in disk['children']:
+      Disk12To20(drbd_minors, secrets, child)
+
+
+def main():
+  """Main program.
+
+  """
+  # pylint: disable-msg=W0603
+  global options, args
+
+  program = os.path.basename(sys.argv[0])
+
+  # Option parsing
+  parser = optparse.OptionParser(usage="%prog [--debug|--verbose] [--force]")
+  parser.add_option('--dry-run', dest='dry_run',
+                    action="store_true",
+                    help="Try to do the conversion, but don't write"
+                         " output file")
+  parser.add_option(cli.FORCE_OPT)
+  parser.add_option(cli.DEBUG_OPT)
+  parser.add_option(cli.VERBOSE_OPT)
+  parser.add_option('--path', help="Convert configuration in this"
+                    " directory instead of '%s'" % constants.DATA_DIR,
+                    default=constants.DATA_DIR, dest="data_dir")
+  (options, args) = parser.parse_args()
+
+  # We need to keep filenames locally because they might be renamed between
+  # versions.
+  options.CONFIG_DATA_PATH = options.data_dir + "/config.data"
+  options.SERVER_PEM_PATH = options.data_dir + "/server.pem"
+  options.KNOWN_HOSTS_PATH = options.data_dir + "/known_hosts"
+  options.RAPI_CERT_FILE = options.data_dir + "/rapi.pem"
+
+  SetupLogging()
+
+  # Option checking
+  if args:
+    raise Error("No arguments expected")
+
+  if not options.force:
+    usertext = ("%s MUST be run on the master node. Is this the master"
+                " node and are ALL instances down?" % program)
+    if not cli.AskUser(usertext):
+      sys.exit(1)
+
+  # Check whether it's a Ganeti configuration directory
+  if not (os.path.isfile(options.CONFIG_DATA_PATH) and
+          os.path.isfile(options.SERVER_PEM_PATH) or
+          os.path.isfile(options.KNOWN_HOSTS_PATH)):
+    raise Error(("%s does not seem to be a known Ganeti configuration"
+                 " directory") % options.data_dir)
+
+  config_version = ReadFile(SsconfName('config_version'), "1.2").strip()
+  logging.info("Found configuration version %s", config_version)
+
+  config_data = serializer.LoadJson(ReadFile(options.CONFIG_DATA_PATH))
+
+  # Ganeti 1.2?
+  if config_version == "1.2":
+    logging.info("Found a Ganeti 1.2 configuration")
+
+    cluster = config_data["cluster"]
+
+    old_config_version = cluster.get("config_version", None)
+    logging.info("Found old configuration version %s", old_config_version)
+    if old_config_version not in (3, ):
+      raise Error("Unsupported configuration version: %s" %
+                  old_config_version)
+    if 'version' not in config_data:
+      config_data['version'] = constants.BuildVersion(2, 0, 0)
+    if F_SERIAL not in config_data:
+      config_data[F_SERIAL] = 1
+
+    # Make sure no instance uses remote_raid1 anymore
+    remote_raid1_instances = []
+    for instance in config_data["instances"].values():
+      if instance["disk_template"] == "remote_raid1":
+        remote_raid1_instances.append(instance["name"])
+    if remote_raid1_instances:
+      for name in remote_raid1_instances:
+        logging.error("Instance %s still using remote_raid1 disk template",
+                      name)
+      raise Error("Unable to convert configuration as long as there are"
+                  " instances using remote_raid1 disk template")
+
+    # Build content of new known_hosts file
+    cluster_name = ReadFile(SsconfName('cluster_name')).rstrip()
+    cluster_key = cluster['rsahostkeypub']
+    known_hosts = "%s ssh-rsa %s\n" % (cluster_name, cluster_key)
+
+    Cluster12To20(cluster)
+
+    # Add node attributes
+    logging.info("Upgrading nodes")
+    # stable-sort the names to have repeatable runs
+    for node_name in utils.NiceSort(config_data['nodes'].keys()):
+      Node12To20(config_data['nodes'][node_name])
+
+    # Instance changes
+    logging.info("Upgrading instances")
+    drbd_minors = dict.fromkeys(config_data['nodes'], 0)
+    secrets = set()
+    # stable-sort the names to have repeatable runs
+    for instance_name in utils.NiceSort(config_data['instances'].keys()):
+      Instance12To20(drbd_minors, secrets, cluster['default_hypervisor'],
+                     config_data['instances'][instance_name])
+
+  else:
+    logging.info("Found a Ganeti 2.0 configuration")
+
+    if "config_version" in config_data["cluster"]:
+      raise Error("Inconsistent configuration: found config_data in"
+                  " configuration file")
+
+    known_hosts = None
+
+  try:
+    logging.info("Writing configuration file")
+    WriteFile(options.CONFIG_DATA_PATH, serializer.DumpJson(config_data))
+
+    if known_hosts is not None:
+      logging.info("Writing SSH known_hosts file (%s)", known_hosts.strip())
+      WriteFile(options.KNOWN_HOSTS_PATH, known_hosts)
+
+    if not options.dry_run:
+      if not os.path.exists(options.RAPI_CERT_FILE):
+        logging.debug("Writing RAPI certificate to %s", options.RAPI_CERT_FILE)
+        bootstrap.GenerateSelfSignedSslCert(options.RAPI_CERT_FILE)
+
+  except:
+    logging.critical("Writing configuration failed. It is probably in an"
+                     " inconsistent state and needs manual intervention.")
+    raise
+
+  logging.info("Configuration file updated.")
+
+
+if __name__ == "__main__":
+  main()
+
+# vim: set foldmethod=marker :