Create directories in the Python package for distro-specific logic. (#535)

- Finish creating distro directories.
- Import correct module based on distro type.
- Refactor 'network_setup' to use these new directories.

26 files changed, 671 insertions, 177 deletions

diff --git a/google_compute_engine/compat.py b/google_compute_engine/compat.py
index 00d9d45..bafb1f7 100644
--- a/google_compute_engine/compat.py
+++ b/google_compute_engine/compat.py
@@ -16,9 +16,32 @@
 """A module for resolving compatibility issues between Python 2 and Python 3."""
 
 import logging
+import platform
 import subprocess
 import sys
 
+# Set distro-specific utils.
+distribution = platform.linux_distribution()
+distro_name = distribution[0].lower()
+distro_version = distribution[1].split('.')[0]
+distro_utils = None
+
+if 'centos' in distro_name and distro_version == '6':
+  import google_compute_engine.distro.el_6.utils as distro_utils
+elif 'centos' in distro_name and distro_version == '7':
+  import google_compute_engine.distro.el_7.utils as distro_utils
+elif 'red hat enterprise linux' in distro_name and distro_version == '6':
+  import google_compute_engine.distro.el_6.utils as distro_utils
+elif 'red hat enterprise linux' in distro_name and distro_version == '7':
+  import google_compute_engine.distro.el_7.utils as distro_utils
+elif 'debian' in distro_name and distro_version == '8':
+  import google_compute_engine.distro.debian_8.utils as distro_utils
+elif 'debian' in distro_name and distro_version == '9':
+  import google_compute_engine.distro.debian_9.utils as distro_utils
+else:
+  # Default to Debian 9.
+  import google_compute_engine.distro.debian_9.utils as distro_utils
+
 RETRY_LIMIT = 3
 TIMEOUT = 10
 
diff --git a/google_compute_engine/distro/__init__.py b/google_compute_engine/distro/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/__init__.py
diff --git a/google_compute_engine/distro/debian_8/__init__.py b/google_compute_engine/distro/debian_8/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/debian_8/__init__.py
diff --git a/google_compute_engine/distro/debian_8/tests/__init__.py b/google_compute_engine/distro/debian_8/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/debian_8/tests/__init__.py
diff --git a/google_compute_engine/distro/debian_8/tests/utils_test.py b/google_compute_engine/distro/debian_8/tests/utils_test.py
new file mode 100644
index 0000000..0bb6d39
--- /dev/null
+++ b/google_compute_engine/distro/debian_8/tests/utils_test.py
@@ -0,0 +1,37 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittest for utils.py module."""
+
+from google_compute_engine.distro.debian_8 import utils
+from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import unittest
+
+
+class UtilsTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mock_logger = mock.Mock()
+    self.mock_setup = mock.create_autospec(utils.Utils)
+
+  @mock.patch('google_compute_engine.distro.helpers.CallDhclient')
+  def testEnableNetworkInterfaces(self, mock_call):
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_call, 'call')
+
+    utils.Utils.EnableNetworkInterfaces(
+        self.mock_setup, ['A', 'B'], self.mock_logger)
+    expected_calls = [mock.call.call(['A', 'B'], mock.ANY)]
+    self.assertEqual(mocks.mock_calls, expected_calls)
diff --git a/google_compute_engine/distro/debian_8/utils.py b/google_compute_engine/distro/debian_8/utils.py
new file mode 100644
index 0000000..b4aade5
--- /dev/null
+++ b/google_compute_engine/distro/debian_8/utils.py
@@ -0,0 +1,34 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities that are distro specific for use on Debian 8."""
+
+from google_compute_engine.distro import helpers
+from google_compute_engine.distro import utils
+
+
+class Utils(utils.Utils):
+  """Utilities used by Linux guest services on Debian 8."""
+
+  def EnableNetworkInterfaces(
+      self, interfaces, logger, dhclient_script=None):
+    """Enable the list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names to enable.
+      logger: logger object, used to write to SysLog and serial port.
+      dhclient_script: string, the path to a dhclient script used by dhclient.
+    """
+    helpers.CallDhclient(interfaces, logger)
diff --git a/google_compute_engine/distro/debian_9/__init__.py b/google_compute_engine/distro/debian_9/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/debian_9/__init__.py
diff --git a/google_compute_engine/distro/debian_9/tests/__init__.py b/google_compute_engine/distro/debian_9/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/debian_9/tests/__init__.py
diff --git a/google_compute_engine/distro/debian_9/tests/utils_test.py b/google_compute_engine/distro/debian_9/tests/utils_test.py
new file mode 100644
index 0000000..633ba9b
--- /dev/null
+++ b/google_compute_engine/distro/debian_9/tests/utils_test.py
@@ -0,0 +1,37 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittest for utils.py module."""
+
+from google_compute_engine.distro.debian_9 import utils
+from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import unittest
+
+
+class UtilsTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mock_logger = mock.Mock()
+    self.mock_setup = mock.create_autospec(utils.Utils)
+
+  @mock.patch('google_compute_engine.distro.helpers.CallDhclient')
+  def testEnableNetworkInterfaces(self, mock_call):
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_call, 'call')
+
+    utils.Utils.EnableNetworkInterfaces(
+        self.mock_setup, ['A', 'B'], self.mock_logger)
+    expected_calls = [mock.call.call(['A', 'B'], mock.ANY)]
+    self.assertEqual(mocks.mock_calls, expected_calls)
diff --git a/google_compute_engine/distro/debian_9/utils.py b/google_compute_engine/distro/debian_9/utils.py
new file mode 100644
index 0000000..f235723
--- /dev/null
+++ b/google_compute_engine/distro/debian_9/utils.py
@@ -0,0 +1,34 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities that are distro specific for use on Debian 9."""
+
+from google_compute_engine.distro import helpers
+from google_compute_engine.distro import utils
+
+
+class Utils(utils.Utils):
+  """Utilities used by Linux guest services on Debian 9."""
+
+  def EnableNetworkInterfaces(
+      self, interfaces, logger, dhclient_script=None):
+    """Enable the list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names to enable.
+      logger: logger object, used to write to SysLog and serial port.
+      dhclient_script: string, the path to a dhclient script used by dhclient.
+    """
+    helpers.CallDhclient(interfaces, logger)
diff --git a/google_compute_engine/distro/el_6/__init__.py b/google_compute_engine/distro/el_6/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/el_6/__init__.py
diff --git a/google_compute_engine/distro/el_6/tests/__init__.py b/google_compute_engine/distro/el_6/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/el_6/tests/__init__.py
diff --git a/google_compute_engine/distro/el_6/tests/utils_test.py b/google_compute_engine/distro/el_6/tests/utils_test.py
new file mode 100644
index 0000000..363046c
--- /dev/null
+++ b/google_compute_engine/distro/el_6/tests/utils_test.py
@@ -0,0 +1,43 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittest for utils.py module."""
+
+from google_compute_engine.distro.el_6 import utils
+from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import unittest
+
+
+class UtilsTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mock_logger = mock.Mock()
+    self.mock_setup = mock.create_autospec(utils.Utils)
+
+  def tearDown(self):
+    pass
+
+  @mock.patch('google_compute_engine.distro.helpers.CallDhclient')
+  def testEnableNetworkInterfaces(self, mock_call):
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_call, 'call')
+
+    utils.Utils.EnableNetworkInterfaces(
+        self.mock_setup, ['A', 'B'], self.mock_logger,
+        dhclient_script='test_script')
+    expected_calls = [
+        mock.call.call(['A', 'B'], mock.ANY, dhclient_script='test_script'),
+    ]
+    self.assertEqual(mocks.mock_calls, expected_calls)
diff --git a/google_compute_engine/distro/el_6/utils.py b/google_compute_engine/distro/el_6/utils.py
new file mode 100644
index 0000000..fc70541
--- /dev/null
+++ b/google_compute_engine/distro/el_6/utils.py
@@ -0,0 +1,34 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities that are distro specific for use on EL 6."""
+
+from google_compute_engine.distro import helpers
+from google_compute_engine.distro import utils
+
+
+class Utils(utils.Utils):
+  """Utilities used by Linux guest services on Debian 8."""
+
+  def EnableNetworkInterfaces(
+      self, interfaces, logger, dhclient_script=None):
+    """Enable the list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names to enable.
+      logger: logger object, used to write to SysLog and serial port.
+      dhclient_script: string, the path to a dhclient script used by dhclient.
+    """
+    helpers.CallDhclient(interfaces, logger, dhclient_script=dhclient_script)
diff --git a/google_compute_engine/distro/el_7/__init__.py b/google_compute_engine/distro/el_7/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/el_7/__init__.py
diff --git a/google_compute_engine/distro/el_7/tests/__init__.py b/google_compute_engine/distro/el_7/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/google_compute_engine/distro/el_7/tests/__init__.py
diff --git a/google_compute_engine/distro/el_7/tests/utils_test.py b/google_compute_engine/distro/el_7/tests/utils_test.py
new file mode 100644
index 0000000..95ef298
--- /dev/null
+++ b/google_compute_engine/distro/el_7/tests/utils_test.py
@@ -0,0 +1,122 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittest for utils.py module."""
+
+import os
+import shutil
+import tempfile
+
+from google_compute_engine.distro.el_7 import utils
+from google_compute_engine.test_compat import builtin
+from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import unittest
+
+
+class UtilsTest(unittest.TestCase):
+
+  def setUp(self):
+    # Create a temporary directory.
+    self.test_dir = tempfile.mkdtemp()
+    self.mock_logger = mock.Mock()
+    self.mock_setup = mock.create_autospec(utils.Utils)
+    self.mock_setup.network_path = '/etc/sysconfig/network-scripts'
+
+  def tearDown(self):
+    # Remove the directory after the test.
+    shutil.rmtree(self.test_dir)
+
+  def testModifyInterface(self):
+    config_file = os.path.join(self.test_dir, 'config.cfg')
+    config_content = [
+        '# File comment.\n',
+        'A="apple"\n',
+        'B=banana\n',
+        'B=banana\n',
+    ]
+    with open(config_file, 'w') as config:
+      for line in config_content:
+        config.write(line)
+
+    # Write a value for an existing config without overriding it.
+    utils.Utils._ModifyInterface(
+        self.mock_setup, config_file, 'A', 'aardvark', replace=False)
+    self.assertEquals(open(config_file).readlines(), config_content)
+    # Write a value for a config that is not already set.
+    utils.Utils._ModifyInterface(
+        self.mock_setup, config_file, 'C', 'none', replace=False)
+    config_content.append('C=none\n')
+    self.assertEquals(open(config_file).readlines(), config_content)
+    # Write a value for an existing config with replacement.
+    utils.Utils._ModifyInterface(
+        self.mock_setup, config_file, 'A', 'aardvark', replace=True)
+    config_content[1] = 'A=aardvark\n'
+    self.assertEquals(open(config_file).readlines(), config_content)
+    # Write a value for an existing config with multiple occurrences.
+    utils.Utils._ModifyInterface(
+        self.mock_setup, config_file, 'B', '"banana"', replace=True)
+    config_content[2] = config_content[3] = 'B="banana"\n'
+    self.assertEquals(open(config_file).readlines(), config_content)
+
+  @mock.patch('google_compute_engine.distro.el_7.utils.os.path.exists')
+  def testDisableNetworkManager(self, mock_exists):
+    mock_open = mock.mock_open()
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_exists, 'exists')
+    mocks.attach_mock(mock_open, 'open')
+    mocks.attach_mock(self.mock_logger, 'logger')
+    mocks.attach_mock(self.mock_setup._ModifyInterface, 'modify')
+    mock_exists.side_effect = [True, False]
+
+    with mock.patch('%s.open' % builtin, mock_open, create=False):
+      utils.Utils._DisableNetworkManager(
+          self.mock_setup, ['eth0', 'eth1'], self.mock_logger)
+      expected_calls = [
+          mock.call.exists('/etc/sysconfig/network-scripts/ifcfg-eth0'),
+          mock.call.modify(mock.ANY, 'DEVICE', 'eth0', replace=False),
+          mock.call.modify(mock.ANY, 'NM_CONTROLLED', 'no', replace=True),
+          mock.call.exists('/etc/sysconfig/network-scripts/ifcfg-eth1'),
+          mock.call.open('/etc/sysconfig/network-scripts/ifcfg-eth1', 'w'),
+          mock.call.open().__enter__(),
+          mock.call.open().write(mock.ANY),
+          mock.call.open().__exit__(None, None, None),
+          mock.call.logger.info(mock.ANY, 'eth1'),
+      ]
+      self.assertEqual(mocks.mock_calls, expected_calls)
+
+  @mock.patch('google_compute_engine.distro.el_7.utils.os.path.exists')
+  @mock.patch('google_compute_engine.distro.helpers.CallDhclient')
+  def testEnableNetworkInterfaces(self, mock_call, mock_exists):
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_exists, 'exists')
+    mocks.attach_mock(self.mock_logger, 'logger')
+    mocks.attach_mock(self.mock_setup._DisableNetworkManager, 'disable')
+    mocks.attach_mock(mock_call, 'call_dhclient')
+    mock_exists.side_effect = [True, False]
+
+    # Enable interfaces with network manager enabled.
+    utils.Utils.EnableNetworkInterfaces(
+        self.mock_setup, ['A', 'B'], self.mock_logger)
+    # Enable interfaces with network manager is not present.
+    utils.Utils.EnableNetworkInterfaces(
+        self.mock_setup, ['C', 'D'], self.mock_logger)
+    expected_calls = [
+        mock.call.exists('/etc/sysconfig/network-scripts'),
+        mock.call.disable(['A', 'B'], mock.ANY),
+        mock.call.call_dhclient(['A', 'B'], mock.ANY),
+        mock.call.exists('/etc/sysconfig/network-scripts'),
+        mock.call.call_dhclient(['C', 'D'], mock.ANY),
+    ]
+    self.assertEqual(mocks.mock_calls, expected_calls)
diff --git a/google_compute_engine/distro/el_7/utils.py b/google_compute_engine/distro/el_7/utils.py
new file mode 100644
index 0000000..a17cf56
--- /dev/null
+++ b/google_compute_engine/distro/el_7/utils.py
@@ -0,0 +1,91 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities that are distro specific for use on EL 7."""
+
+import fileinput
+import os
+import re
+
+from google_compute_engine import constants
+from google_compute_engine.distro import helpers
+from google_compute_engine.distro import utils
+
+
+class Utils(utils.Utils):
+  """Utilities used by Linux guest services on EL 7."""
+
+  network_path = constants.LOCALBASE + '/etc/sysconfig/network-scripts'
+
+  def EnableNetworkInterfaces(
+      self, interfaces, logger, dhclient_script=None):
+    """Enable the list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names to enable.
+      logger: logger object, used to write to SysLog and serial port.
+      dhclient_script: string, the path to a dhclient script used by dhclient.
+    """
+    # Should always exist in EL 7.
+    if os.path.exists(self.network_path):
+      self._DisableNetworkManager(interfaces, logger)
+    helpers.CallDhclient(interfaces, logger)
+
+  def _DisableNetworkManager(self, interfaces, logger):
+    """Disable network manager management on a list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names enable.
+      logger: logger object, used to write to SysLog and serial port.
+    """
+    for interface in interfaces:
+      interface_config = os.path.join(self.network_path, 'ifcfg-%s' % interface)
+      if os.path.exists(interface_config):
+        self._ModifyInterface(
+            interface_config, 'DEVICE', interface, replace=False)
+        self._ModifyInterface(
+            interface_config, 'NM_CONTROLLED', 'no', replace=True)
+      else:
+        with open(interface_config, 'w') as interface_file:
+          interface_content = [
+              '# Added by Google.',
+              'BOOTPROTO=none',
+              'DEFROUTE=no',
+              'DEVICE=%s' % interface,
+              'IPV6INIT=no',
+              'NM_CONTROLLED=no',
+              'NOZEROCONF=yes',
+              '',
+          ]
+          interface_file.write('\n'.join(interface_content))
+        logger.info('Created config file for interface %s.', interface)
+
+  def _ModifyInterface(
+      self, interface_config, config_key, config_value, replace=False):
+    """Write a value to a config file if not already present.
+
+    Args:
+      interface_config: string, the path to a config file.
+      config_key: string, the configuration key to set.
+      config_value: string, the value to set for the configuration key.
+      replace: bool, replace the configuration option if already present.
+    """
+    config_entry = '%s=%s' % (config_key, config_value)
+    if not open(interface_config).read().count(config_key):
+      with open(interface_config, 'a') as config:
+        config.write('%s\n' % config_entry)
+    elif replace:
+      for line in fileinput.input(interface_config, inplace=True):
+        print(re.sub(r'%s=.*' % config_key, config_entry, line.rstrip()))
diff --git a/google_compute_engine/distro/helpers.py b/google_compute_engine/distro/helpers.py
new file mode 100644
index 0000000..7e7272c
--- /dev/null
+++ b/google_compute_engine/distro/helpers.py
@@ -0,0 +1,42 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Distro helpers."""
+
+import os
+import subprocess
+
+
+def CallDhclient(
+    interfaces, logger, dhclient_script=None):
+  """Configure the network interfaces using dhclient.
+
+  Args:
+    interfaces: list of string, the output device names to enable.
+    logger: logger object, used to write to SysLog and serial port.
+    dhclient_script: string, the path to a dhclient script used by dhclient.
+  """
+  logger.info('Enabling the Ethernet interfaces %s.', interfaces)
+
+  dhclient_command = ['dhclient']
+
+  if dhclient_script and os.path.exists(dhclient_script):
+    dhclient_command += ['-sf', dhclient_script]
+
+  try:
+    subprocess.check_call(dhclient_command + ['-x'] + interfaces)
+    subprocess.check_call(dhclient_command + interfaces)
+  except subprocess.CalledProcessError:
+    logger.warning('Could not enable interfaces %s.', interfaces)
diff --git a/google_compute_engine/distro/tests/helpers_test.py b/google_compute_engine/distro/tests/helpers_test.py
new file mode 100644
index 0000000..75a366d
--- /dev/null
+++ b/google_compute_engine/distro/tests/helpers_test.py
@@ -0,0 +1,66 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittest for helpers.py module."""
+
+import subprocess
+
+from google_compute_engine.distro import helpers
+from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import unittest
+
+
+class HelpersTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mock_logger = mock.Mock()
+
+  @mock.patch('google_compute_engine.distro.helpers.os.path.exists')
+  @mock.patch('google_compute_engine.distro.helpers.subprocess.check_call')
+  def testCallDhclient(self, mock_call, mock_exists):
+    mocks = mock.Mock()
+    mocks.attach_mock(mock_exists, 'exists')
+    mocks.attach_mock(mock_call, 'call')
+    mocks.attach_mock(self.mock_logger, 'logger')
+
+    mock_exists.side_effect = [False, True]
+    mock_call.side_effect = [
+        None, None, None, None, None, None,
+        subprocess.CalledProcessError(1, 'Test'),
+    ]
+
+    helpers.CallDhclient(['a', 'b'], self.mock_logger, 'test_script')
+    helpers.CallDhclient(['c', 'd'], self.mock_logger, 'test_script')
+    helpers.CallDhclient(['e', 'f'], self.mock_logger, None)
+    helpers.CallDhclient(['g', 'h'], self.mock_logger, None)
+
+    expected_calls = [
+        mock.call.logger.info(mock.ANY, ['a', 'b']),
+        mock.call.exists('test_script'),
+        mock.call.call(['dhclient', '-x', 'a', 'b']),
+        mock.call.call(['dhclient', 'a', 'b']),
+        mock.call.logger.info(mock.ANY, ['c', 'd']),
+        mock.call.exists('test_script'),
+        mock.call.call(['dhclient', '-sf', 'test_script', '-x', 'c', 'd']),
+        mock.call.call(['dhclient', '-sf', 'test_script', 'c', 'd']),
+        mock.call.logger.info(mock.ANY, ['e', 'f']),
+        mock.call.call(['dhclient', '-x', 'e', 'f']),
+        mock.call.call(['dhclient', 'e', 'f']),
+        mock.call.logger.info(mock.ANY, ['g', 'h']),
+        mock.call.call(['dhclient', '-x', 'g', 'h']),
+        mock.call.logger.warning(mock.ANY, ['g', 'h']),
+    ]
+
+    self.assertEqual(mocks.mock_calls, expected_calls)
diff --git a/google_compute_engine/distro/utils.py b/google_compute_engine/distro/utils.py
new file mode 100644
index 0000000..08f856c
--- /dev/null
+++ b/google_compute_engine/distro/utils.py
@@ -0,0 +1,49 @@
+#!/usr/bin/python
+# Copyright 2018 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities that are distro specific."""
+
+import logging.handlers
+
+from google_compute_engine import logger as utils_logger
+from google_compute_engine import network_utils
+
+
+class Utils(object):
+  """Utilities used by Linux guest services."""
+
+  def __init__(self, debug=False, logger=None):
+    """Constructor.
+
+    Args:
+      debug: bool, True if debug output should write to the console.
+      logger: logger object, used to write to SysLog and serial port.
+    """
+    self.debug = debug
+    facility = logging.handlers.SysLogHandler.LOG_DAEMON
+    self.logger = logger or utils_logger.Logger(
+        name='google-utils', debug=self.debug, facility=facility)
+    self.network_utils = network_utils.NetworkUtils(logger=self.logger)
+
+  def EnableNetworkInterfaces(
+      self, interfaces, logger, dhclient_script=None):
+    """Enable the list of network interfaces.
+
+    Args:
+      interfaces: list of string, the output device names to enable.
+      logger: logger object, used to write to SysLog and serial port.
+      dhclient_script: string, the path to a dhclient script used by dhclient.
+    """
+    pass
diff --git a/google_compute_engine/network_setup/network_setup.py b/google_compute_engine/network_setup/network_setup.py
index 8058458..954fda4 100755
--- a/google_compute_engine/network_setup/network_setup.py
+++ b/google_compute_engine/network_setup/network_setup.py
@@ -15,11 +15,8 @@
 
 """Enables the network interfaces provided in metadata."""
 
-import fileinput
 import logging.handlers
 import optparse
-import os
-import re
 import subprocess
 
 from google_compute_engine import config_manager
@@ -27,6 +24,7 @@ from google_compute_engine import constants
 from google_compute_engine import logger
 from google_compute_engine import metadata_watcher
 from google_compute_engine import network_utils
+from google_compute_engine.compat import distro_utils
 
 
 class NetworkSetup(object):
@@ -50,70 +48,9 @@ class NetworkSetup(object):
         name='network-setup', debug=debug, facility=facility)
     self.watcher = metadata_watcher.MetadataWatcher(logger=self.logger)
     self.network_utils = network_utils.NetworkUtils(logger=self.logger)
+    self.distro_utils = distro_utils.Utils(debug=debug)
     self._SetupNetworkInterfaces()
 
-  def _ModifyInterface(
-      self, interface_config, config_key, config_value, replace=False):
-    """Write a value to a config file if not already present.
-
-    Args:
-      interface_config: string, the path to a config file.
-      config_key: string, the configuration key to set.
-      config_value: string, the value to set for the configuration key.
-      replace: bool, replace the configuration option if already present.
-    """
-    config_entry = '%s=%s' % (config_key, config_value)
-    if not open(interface_config).read().count(config_key):
-      with open(interface_config, 'a') as config:
-        config.write('%s\n' % config_entry)
-    elif replace:
-      for line in fileinput.input(interface_config, inplace=True):
-        print(re.sub(r'%s=.*' % config_key, config_entry, line.rstrip()))
-
-  def _DisableNetworkManager(self, interfaces):
-    """Disable network manager management on a list of network interfaces.
-
-    Args:
-      interfaces: list of string, the output device names enable.
-    """
-    for interface in interfaces:
-      interface_config = os.path.join(self.network_path, 'ifcfg-%s' % interface)
-      if os.path.exists(interface_config):
-        self._ModifyInterface(
-            interface_config, 'DEVICE', interface, replace=False)
-        self._ModifyInterface(
-            interface_config, 'NM_CONTROLLED', 'no', replace=True)
-      else:
-        with open(interface_config, 'w') as interface_file:
-          interface_content = [
-              '# Added by Google.',
-              'BOOTPROTO=none',
-              'DEFROUTE=no',
-              'DEVICE=%s' % interface,
-              'IPV6INIT=no',
-              'NM_CONTROLLED=no',
-              'NOZEROCONF=yes',
-              '',
-          ]
-          interface_file.write('\n'.join(interface_content))
-        self.logger.info('Created config file for interface %s.', interface)
-
-  def _ConfigureNetwork(self, interfaces):
-    """Enable the list of network interfaces.
-
-    Args:
-      interfaces: list of string, the output device names enable.
-    """
-    self.logger.info('Enabling the Ethernet interfaces %s.', interfaces)
-    dhclient_command = ['dhclient']
-    if os.path.exists(self.dhclient_script):
-      dhclient_command += ['-sf', self.dhclient_script]
-    try:
-      subprocess.check_call(dhclient_command + ['-x'] + interfaces)
-      subprocess.check_call(dhclient_command + interfaces)
-    except subprocess.CalledProcessError:
-      self.logger.warning('Could not enable interfaces %s.', interfaces)
-
   def _EnableNetworkInterfaces(self, interfaces):
     """Enable the list of network interfaces.
 
@@ -130,10 +67,11 @@ class NetworkSetup(object):
         subprocess.check_call([self.dhcp_command])
       except subprocess.CalledProcessError:
         self.logger.warning('Could not enable Ethernet interfaces.')
-    else:
-      if os.path.exists(self.network_path):
-        self._DisableNetworkManager(interfaces)
-      self._ConfigureNetwork(interfaces)
+      return
+
+    # Distro-specific setup for network interfaces.
+    self.distro_utils.EnableNetworkInterfaces(
+        interfaces, self.logger, dhclient_script=self.dhclient_script)
 
   def _SetupNetworkInterfaces(self):
     """Get network interfaces metadata and enable each Ethernet interface."""
diff --git a/google_compute_engine/network_setup/tests/network_setup_test.py b/google_compute_engine/network_setup/tests/network_setup_test.py
index ad6af9c..072dc00 100644
--- a/google_compute_engine/network_setup/tests/network_setup_test.py
+++ b/google_compute_engine/network_setup/tests/network_setup_test.py
@@ -15,13 +15,11 @@
 
 """Unittest for network_setup.py module."""
 
-import os
 import shutil
 import subprocess
 import tempfile
 
 from google_compute_engine.network_setup import network_setup
-from google_compute_engine.test_compat import builtin
 from google_compute_engine.test_compat import mock
 from google_compute_engine.test_compat import unittest
 
@@ -37,12 +35,14 @@ class NetworkSetupTest(unittest.TestCase):
     self.mock_ip_forwarding_utils = mock.Mock()
     self.mock_network_utils = mock.Mock()
     self.metadata_key = 'metadata_key'
+    self.mock_distro_utils = mock.Mock()
 
     self.mock_setup = mock.create_autospec(network_setup.NetworkSetup)
     self.mock_setup.logger = self.mock_logger
     self.mock_setup.watcher = self.mock_watcher
     self.mock_setup.network_utils = self.mock_network_utils
     self.mock_setup.network_interfaces = self.metadata_key
+    self.mock_setup.distro_utils = self.mock_distro_utils
     self.mock_setup.network_path = '/etc/sysconfig/network-scripts'
     self.mock_setup.dhclient_script = '/bin/script'
     self.mock_setup.dhcp_command = ''
@@ -63,6 +63,7 @@ class NetworkSetupTest(unittest.TestCase):
     mocks.attach_mock(mock_network_utils, 'network')
     with mock.patch.object(
         network_setup.NetworkSetup, '_SetupNetworkInterfaces'):
+
       network_setup.NetworkSetup(debug=True)
       expected_calls = [
           mock.call.logger.Logger(name=mock.ANY, debug=True, facility=mock.ANY),
@@ -71,107 +72,12 @@ class NetworkSetupTest(unittest.TestCase):
       ]
       self.assertEqual(mocks.mock_calls, expected_calls)
 
-  def testModifyInterface(self):
-    config_file = os.path.join(self.test_dir, 'config.cfg')
-    config_content = [
-        '# File comment.\n',
-        'A="apple"\n',
-        'B=banana\n',
-        'B=banana\n',
-    ]
-    with open(config_file, 'w') as config:
-      for line in config_content:
-        config.write(line)
-
-    # Write a value for an existing config without overriding it.
-    network_setup.NetworkSetup._ModifyInterface(
-        self.mock_setup, config_file, 'A', 'aardvark', replace=False)
-    self.assertEquals(open(config_file).readlines(), config_content)
-    # Write a value for a config that is not already set.
-    network_setup.NetworkSetup._ModifyInterface(
-        self.mock_setup, config_file, 'C', 'none', replace=False)
-    config_content.append('C=none\n')
-    self.assertEquals(open(config_file).readlines(), config_content)
-    # Write a value for an existing config with replacement.
-    network_setup.NetworkSetup._ModifyInterface(
-        self.mock_setup, config_file, 'A', 'aardvark', replace=True)
-    config_content[1] = 'A=aardvark\n'
-    self.assertEquals(open(config_file).readlines(), config_content)
-    # Write a value for an existing config with multiple occurrences.
-    network_setup.NetworkSetup._ModifyInterface(
-        self.mock_setup, config_file, 'B', '"banana"', replace=True)
-    config_content[2] = config_content[3] = 'B="banana"\n'
-    self.assertEquals(open(config_file).readlines(), config_content)
-
-  @mock.patch('google_compute_engine.network_setup.network_setup.os.path.exists')
-  def testDisableNetworkManager(self, mock_exists):
-    mock_open = mock.mock_open()
-    mocks = mock.Mock()
-    mocks.attach_mock(mock_exists, 'exists')
-    mocks.attach_mock(mock_open, 'open')
-    mocks.attach_mock(self.mock_logger, 'logger')
-    mocks.attach_mock(self.mock_setup._ModifyInterface, 'modify')
-    mock_exists.side_effect = [True, False]
-
-    with mock.patch('%s.open' % builtin, mock_open, create=False):
-      network_setup.NetworkSetup._DisableNetworkManager(
-          self.mock_setup, ['eth0', 'eth1'])
-      expected_calls = [
-          mock.call.exists('/etc/sysconfig/network-scripts/ifcfg-eth0'),
-          mock.call.modify(mock.ANY, 'DEVICE', 'eth0', replace=False),
-          mock.call.modify(mock.ANY, 'NM_CONTROLLED', 'no', replace=True),
-          mock.call.exists('/etc/sysconfig/network-scripts/ifcfg-eth1'),
-          mock.call.open('/etc/sysconfig/network-scripts/ifcfg-eth1', 'w'),
-          mock.call.open().__enter__(),
-          mock.call.open().write(mock.ANY),
-          mock.call.open().__exit__(None, None, None),
-          mock.call.logger.info(mock.ANY, 'eth1'),
-      ]
-      self.assertEqual(mocks.mock_calls, expected_calls)
-
   @mock.patch('google_compute_engine.network_setup.network_setup.subprocess.check_call')
-  @mock.patch('google_compute_engine.network_setup.network_setup.os.path.exists')
-  def testConfigureNetwork(self, mock_exists, mock_call):
+  def testEnableNetworkInterfaces(self, mock_call):
     mocks = mock.Mock()
-    mocks.attach_mock(mock_exists, 'exists')
     mocks.attach_mock(mock_call, 'call')
     mocks.attach_mock(self.mock_logger, 'logger')
-    mock_exists.side_effect = [True, False, False]
-    mock_call.side_effect = [
-        None, None, None, None, subprocess.CalledProcessError(1, 'Test')]
-
-    network_setup.NetworkSetup._ConfigureNetwork(self.mock_setup, ['a', 'b'])
-    network_setup.NetworkSetup._ConfigureNetwork(self.mock_setup, ['c'])
-    network_setup.NetworkSetup._ConfigureNetwork(self.mock_setup, [])
-    expected_calls = [
-        # Successfully configure the network using a managed dhclient script.
-        mock.call.logger.info(mock.ANY, ['a', 'b']),
-        mock.call.exists('/bin/script'),
-        mock.call.call(['dhclient', '-sf', '/bin/script', '-x', 'a', 'b']),
-        mock.call.call(['dhclient', '-sf', '/bin/script', 'a', 'b']),
-        # Successfully configure the network using the default dhclient script.
-        mock.call.logger.info(mock.ANY, ['c']),
-        mock.call.exists('/bin/script'),
-        mock.call.call(['dhclient', '-x', 'c']),
-        mock.call.call(['dhclient', 'c']),
-        # Exception while enabling the network interface.
-        mock.call.logger.info(mock.ANY, []),
-        mock.call.exists('/bin/script'),
-        mock.call.call(['dhclient', '-x']),
-        mock.call.logger.warning(mock.ANY, []),
-    ]
-    self.assertEqual(mocks.mock_calls, expected_calls)
-
-  @mock.patch('google_compute_engine.network_setup.network_setup.subprocess.check_call')
-  @mock.patch('google_compute_engine.network_setup.network_setup.os.path.exists')
-  def testEnableNetworkInterfaces(self, mock_exists, mock_call):
-    mocks = mock.Mock()
-    mocks.attach_mock(mock_exists, 'exists')
-    mocks.attach_mock(mock_call, 'call')
-    mocks.attach_mock(self.mock_logger, 'logger')
-    mocks.attach_mock(self.mock_setup._DisableNetworkManager, 'disable')
-    mocks.attach_mock(self.mock_setup._ConfigureNetwork, 'configure')
-    mock_exists.side_effect = [True, False]
+    mocks.attach_mock(self.mock_setup.distro_utils.EnableNetworkInterfaces, 'enable')
     mock_call.side_effect = [None, subprocess.CalledProcessError(1, 'Test')]
 
     # Return immediately with fewer than two interfaces.
@@ -191,13 +97,10 @@ class NetworkSetupTest(unittest.TestCase):
     self.mock_setup.dhcp_command = 'failure'
     network_setup.NetworkSetup._EnableNetworkInterfaces(
         self.mock_setup, ['G', 'H'])
-
     expected_calls = [
-        mock.call.exists('/etc/sysconfig/network-scripts'),
-        mock.call.disable(['A', 'B']),
-        mock.call.configure(['A', 'B']),
-        mock.call.exists('/etc/sysconfig/network-scripts'),
-        mock.call.configure(['C', 'D']),
+        # First calls with empty `interfaces` were no-ops.
+        mock.call.enable(['A', 'B'], mock.ANY, dhclient_script='/bin/script'),
+        mock.call.enable(['C', 'D'], mock.ANY, dhclient_script='/bin/script'),
         mock.call.call(['success']),
         mock.call.call(['failure']),
         mock.call.logger.warning(mock.ANY),
@@ -214,10 +117,10 @@ class NetworkSetupTest(unittest.TestCase):
         {'mac': '1'}, {'mac': '2'}, {'mac': '3'}, {}]
     self.mock_network_utils.GetNetworkInterface.side_effect = [
         'eth0', 'eth1', None, None]
-
     with mock.patch.object(
         network_setup.NetworkSetup, '_EnableNetworkInterfaces'):
       self.mock_setup.dhcp_command = 'command'
+
       network_setup.NetworkSetup._SetupNetworkInterfaces(self.mock_setup)
       expected_calls = [
           mock.call.watcher.GetMetadata(
diff --git a/google_compute_engine/test_compat.py b/google_compute_engine/test_compat.py
index 232be4c..71fb12a 100644
--- a/google_compute_engine/test_compat.py
+++ b/google_compute_engine/test_compat.py
@@ -37,3 +37,9 @@ else:
   import unittest2 as unittest
 
 builtin = 'builtins' if sys.version_info >= (3,) else '__builtin__'
+
+# Import the reload module to re-import modules for testing compat.
+if sys.version_info >= (3, 4):
+  from importlib import reload as reload_import
+else:
+  from imp import reload as reload_import
diff --git a/google_compute_engine/tests/compat_test.py b/google_compute_engine/tests/compat_test.py
index a25972f..6f7671d 100644
--- a/google_compute_engine/tests/compat_test.py
+++ b/google_compute_engine/tests/compat_test.py
@@ -13,11 +13,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Unittest for logger.py module."""
+"""Unittest for compat.py module."""
 
 import sys
 
+import google_compute_engine.compat
 from google_compute_engine.test_compat import mock
+from google_compute_engine.test_compat import reload_import
 from google_compute_engine.test_compat import unittest
 from google_compute_engine.test_compat import urlretrieve
 
@@ -66,6 +68,39 @@ class CompatTest(unittest.TestCase):
     else:
       pass
 
+  @mock.patch('google_compute_engine.compat.platform.linux_distribution')
+  def testDistroCompat(self, mock_call):
+    test_cases = {
+        ('debian', '8.10', ''):
+            google_compute_engine.distro.debian_8.utils,
+        ('debian', '9.3', ''):
+            google_compute_engine.distro.debian_9.utils,
+        ('SUSE Linux Enterprise Server ', '12', 'x86_64'):
+            google_compute_engine.distro.debian_9.utils,
+        ('CentOS Linux', '6.4.3', 'Core'):
+            google_compute_engine.distro.el_6.utils,
+        ('CentOS Linux', '7.4.1708', 'Core'):
+            google_compute_engine.distro.el_7.utils,
+        ('CentOS Linux', '8.4.3', 'Core'):
+            google_compute_engine.distro.debian_9.utils,
+        ('Red Hat Enterprise Linux Server', '6.3.2', ''):
+            google_compute_engine.distro.el_6.utils,
+        ('Red Hat Enterprise Linux Server', '7.4', ''):
+            google_compute_engine.distro.el_7.utils,
+        ('Red Hat Enterprise Linux Server', '8.5.1', ''):
+            google_compute_engine.distro.debian_9.utils,
+        ('', '', ''):
+            google_compute_engine.distro.debian_9.utils,
+        ('xxxx', 'xxxx', 'xxxx'):
+            google_compute_engine.distro.debian_9.utils,
+    }
+
+    for distro in test_cases:
+      mock_call.return_value = distro
+      reload_import(google_compute_engine.compat)
+      self.assertEqual(
+        test_cases[distro], google_compute_engine.compat.distro_utils)
+
 
 if __name__ == '__main__':
   unittest.main()
diff --git a/google_compute_engine/tests/file_utils_test.py b/google_compute_engine/tests/file_utils_test.py
index 0d67807..1b170a3 100644
--- a/google_compute_engine/tests/file_utils_test.py
+++ b/google_compute_engine/tests/file_utils_test.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Unittest for file_utils_test.py module."""
+"""Unittest for file_utils.py module."""
 
 from google_compute_engine import file_utils
 from google_compute_engine.test_compat import mock