migration: T6007: convert all migration scripts to load as module

(cherry picked from commit 26740a8d583f64dc0a27b59dd4ae303056972c0b)

4 files changed, 195 insertions, 272 deletions

diff --git a/src/migration-scripts/dns-dynamic/0-to-1 b/src/migration-scripts/dns-dynamic/0-to-1
index b7674a9c8..6a91b36af 100755..100644
--- a/src/migration-scripts/dns-dynamic/0-to-1
+++ b/src/migration-scripts/dns-dynamic/0-to-1
@@ -1,18 +1,17 @@
-#!/usr/bin/env python3
-
-# Copyright (C) 2023 VyOS maintainers and contributors
+# Copyright 2023-2024 VyOS maintainers and contributors <maintainers@vyos.io>
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 or later as
-# published by the Free Software Foundation.
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
 #
-# This program is distributed in the hope that it will be useful,
+# This library 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.
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
 #
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
 # T5144:
 # - migrate "service dns dynamic interface ..."
@@ -27,7 +26,6 @@
 # - apply service protocol mapping upfront, they are not 'auto-detected' anymore
 # - migrate web-options url to stricter format
 
-import sys
 import re
 from vyos.configtree import ConfigTree
 
@@ -45,84 +43,67 @@ service_protocol_mapping = {
     'zoneedit': 'zoneedit1'
 }
 
-if len(sys.argv) < 2:
-    print("Must specify file name!")
-    sys.exit(1)
-
-file_name = sys.argv[1]
-
-with open(file_name, 'r') as f:
-    config_file = f.read()
-
-config = ConfigTree(config_file)
-
 old_base_path = ['service', 'dns', 'dynamic', 'interface']
 new_base_path = ['service', 'dns', 'dynamic', 'address']
 
-if not config.exists(old_base_path):
-    # Nothing to do
-    sys.exit(0)
-
-# Migrate "service dns dynamic interface"
-#      to "service dns dynamic address"
-config.rename(old_base_path, new_base_path[-1])
-
-for address in config.list_nodes(new_base_path):
-    # Migrate "service dns dynamic interface <interface> rfc2136 <config> record"
-    #      to "service dns dynamic address <address> rfc2136 <config> host-name"
-    if config.exists(new_base_path + [address, 'rfc2136']):
-        for rfc_cfg in config.list_nodes(new_base_path + [address, 'rfc2136']):
-            if config.exists(new_base_path + [address, 'rfc2136', rfc_cfg, 'record']):
-                config.rename(new_base_path + [address, 'rfc2136', rfc_cfg, 'record'], 'host-name')
-
-    # Migrate "service dns dynamic interface <interface> service <config> login"
-    #      to "service dns dynamic address <address> service <config> username"
-    if config.exists(new_base_path + [address, 'service']):
-        for svc_cfg in config.list_nodes(new_base_path + [address, 'service']):
-            if config.exists(new_base_path + [address, 'service', svc_cfg, 'login']):
-                config.rename(new_base_path + [address, 'service', svc_cfg, 'login'], 'username')
-            # Apply global 'ipv6-enable' to per <config> 'ip-version: ipv6'
-            if config.exists(new_base_path + [address, 'ipv6-enable']):
-                config.set(new_base_path + [address, 'service', svc_cfg, 'ip-version'], 'ipv6')
-                config.delete(new_base_path + [address, 'ipv6-enable'])
-            # Apply service protocol mapping upfront, they are not 'auto-detected' anymore
-            if svc_cfg in service_protocol_mapping:
-                config.set(new_base_path + [address, 'service', svc_cfg, 'protocol'],
-                           service_protocol_mapping.get(svc_cfg))
-
-    # If use-web is set, then:
-    #   Move "service dns dynamic address <address> <service|rfc2136> <service> ..."
-    #     to "service dns dynamic address web <service|rfc2136> <service>-<address> ..."
-    #   Move "service dns dynamic address web use-web ..."
-    #     to "service dns dynamic address web web-options ..."
-    # Note: The config is named <service>-<address> to avoid name conflict with old entries
-    if config.exists(new_base_path + [address, 'use-web']):
-        for svc_type in ['rfc2136', 'service']:
-            if config.exists(new_base_path + [address, svc_type]):
-                config.set(new_base_path + ['web', svc_type])
-                config.set_tag(new_base_path + ['web', svc_type])
-                for svc_cfg in config.list_nodes(new_base_path + [address, svc_type]):
-                    config.copy(new_base_path + [address, svc_type, svc_cfg],
-                                new_base_path + ['web', svc_type, f'{svc_cfg}-{address}'])
-
-        # Multiple web-options were not supported, so copy only the first one
-        # Also, migrate web-options url to stricter format and transition
-        # checkip.dyndns.org to https://domains.google.com/checkip for better
-        # TLS support (see: https://github.com/ddclient/ddclient/issues/597)
-        if not config.exists(new_base_path + ['web', 'web-options']):
-            config.copy(new_base_path + [address, 'use-web'], new_base_path + ['web', 'web-options'])
-            if config.exists(new_base_path + ['web', 'web-options', 'url']):
-                url = config.return_value(new_base_path + ['web', 'web-options', 'url'])
-                if re.search("^(https?://)?checkip\.dyndns\.org", url):
-                    config.set(new_base_path + ['web', 'web-options', 'url'], 'https://domains.google.com/checkip')
-                if not url.startswith(('http://', 'https://')):
-                    config.set(new_base_path + ['web', 'web-options', 'url'], f'https://{url}')
-
-        config.delete(new_base_path + [address])
-
-try:
-    with open(file_name, 'w') as f:
-        f.write(config.to_string())
-except OSError as e:
-    print("Failed to save the modified config: {}".format(e))
-    sys.exit(1)
+def migrate(config: ConfigTree) -> None:
+    if not config.exists(old_base_path):
+        # Nothing to do
+        return
+
+    # Migrate "service dns dynamic interface"
+    #      to "service dns dynamic address"
+    config.rename(old_base_path, new_base_path[-1])
+
+    for address in config.list_nodes(new_base_path):
+        # Migrate "service dns dynamic interface <interface> rfc2136 <config> record"
+        #      to "service dns dynamic address <address> rfc2136 <config> host-name"
+        if config.exists(new_base_path + [address, 'rfc2136']):
+            for rfc_cfg in config.list_nodes(new_base_path + [address, 'rfc2136']):
+                if config.exists(new_base_path + [address, 'rfc2136', rfc_cfg, 'record']):
+                    config.rename(new_base_path + [address, 'rfc2136', rfc_cfg, 'record'], 'host-name')
+
+        # Migrate "service dns dynamic interface <interface> service <config> login"
+        #      to "service dns dynamic address <address> service <config> username"
+        if config.exists(new_base_path + [address, 'service']):
+            for svc_cfg in config.list_nodes(new_base_path + [address, 'service']):
+                if config.exists(new_base_path + [address, 'service', svc_cfg, 'login']):
+                    config.rename(new_base_path + [address, 'service', svc_cfg, 'login'], 'username')
+                # Apply global 'ipv6-enable' to per <config> 'ip-version: ipv6'
+                if config.exists(new_base_path + [address, 'ipv6-enable']):
+                    config.set(new_base_path + [address, 'service', svc_cfg, 'ip-version'], 'ipv6')
+                    config.delete(new_base_path + [address, 'ipv6-enable'])
+                # Apply service protocol mapping upfront, they are not 'auto-detected' anymore
+                if svc_cfg in service_protocol_mapping:
+                    config.set(new_base_path + [address, 'service', svc_cfg, 'protocol'],
+                               service_protocol_mapping.get(svc_cfg))
+
+        # If use-web is set, then:
+        #   Move "service dns dynamic address <address> <service|rfc2136> <service> ..."
+        #     to "service dns dynamic address web <service|rfc2136> <service>-<address> ..."
+        #   Move "service dns dynamic address web use-web ..."
+        #     to "service dns dynamic address web web-options ..."
+        # Note: The config is named <service>-<address> to avoid name conflict with old entries
+        if config.exists(new_base_path + [address, 'use-web']):
+            for svc_type in ['rfc2136', 'service']:
+                if config.exists(new_base_path + [address, svc_type]):
+                    config.set(new_base_path + ['web', svc_type])
+                    config.set_tag(new_base_path + ['web', svc_type])
+                    for svc_cfg in config.list_nodes(new_base_path + [address, svc_type]):
+                        config.copy(new_base_path + [address, svc_type, svc_cfg],
+                                    new_base_path + ['web', svc_type, f'{svc_cfg}-{address}'])
+
+            # Multiple web-options were not supported, so copy only the first one
+            # Also, migrate web-options url to stricter format and transition
+            # checkip.dyndns.org to https://domains.google.com/checkip for better
+            # TLS support (see: https://github.com/ddclient/ddclient/issues/597)
+            if not config.exists(new_base_path + ['web', 'web-options']):
+                config.copy(new_base_path + [address, 'use-web'], new_base_path + ['web', 'web-options'])
+                if config.exists(new_base_path + ['web', 'web-options', 'url']):
+                    url = config.return_value(new_base_path + ['web', 'web-options', 'url'])
+                    if re.search("^(https?://)?checkip\.dyndns\.org", url):
+                        config.set(new_base_path + ['web', 'web-options', 'url'], 'https://domains.google.com/checkip')
+                    if not url.startswith(('http://', 'https://')):
+                        config.set(new_base_path + ['web', 'web-options', 'url'], f'https://{url}')
+
+            config.delete(new_base_path + [address])
diff --git a/src/migration-scripts/dns-dynamic/1-to-2 b/src/migration-scripts/dns-dynamic/1-to-2
index 8b599b57a..5dca9e32f 100755..100644
--- a/src/migration-scripts/dns-dynamic/1-to-2
+++ b/src/migration-scripts/dns-dynamic/1-to-2
@@ -1,18 +1,17 @@
-#!/usr/bin/env python3
-
-# Copyright (C) 2023 VyOS maintainers and contributors
+# Copyright 2023-2024 VyOS maintainers and contributors <maintainers@vyos.io>
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 or later as
-# published by the Free Software Foundation.
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
 #
-# This program is distributed in the hope that it will be useful,
+# This library 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.
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
 #
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
 # T5708:
 # - migrate "service dns dynamic timeout ..."
@@ -21,50 +20,32 @@
 # - migrate "service dns dynamic address <interface> service <service> protocol dnsexit"
 #        to "service dns dynamic address <interface> service <service> protocol dnsexit2"
 
-import sys
 from vyos.configtree import ConfigTree
 
-if len(sys.argv) < 2:
-    print("Must specify file name!")
-    sys.exit(1)
-
-file_name = sys.argv[1]
-
-with open(file_name, 'r') as f:
-    config_file = f.read()
-
-config = ConfigTree(config_file)
-
 base_path = ['service', 'dns', 'dynamic']
 timeout_path = base_path + ['timeout']
 address_path = base_path + ['address']
 
-if not config.exists(base_path):
-    # Nothing to do
-    sys.exit(0)
-
-# Migrate "service dns dynamic timeout ..."
-#      to "service dns dynamic interval ..."
-if config.exists(timeout_path):
-    config.rename(timeout_path, 'interval')
-
-# Remove "service dns dynamic address <interface> web-options ..." when <interface> != "web"
-for address in config.list_nodes(address_path):
-    if config.exists(address_path + [address, 'web-options']) and address != 'web':
-        config.delete(address_path + [address, 'web-options'])
-
-# Migrate "service dns dynamic address <interface> service <service> protocol dnsexit"
-#      to "service dns dynamic address <interface> service <service> protocol dnsexit2"
-for address in config.list_nodes(address_path):
-    for svc_cfg in config.list_nodes(address_path + [address, 'service']):
-        if config.exists(address_path + [address, 'service', svc_cfg, 'protocol']):
-            protocol = config.return_value(address_path + [address, 'service', svc_cfg, 'protocol'])
-            if protocol == 'dnsexit':
-                config.set(address_path + [address, 'service', svc_cfg, 'protocol'], 'dnsexit2')
-
-try:
-    with open(file_name, 'w') as f:
-        f.write(config.to_string())
-except OSError as e:
-    print("Failed to save the modified config: {}".format(e))
-    sys.exit(1)
+def migrate(config: ConfigTree) -> None:
+    if not config.exists(base_path):
+        # Nothing to do
+        return
+
+    # Migrate "service dns dynamic timeout ..."
+    #      to "service dns dynamic interval ..."
+    if config.exists(timeout_path):
+        config.rename(timeout_path, 'interval')
+
+    # Remove "service dns dynamic address <interface> web-options ..." when <interface> != "web"
+    for address in config.list_nodes(address_path):
+        if config.exists(address_path + [address, 'web-options']) and address != 'web':
+            config.delete(address_path + [address, 'web-options'])
+
+    # Migrate "service dns dynamic address <interface> service <service> protocol dnsexit"
+    #      to "service dns dynamic address <interface> service <service> protocol dnsexit2"
+    for address in config.list_nodes(address_path):
+        for svc_cfg in config.list_nodes(address_path + [address, 'service']):
+            if config.exists(address_path + [address, 'service', svc_cfg, 'protocol']):
+                protocol = config.return_value(address_path + [address, 'service', svc_cfg, 'protocol'])
+                if protocol == 'dnsexit':
+                    config.set(address_path + [address, 'service', svc_cfg, 'protocol'], 'dnsexit2')
diff --git a/src/migration-scripts/dns-dynamic/2-to-3 b/src/migration-scripts/dns-dynamic/2-to-3
index 4e0aa37d5..9aafc41a4 100755..100644
--- a/src/migration-scripts/dns-dynamic/2-to-3
+++ b/src/migration-scripts/dns-dynamic/2-to-3
@@ -1,18 +1,17 @@
-#!/usr/bin/env python3
-
-# Copyright (C) 2023 VyOS maintainers and contributors
+# Copyright 2023-2024 VyOS maintainers and contributors <maintainers@vyos.io>
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 or later as
-# published by the Free Software Foundation.
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
 #
-# This program is distributed in the hope that it will be useful,
+# This library 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.
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
 #
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
 # T5791:
 # - migrate "service dns dynamic address web web-options ..."
@@ -23,7 +22,6 @@
 #        to "service dns dynamic name <service> address <interface> ..."
 # - normalize the all service names to conform with name constraints
 
-import sys
 import re
 from unicodedata import normalize
 from vyos.configtree import ConfigTree
@@ -41,79 +39,61 @@ def normalize_name(name):
 
     return name
 
-
-if len(sys.argv) < 2:
-    print("Must specify file name!")
-    sys.exit(1)
-
-file_name = sys.argv[1]
-
-with open(file_name, 'r') as f:
-    config_file = f.read()
-
-config = ConfigTree(config_file)
-
 base_path = ['service', 'dns', 'dynamic']
 address_path = base_path + ['address']
 name_path = base_path + ['name']
 
-if not config.exists(address_path):
-    # Nothing to do
-    sys.exit(0)
+def migrate(config: ConfigTree) -> None:
+    if not config.exists(address_path):
+        # Nothing to do
+        return
 
-# config.copy does not recursively create a path, so initialize the name path as tagged node
-if not config.exists(name_path):
-    config.set(name_path)
-    config.set_tag(name_path)
+    # config.copy does not recursively create a path, so initialize the name path as tagged node
+    if not config.exists(name_path):
+        config.set(name_path)
+        config.set_tag(name_path)
 
-for address in config.list_nodes(address_path):
+    for address in config.list_nodes(address_path):
 
-    address_path_tag = address_path + [address]
+        address_path_tag = address_path + [address]
+
+        # Move web-option as a configuration in each service instead of top level web-option
+        if config.exists(address_path_tag + ['web-options']) and address == 'web':
+            for svc_type in ['service', 'rfc2136']:
+                if config.exists(address_path_tag + [svc_type]):
+                    for svc_cfg in config.list_nodes(address_path_tag + [svc_type]):
+                        config.copy(address_path_tag + ['web-options'],
+                                    address_path_tag + [svc_type, svc_cfg, 'web-options'])
+            config.delete(address_path_tag + ['web-options'])
 
-    # Move web-option as a configuration in each service instead of top level web-option
-    if config.exists(address_path_tag + ['web-options']) and address == 'web':
         for svc_type in ['service', 'rfc2136']:
             if config.exists(address_path_tag + [svc_type]):
+                # Set protocol to 'nsupdate' for RFC2136 configuration
+                if svc_type == 'rfc2136':
+                    for rfc_cfg in config.list_nodes(address_path_tag + ['rfc2136']):
+                        config.set(address_path_tag + ['rfc2136', rfc_cfg, 'protocol'], 'nsupdate')
+
+                # Add address as config value in each service before moving the service path
+                # And then copy the services from 'address <interface> service <service>'
+                #                              to 'name (service|rfc2136)-<service>-<address>'
+                # Note: The new service is named (service|rfc2136)-<service>-<address>
+                #       to avoid name conflict with old entries
                 for svc_cfg in config.list_nodes(address_path_tag + [svc_type]):
-                    config.copy(address_path_tag + ['web-options'],
-                                address_path_tag + [svc_type, svc_cfg, 'web-options'])
-        config.delete(address_path_tag + ['web-options'])
-
-    for svc_type in ['service', 'rfc2136']:
-        if config.exists(address_path_tag + [svc_type]):
-            # Set protocol to 'nsupdate' for RFC2136 configuration
-            if svc_type == 'rfc2136':
-                for rfc_cfg in config.list_nodes(address_path_tag + ['rfc2136']):
-                    config.set(address_path_tag + ['rfc2136', rfc_cfg, 'protocol'], 'nsupdate')
-
-            # Add address as config value in each service before moving the service path
-            # And then copy the services from 'address <interface> service <service>'
-            #                              to 'name (service|rfc2136)-<service>-<address>'
-            # Note: The new service is named (service|rfc2136)-<service>-<address>
-            #       to avoid name conflict with old entries
-            for svc_cfg in config.list_nodes(address_path_tag + [svc_type]):
-                config.set(address_path_tag + [svc_type, svc_cfg, 'address'], address)
-                config.copy(address_path_tag + [svc_type, svc_cfg],
-                            name_path + ['-'.join([svc_type, svc_cfg, address])])
-
-# Finally cleanup the old address path
-config.delete(address_path)
-
-# Normalize the all service names to conform with name constraints
-index = 1
-for name in config.list_nodes(name_path):
-    new_name = normalize_name(name)
-    if new_name != name:
-        # Append index if there is still a name conflicts after normalization
-        # For example, "foo-?(" and "foo-!)" both normalize to "foo-"
-        if config.exists(name_path + [new_name]):
-            new_name = f'{new_name}-{index}'
-            index += 1
-        config.rename(name_path + [name], new_name)
-
-try:
-    with open(file_name, 'w') as f:
-        f.write(config.to_string())
-except OSError as e:
-    print("Failed to save the modified config: {}".format(e))
-    sys.exit(1)
+                    config.set(address_path_tag + [svc_type, svc_cfg, 'address'], address)
+                    config.copy(address_path_tag + [svc_type, svc_cfg],
+                                name_path + ['-'.join([svc_type, svc_cfg, address])])
+
+    # Finally cleanup the old address path
+    config.delete(address_path)
+
+    # Normalize the all service names to conform with name constraints
+    index = 1
+    for name in config.list_nodes(name_path):
+        new_name = normalize_name(name)
+        if new_name != name:
+            # Append index if there is still a name conflicts after normalization
+            # For example, "foo-?(" and "foo-!)" both normalize to "foo-"
+            if config.exists(name_path + [new_name]):
+                new_name = f'{new_name}-{index}'
+                index += 1
+            config.rename(name_path + [name], new_name)
diff --git a/src/migration-scripts/dns-dynamic/3-to-4 b/src/migration-scripts/dns-dynamic/3-to-4
index b888a3b6b..c8e1ffeee 100755..100644
--- a/src/migration-scripts/dns-dynamic/3-to-4
+++ b/src/migration-scripts/dns-dynamic/3-to-4
@@ -1,18 +1,17 @@
-#!/usr/bin/env python3
-
-# Copyright (C) 2024 VyOS maintainers and contributors
+# Copyright 2024 VyOS maintainers and contributors <maintainers@vyos.io>
 #
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License version 2 or later as
-# published by the Free Software Foundation.
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
 #
-# This program is distributed in the hope that it will be useful,
+# This library 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.
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
 #
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
 # T5966:
 # - migrate "service dns dynamic name <service> address <interface>"
@@ -22,55 +21,37 @@
 #        to "service dns dynamic name <service> address web ..."
 #      when <interface> == 'web'
 
-import sys
 from vyos.configtree import ConfigTree
 
-if len(sys.argv) < 2:
-    print("Must specify file name!")
-    sys.exit(1)
-
-file_name = sys.argv[1]
-
-with open(file_name, 'r') as f:
-    config_file = f.read()
-
-config = ConfigTree(config_file)
-
 base_path = ['service', 'dns', 'dynamic', 'name']
 
-if not config.exists(base_path):
-    # Nothing to do
-    sys.exit(0)
-
-for service in config.list_nodes(base_path):
+def migrate(config: ConfigTree) -> None:
+    if not config.exists(base_path):
+        # Nothing to do
+        return
 
-    service_path = base_path + [service]
+    for service in config.list_nodes(base_path):
 
-    if config.exists(service_path + ['address']):
-        address = config.return_value(service_path + ['address'])
-        # 'address' is not a leaf node anymore, delete it first
-        config.delete(service_path + ['address'])
+        service_path = base_path + [service]
 
-        # When address is an interface (not 'web'), move it to 'address interface'
-        if address != 'web':
-            config.set(service_path + ['address', 'interface'], address)
+        if config.exists(service_path + ['address']):
+            address = config.return_value(service_path + ['address'])
+            # 'address' is not a leaf node anymore, delete it first
+            config.delete(service_path + ['address'])
 
-        else: # address == 'web'
-            # Relocate optional 'web-options' directly under 'address web'
-            if config.exists(service_path + ['web-options']):
-                # config.copy does not recursively create a path, so initialize it
-                config.set(service_path + ['address'])
-                config.copy(service_path + ['web-options'],
-                            service_path + ['address', 'web'])
-                config.delete(service_path + ['web-options'])
+            # When address is an interface (not 'web'), move it to 'address interface'
+            if address != 'web':
+                config.set(service_path + ['address', 'interface'], address)
 
-            # ensure that valueless 'address web' still exists even if there are no 'web-options'
-            if not config.exists(service_path + ['address', 'web']):
-                config.set(service_path + ['address', 'web'])
+            else: # address == 'web'
+                # Relocate optional 'web-options' directly under 'address web'
+                if config.exists(service_path + ['web-options']):
+                    # config.copy does not recursively create a path, so initialize it
+                    config.set(service_path + ['address'])
+                    config.copy(service_path + ['web-options'],
+                                service_path + ['address', 'web'])
+                    config.delete(service_path + ['web-options'])
 
-try:
-    with open(file_name, 'w') as f:
-        f.write(config.to_string())
-except OSError as e:
-    print("Failed to save the modified config: {}".format(e))
-    sys.exit(1)
+                # ensure that valueless 'address web' still exists even if there are no 'web-options'
+                if not config.exists(service_path + ['address', 'web']):
+                    config.set(service_path + ['address', 'web'])