diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile.py
index d9e79e2d2eeb..4ae1aa042b59 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile.py
@@ -27,7 +27,7 @@ class ContainerServiceLinuxProfile(Model):
     """
 
     _validation = {
-        'admin_username': {'required': True, 'pattern': r'^[a-z][a-z0-9_-]*$'},
+        'admin_username': {'required': True, 'pattern': r'^[A-Za-z][-A-Za-z0-9_]*$'},
         'ssh': {'required': True},
     }
 
diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile_py3.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile_py3.py
index 824f20d0da8b..9756107e1c7c 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile_py3.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/models/container_service_linux_profile_py3.py
@@ -27,7 +27,7 @@ class ContainerServiceLinuxProfile(Model):
     """
 
     _validation = {
-        'admin_username': {'required': True, 'pattern': r'^[a-z][a-z0-9_-]*$'},
+        'admin_username': {'required': True, 'pattern': r'^[A-Za-z][-A-Za-z0-9_]*$'},
         'ssh': {'required': True},
     }
 
diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/container_services_operations.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/container_services_operations.py
index 9901518494b7..887569a8a13a 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/container_services_operations.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/container_services_operations.py
@@ -78,7 +78,7 @@ def internal_paging(next_link=None, raw=False):
 
             # Construct headers
             header_parameters = {}
-            header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+            header_parameters['Accept'] = 'application/json'
             if self.config.generate_client_request_id:
                 header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
             if custom_headers:
@@ -87,9 +87,8 @@ def internal_paging(next_link=None, raw=False):
                 header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
             # Construct and send request
-            request = self._client.get(url, query_parameters)
-            response = self._client.send(
-                request, header_parameters, stream=False, **operation_config)
+            request = self._client.get(url, query_parameters, header_parameters)
+            response = self._client.send(request, stream=False, **operation_config)
 
             if response.status_code not in [200]:
                 exp = CloudError(response)
@@ -129,6 +128,7 @@ def _create_or_update_initial(
 
         # Construct headers
         header_parameters = {}
+        header_parameters['Accept'] = 'application/json'
         header_parameters['Content-Type'] = 'application/json; charset=utf-8'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
@@ -141,9 +141,8 @@ def _create_or_update_initial(
         body_content = self._serialize.body(parameters, 'ContainerService')
 
         # Construct and send request
-        request = self._client.put(url, query_parameters)
-        response = self._client.send(
-            request, header_parameters, body_content, stream=False, **operation_config)
+        request = self._client.put(url, query_parameters, header_parameters, body_content)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200, 201, 202]:
             exp = CloudError(response)
@@ -261,7 +260,7 @@ def get(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -270,8 +269,8 @@ def get(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.get(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.get(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -310,7 +309,6 @@ def _delete_initial(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -319,8 +317,8 @@ def _delete_initial(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.delete(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.delete(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [202, 204]:
             exp = CloudError(response)
@@ -424,7 +422,7 @@ def internal_paging(next_link=None, raw=False):
 
             # Construct headers
             header_parameters = {}
-            header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+            header_parameters['Accept'] = 'application/json'
             if self.config.generate_client_request_id:
                 header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
             if custom_headers:
@@ -433,9 +431,8 @@ def internal_paging(next_link=None, raw=False):
                 header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
             # Construct and send request
-            request = self._client.get(url, query_parameters)
-            response = self._client.send(
-                request, header_parameters, stream=False, **operation_config)
+            request = self._client.get(url, query_parameters, header_parameters)
+            response = self._client.send(request, stream=False, **operation_config)
 
             if response.status_code not in [200]:
                 exp = CloudError(response)
@@ -498,7 +495,7 @@ def list_orchestrators(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -507,8 +504,8 @@ def list_orchestrators(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.get(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.get(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/managed_clusters_operations.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/managed_clusters_operations.py
index 891d77138aa7..ee38a71b40e3 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/managed_clusters_operations.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/managed_clusters_operations.py
@@ -76,7 +76,7 @@ def internal_paging(next_link=None, raw=False):
 
             # Construct headers
             header_parameters = {}
-            header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+            header_parameters['Accept'] = 'application/json'
             if self.config.generate_client_request_id:
                 header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
             if custom_headers:
@@ -85,9 +85,8 @@ def internal_paging(next_link=None, raw=False):
                 header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
             # Construct and send request
-            request = self._client.get(url, query_parameters)
-            response = self._client.send(
-                request, header_parameters, stream=False, **operation_config)
+            request = self._client.get(url, query_parameters, header_parameters)
+            response = self._client.send(request, stream=False, **operation_config)
 
             if response.status_code not in [200]:
                 exp = CloudError(response)
@@ -148,7 +147,7 @@ def internal_paging(next_link=None, raw=False):
 
             # Construct headers
             header_parameters = {}
-            header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+            header_parameters['Accept'] = 'application/json'
             if self.config.generate_client_request_id:
                 header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
             if custom_headers:
@@ -157,9 +156,8 @@ def internal_paging(next_link=None, raw=False):
                 header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
             # Construct and send request
-            request = self._client.get(url, query_parameters)
-            response = self._client.send(
-                request, header_parameters, stream=False, **operation_config)
+            request = self._client.get(url, query_parameters, header_parameters)
+            response = self._client.send(request, stream=False, **operation_config)
 
             if response.status_code not in [200]:
                 exp = CloudError(response)
@@ -216,7 +214,7 @@ def get_upgrade_profile(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -225,8 +223,8 @@ def get_upgrade_profile(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.get(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.get(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -286,7 +284,7 @@ def get_access_profile(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -295,8 +293,8 @@ def get_access_profile(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.post(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.post(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -351,7 +349,7 @@ def list_cluster_admin_credentials(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -360,8 +358,8 @@ def list_cluster_admin_credentials(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.post(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.post(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -416,7 +414,7 @@ def list_cluster_user_credentials(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -425,8 +423,8 @@ def list_cluster_user_credentials(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.post(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.post(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -481,7 +479,7 @@ def get(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+        header_parameters['Accept'] = 'application/json'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -490,8 +488,8 @@ def get(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.get(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.get(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -528,6 +526,7 @@ def _create_or_update_initial(
 
         # Construct headers
         header_parameters = {}
+        header_parameters['Accept'] = 'application/json'
         header_parameters['Content-Type'] = 'application/json; charset=utf-8'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
@@ -540,9 +539,8 @@ def _create_or_update_initial(
         body_content = self._serialize.body(parameters, 'ManagedCluster')
 
         # Construct and send request
-        request = self._client.put(url, query_parameters)
-        response = self._client.send(
-            request, header_parameters, body_content, stream=False, **operation_config)
+        request = self._client.put(url, query_parameters, header_parameters, body_content)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200, 201]:
             exp = CloudError(response)
@@ -636,6 +634,7 @@ def _update_tags_initial(
 
         # Construct headers
         header_parameters = {}
+        header_parameters['Accept'] = 'application/json'
         header_parameters['Content-Type'] = 'application/json; charset=utf-8'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
@@ -648,9 +647,8 @@ def _update_tags_initial(
         body_content = self._serialize.body(parameters, 'TagsObject')
 
         # Construct and send request
-        request = self._client.patch(url, query_parameters)
-        response = self._client.send(
-            request, header_parameters, body_content, stream=False, **operation_config)
+        request = self._client.patch(url, query_parameters, header_parameters, body_content)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [200]:
             exp = CloudError(response)
@@ -738,7 +736,6 @@ def _delete_initial(
 
         # Construct headers
         header_parameters = {}
-        header_parameters['Content-Type'] = 'application/json; charset=utf-8'
         if self.config.generate_client_request_id:
             header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
         if custom_headers:
@@ -747,8 +744,8 @@ def _delete_initial(
             header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
         # Construct and send request
-        request = self._client.delete(url, query_parameters)
-        response = self._client.send(request, header_parameters, stream=False, **operation_config)
+        request = self._client.delete(url, query_parameters, header_parameters)
+        response = self._client.send(request, stream=False, **operation_config)
 
         if response.status_code not in [202, 204]:
             exp = CloudError(response)
diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/operations.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/operations.py
index 83337ae0311b..a43ead3a313c 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/operations.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/operations/operations.py
@@ -67,7 +67,7 @@ def internal_paging(next_link=None, raw=False):
 
             # Construct headers
             header_parameters = {}
-            header_parameters['Content-Type'] = 'application/json; charset=utf-8'
+            header_parameters['Accept'] = 'application/json'
             if self.config.generate_client_request_id:
                 header_parameters['x-ms-client-request-id'] = str(uuid.uuid1())
             if custom_headers:
@@ -76,9 +76,8 @@ def internal_paging(next_link=None, raw=False):
                 header_parameters['accept-language'] = self._serialize.header("self.config.accept_language", self.config.accept_language, 'str')
 
             # Construct and send request
-            request = self._client.get(url, query_parameters)
-            response = self._client.send(
-                request, header_parameters, stream=False, **operation_config)
+            request = self._client.get(url, query_parameters, header_parameters)
+            response = self._client.send(request, stream=False, **operation_config)
 
             if response.status_code not in [200]:
                 exp = CloudError(response)
diff --git a/azure-mgmt-containerservice/azure/mgmt/containerservice/version.py b/azure-mgmt-containerservice/azure/mgmt/containerservice/version.py
index 001170437cef..204d7f82b78a 100644
--- a/azure-mgmt-containerservice/azure/mgmt/containerservice/version.py
+++ b/azure-mgmt-containerservice/azure/mgmt/containerservice/version.py
@@ -9,5 +9,5 @@
 # regenerated.
 # --------------------------------------------------------------------------
 
-VERSION = "4.2.0"
+VERSION = "4.1.0"