add btrfs_set_default_volume attribute

By default kiwi runs btrfs set-default on the volume that is
considered the default volume according to the btrfs settings
and defaults. btrfs_set_default_volume="false" allows
to deactivate this action. Along with the change also the
misleading name of the btrfs_create_toplevel_subvolume has
been changed to root_is_subvolume

doc/source/image_description/elements.rst

@@ -412,11 +412,19 @@ btrfs_quota_groups="true|false":
   Boolean parameter to activate filesystem quotas if
   the filesystem is `btrfs`. By default quotas are inactive.
 
-btrfs_create_toplevel_subvolume="true|false":
-  Tell kiwi to nest all subvolumes below a toplevel volume.
-  The name of this toplevel volume is by default set to: `@`
-  The name of the toplevel volume can be changed via
-  a volume entry of the form
+btrfs_set_default_volume="true|false":
+  Tell kiwi to explicitly make a volume the default volume
+  This can be either `/` or the root subvolume or the root
+  snapshot depending on the specified btrfs configuration
+  attributes. By default btrfs_set_default_volume is set to: true
+  If no default volume should be set, this attribute can be
+  used to turn it off
+
+btrfs_root_is_subvolume="true|false":
+  Tell kiwi to create a root volume to host (/) inside.
+  The name of this subvolume is by default set to: `@`.
+  The name of the subvolume can be changed via a volume entry
+  of the form:
 
   .. code:: xml
 

kiwi/builder/disk.py

@@ -417,9 +417,12 @@ def create_disk(self) -> Result:
                 'root_is_readonly_snapshot':
                     self.xml_state.build_type.
                     get_btrfs_root_is_readonly_snapshot(),
-                'create_toplevel_subvolume':
+                'root_is_subvolume':
                     self.xml_state.build_type.
-                    get_btrfs_create_toplevel_subvolume(),
+                    get_btrfs_root_is_subvolume(),
+                'set_default_volume':
+                    self.xml_state.build_type.
+                    get_btrfs_set_default_volume(),
                 'quota_groups':
                     self.xml_state.build_type.get_btrfs_quota_groups(),
                 'resize_on_boot':

kiwi/schema/kiwi.rnc

@@ -1433,15 +1433,27 @@ div {
             sch:param [ name = "attr" value = "btrfs_quota_groups" ]
             sch:param [ name = "types" value = "oem" ]
         ]
-    k.type.btrfs_create_toplevel_subvolume =
-        ## Tell kiwi to nest all subvolumes below a toplevel volume.
-        ## The name of this toplevel volume is by default set to: '@'
-        ## The name of the toplevel volume can be changed via
-        ## a volume entry of the form '<volume name="@root=TOPLEVEL_NAME"/>'
-        ## By default the creation of a toplevel volume is set to: true
-        attribute btrfs_create_toplevel_subvolume { xsd:boolean }
-        >> sch:pattern [ id = "btrfs_create_toplevel_subvolume" is-a = "image_type"
-            sch:param [ name = "attr" value = "btrfs_create_toplevel_subvolume" ]
+    k.type.btrfs_set_default_volume.attribute =
+        ## Tell kiwi to explicitly make a volume the default volume
+        ## This can be either (/) or the root subvolume or the root
+        ## snapshot depending on the specified btrfs configuration
+        ## attributes. By default btrfs_set_default_volume is set to: true
+        ## If no default volume should be set, this attribute can be
+        ## used to turn it off
+        attribute btrfs_set_default_volume { xsd:boolean }
+        >> sch:pattern [ id = "btrfs_set_default_volume" is-a = "image_type"
+            sch:param [ name = "attr" value = "btrfs_set_default_volume" ]
+            sch:param [ name = "types" value = "oem" ]
+        ]
+    k.type.btrfs_root_is_subvolume.attribute =
+        ## Tell kiwi to create a root volume to host (/) inside.
+        ## The name of this subvolume is by default set to: '@'
+        ## The name of the subvolume can be changed via
+        ## a volume entry of the form '<volume name="@root=NAME"/>'
+        ## By default the creation of a root subvolume is set to: true
+        attribute btrfs_root_is_subvolume { xsd:boolean }
+        >> sch:pattern [ id = "btrfs_root_is_subvolume" is-a = "image_type"
+            sch:param [ name = "attr" value = "btrfs_root_is_subvolume" ]
             sch:param [ name = "types" value = "oem" ]
         ]
     k.type.btrfs_root_is_snapshot.attribute =
@@ -2229,7 +2241,8 @@ div {
         k.type.bootprofile.attribute? &
         k.type.btrfs_quota_groups.attribute? &
         k.type.btrfs_root_is_snapshot.attribute? &
-        k.type.btrfs_create_toplevel_subvolume? &
+        k.type.btrfs_root_is_subvolume.attribute? &
+        k.type.btrfs_set_default_volume.attribute? &
         k.type.btrfs_root_is_readonly_snapshot.attribute? &
         k.type.compressed.attribute? &
         k.type.devicepersistency.attribute? &

kiwi/schema/kiwi.rng

@@ -2093,17 +2093,32 @@ By default the quota system is inactive</a:documentation>
         <sch:param name="types" value="oem"/>
       </sch:pattern>
     </define>
-    <define name="k.type.btrfs_create_toplevel_subvolume">
-      <attribute name="btrfs_create_toplevel_subvolume">
-        <a:documentation>Tell kiwi to nest all subvolumes below a toplevel volume.
-The name of this toplevel volume is by default set to: '@'
-The name of the toplevel volume can be changed via
-a volume entry of the form '&lt;volume name="@root=TOPLEVEL_NAME"/&gt;'
-By default the creation of a toplevel volume is set to: true</a:documentation>
+    <define name="k.type.btrfs_set_default_volume.attribute">
+      <attribute name="btrfs_set_default_volume">
+        <a:documentation>Tell kiwi to explicitly make a volume the default volume
+This can be either (/) or the root subvolume or the root
+snapshot depending on the specified btrfs configuration
+attributes. By default btrfs_set_default_volume is set to: true
+If no default volume should be set, this attribute can be
+used to turn it off</a:documentation>
         <data type="boolean"/>
       </attribute>
-      <sch:pattern id="btrfs_create_toplevel_subvolume" is-a="image_type">
-        <sch:param name="attr" value="btrfs_create_toplevel_subvolume"/>
+      <sch:pattern id="btrfs_set_default_volume" is-a="image_type">
+        <sch:param name="attr" value="btrfs_set_default_volume"/>
+        <sch:param name="types" value="oem"/>
+      </sch:pattern>
+    </define>
+    <define name="k.type.btrfs_root_is_subvolume.attribute">
+      <attribute name="btrfs_root_is_subvolume">
+        <a:documentation>Tell kiwi to create a root volume to host (/) inside.
+The name of this subvolume is by default set to: '@'
+The name of the subvolume can be changed via
+a volume entry of the form '&lt;volume name="@root=NAME"/&gt;'
+By default the creation of a root subvolume is set to: true</a:documentation>
+        <data type="boolean"/>
+      </attribute>
+      <sch:pattern id="btrfs_root_is_subvolume" is-a="image_type">
+        <sch:param name="attr" value="btrfs_root_is_subvolume"/>
         <sch:param name="types" value="oem"/>
       </sch:pattern>
     </define>
@@ -3192,7 +3207,10 @@ kiwi-ng result bundle ...</a:documentation>
           <ref name="k.type.btrfs_root_is_snapshot.attribute"/>
         </optional>
         <optional>
-          <ref name="k.type.btrfs_create_toplevel_subvolume"/>
+          <ref name="k.type.btrfs_root_is_subvolume.attribute"/>
+        </optional>
+        <optional>
+          <ref name="k.type.btrfs_set_default_volume.attribute"/>
         </optional>
         <optional>
           <ref name="k.type.btrfs_root_is_readonly_snapshot.attribute"/>

kiwi/volume_manager/btrfs.py

@@ -67,10 +67,12 @@ def post_init(self, custom_args):
             self.custom_args['root_label'] = 'ROOT'
         if 'root_is_snapshot' not in self.custom_args:
             self.custom_args['root_is_snapshot'] = False
+        if 'set_default_volume' not in self.custom_args:
+            self.custom_args['set_default_volume'] = True
         if 'root_is_readonly_snapshot' not in self.custom_args:
             self.custom_args['root_is_readonly_snapshot'] = False
-        if 'create_toplevel_subvolume' not in self.custom_args:
-            self.custom_args['create_toplevel_subvolume'] = None
+        if 'root_is_subvolume' not in self.custom_args:
+            self.custom_args['root_is_subvolume'] = None
         if 'quota_groups' not in self.custom_args:
             self.custom_args['quota_groups'] = False
 
@@ -444,18 +446,18 @@ def set_property_readonly_root(self):
             )
 
     def _has_root_volume(self) -> bool:
-        has_root_volume = bool(self.custom_args['create_toplevel_subvolume'])
-        if self.custom_args['create_toplevel_subvolume'] is None:
-            # toplevel volume not explicitly configured, will
+        has_root_volume = bool(self.custom_args['root_is_subvolume'])
+        if self.custom_args['root_is_subvolume'] is None:
+            # root volume not explicitly configured, will
             # be enabled by default but this is going to change
             # in the future. Print a deprecation message to inform
             # the user about a potential behavior change
-            log.warning("Implicitly creating a toplevel volume")
+            log.warning("Implicitly creating root volume")
             log.warning(
                 "--> Future versions of kiwi will not do this anymore"
             )
             log.warning(
-                "--> Please specify btrfs_create_toplevel_subvolume true|false"
+                "--> Please specify btrfs_root_is_subvolume true|false"
             )
             has_root_volume = True
         return has_root_volume
@@ -468,26 +470,27 @@ def _is_volume_enabled_for_fs_check(self, mountpoint):
         return False
 
     def _set_default_volume(self, default_volume):
-        subvolume_list_call = Command.run(
-            ['btrfs', 'subvolume', 'list', self.mountpoint]
-        )
-        for subvolume in subvolume_list_call.output.split('\n'):
-            id_search = re.search('ID (\d+) .*path (.*)', subvolume)
-            if id_search:
-                volume_id = id_search.group(1)
-                volume_path = id_search.group(2)
-                if volume_path == default_volume:
-                    Command.run(
-                        [
-                            'btrfs', 'subvolume', 'set-default',
-                            volume_id, self.mountpoint
-                        ]
-                    )
-                    return
+        if self.custom_args['set_default_volume']:
+            subvolume_list_call = Command.run(
+                ['btrfs', 'subvolume', 'list', self.mountpoint]
+            )
+            for subvolume in subvolume_list_call.output.split('\n'):
+                id_search = re.search('ID (\d+) .*path (.*)', subvolume)
+                if id_search:
+                    volume_id = id_search.group(1)
+                    volume_path = id_search.group(2)
+                    if volume_path == default_volume:
+                        Command.run(
+                            [
+                                'btrfs', 'subvolume', 'set-default',
+                                volume_id, self.mountpoint
+                            ]
+                        )
+                        return
 
-        raise KiwiVolumeRootIDError(
-            'Failed to find btrfs volume: %s' % default_volume
-        )
+            raise KiwiVolumeRootIDError(
+                'Failed to find btrfs volume: %s' % default_volume
+            )
 
     def _xml_pretty(self, toplevel_element):
         xml_data_unformatted = ElementTree.tostring(