System-Setup: Add systemd experimental support to WSL

Grow a new API for enabling/disabling systemd experimental support. We
do this by chaining a specific command= in the boot section.
We preserve the user customized command= content when systemd
experimental support is not enabled.

Co-authored-by: Jean-Baptiste Lallement <jean-baptiste@ubuntu.com>

autoinstall-system-setup-schema.json

@@ -99,6 +99,9 @@
                 },
                 "automount_mountfstab": {
                     "type": "boolean"
+                },
+                "systemd_enabled": {
+                    "type": "boolean"
                 }
             },
             "additionalProperties": false

examples/answers-system-setup-reconf.yaml

@@ -8,5 +8,6 @@ WSLConfigurationAdvanced:
   interop_appendwindowspath: false
   automount_enabled: false
   automount_mountfstab: false
+  systemd_enabled: true
 Summary:
   reboot: yes

examples/autoinstall-system-setup-full.yaml

@@ -19,4 +19,5 @@ wslconfadvanced:
   interop_appendwindowspath: false
   automount_enabled: false
   automount_mountfstab: false
+  systemd_enabled: true
 shutdown: 'poweroff'

subiquity/common/types.py

@@ -458,3 +458,4 @@ class WSLConfigurationAdvanced:
     automount_mountfstab:  bool = attr.ib(default=True)
     interop_enabled:  bool = attr.ib(default=True)
     interop_appendwindowspath: bool = attr.ib(default=True)
+    systemd_enabled:  bool = attr.ib(default=False)

system_setup/client/controllers/wslconfadvanced.py

@@ -32,7 +32,8 @@ class WSLConfigurationAdvancedController(SubiquityTuiController):
     def run_answers(self):
         if all(elem in self.answers for elem in
                ['interop_enabled', 'interop_appendwindowspath',
-                'automount_enabled', 'automount_mountfstab']):
+                'automount_enabled', 'automount_mountfstab',
+                'systemd_enabled']):
 
             reconfiguration = WSLConfigurationAdvanced(**self.answers)
             self.done(reconfiguration)

system_setup/common/wsl_conf.py

@@ -24,6 +24,8 @@ from configparser import ConfigParser
 
 log = logging.getLogger("system_setup.common.wsl_conf")
 
+WSL_SYSTEMD_BOOT_COMMAND = "/usr/libexec/wsl-systemd"
+
 config_base_default = {
     "wsl": {
         "automount": {
@@ -46,6 +48,9 @@ config_adv_default = {
         "interop": {
             "enabled": "true",
             "appendwindowspath": "true"
+        },
+        "boot": {
+            "command": ""
         }
     }
 }
@@ -74,9 +79,20 @@ def wsl_config_loader(data, config_ref, id):
             conf_sec_list = config[conf_sec]
             for conf_item in conf_sec_list:
                 if conf_item in config_ref[id][conf_sec]:
+                    # Handle systemd experimental feature (string -> bool)
+                    if (
+                            conf_sec.lower() == "boot" and
+                            conf_item.lower() == "command"):
+                        v = conf_sec_list[conf_item]
+                        data["systemd_enabled"] = "false"
+                        if v == WSL_SYSTEMD_BOOT_COMMAND:
+                            data["systemd_enabled"] = "true"
+                        continue
                     data[conf_sec.lower()
                          + "_" + conf_item.lower()] = \
-                             conf_sec_list[conf_item]
+                        conf_sec_list[conf_item]
+    # This is the systemd value we converted
+    data.pop("boot_command", None)
     return data
 
 
@@ -128,9 +144,31 @@ def wsl_config_update(config_class, root_dir):
                 config_default_value = config_settings[config_setting]
                 config_api_name = \
                     config_section.lower() + "_" + config_setting.lower()
+
+                # on systemd, select correct API endpoint
+                systemd_experimental_section = False
+                if (config_section.lower() == "boot" and
+                   config_setting.lower() == "command"):
+                    systemd_experimental_section = True
+                    config_api_name = "systemd_enabled"
+
                 config_value = config_class.__dict__[config_api_name]
                 if isinstance(config_value, bool):
                     config_value = str(config_value).lower()
+
+                # map systemd bool -> boot command string and keep old value
+                # if it was not set to wsl-systemd (user customized)
+                if systemd_experimental_section:
+                    v = ""
+                    # Keep previous value set by user if the option is kept
+                    # disabled and they set their own boot command.
+                    if (config.has_option("boot", "command") and
+                       config["boot"]["command"] != WSL_SYSTEMD_BOOT_COMMAND):
+                        v = config["boot"]["command"]
+                    if config_value == "true":
+                        v = WSL_SYSTEMD_BOOT_COMMAND
+                    config_value = v
+
                 # if the value for the setting is default value, drop it
                 if config_default_value == config_value:
                     if config_section in config:

system_setup/models/wslconfadvanced.py

@@ -25,6 +25,7 @@ class WSLConfigurationAdvanced(object):
     interop_appendwindowspath = attr.ib()
     automount_enabled = attr.ib()
     automount_mountfstab = attr.ib()
+    systemd_enabled = attr.ib()
 
 
 class WSLConfigurationAdvancedModel(object):

system_setup/server/controllers/wslconfadvanced.py

@@ -39,7 +39,8 @@ class WSLConfigurationAdvancedController(SubiquityController):
             'interop_enabled': {'type': 'boolean'},
             'interop_appendwindowspath': {'type': 'boolean'},
             'automount_enabled': {'type': 'boolean'},
-            'automount_mountfstab': {'type': 'boolean'}
+            'automount_mountfstab': {'type': 'boolean'},
+            'systemd_enabled': {'type': 'boolean'}
         },
         'additionalProperties': False,
     }
@@ -80,6 +81,8 @@ class WSLConfigurationAdvancedController(SubiquityController):
                 self.model.wslconfadvanced.automount_enabled
             data.automount_mountfstab = \
                 self.model.wslconfadvanced.automount_mountfstab
+            data.systemd_enabled = \
+                self.model.wslconfadvanced.systemd_enabled
         return data
 
     async def POST(self, data: WSLConfigurationAdvanced):

system_setup/tests/golden/answers-reconf/wsl.conf

@@ -4,6 +4,9 @@ mountfstab = false
 options = metadata
 root = /custom_mnt_path
 
+[boot]
+command = /usr/libexec/wsl-systemd
+
 [interop]
 appendwindowspath = false
 enabled = false

system_setup/tests/golden/autoinstall-full/wsl.conf

@@ -4,6 +4,9 @@ mountfstab = false
 options = metadata
 root = /custom_mnt_path
 
+[boot]
+command = /usr/libexec/wsl-systemd
+
 [interop]
 appendwindowspath = false
 enabled = false

system_setup/ui/views/wslconfadvanced.py

@@ -59,6 +59,10 @@ class WSLConfigurationAdvancedForm(Form):
         BooleanField(_("Append Windows Path"),
                      help=_("Whether Windows Path will be append in the"
                             " PATH environment variable in WSL."))
+    systemd_enabled = \
+        BooleanField(_("Enable Systemd"),
+                     help=_("EXPERIMENTAL - Whether systemd should be"
+                            " activated at boot time."))
 
 
 class WSLConfigurationAdvancedView(BaseView):
@@ -78,6 +82,8 @@ class WSLConfigurationAdvancedView(BaseView):
                 configuration_data.automount_enabled,
             'automount_mountfstab':
                 configuration_data.automount_mountfstab,
+            'systemd_enabled':
+                configuration_data.systemd_enabled,
         }
         self.form = WSLConfigurationAdvancedForm(initial=initial)
 
@@ -101,4 +107,6 @@ class WSLConfigurationAdvancedView(BaseView):
             .automount_enabled.value,
             automount_mountfstab=self.form
             .automount_mountfstab.value,
+            systemd_enabled=self.form
+            .systemd_enabled.value,
             ))