Get host dmesg as host logs (#1606)

* Get host dmesg as host logs

* fix lint

API.md

@@ -252,6 +252,10 @@ return:
 }
 ```
 
+- GET `/host/logs`
+
+Return host dmesg
+
 - POST `/host/options`
 
 ```json

supervisor/api/__init__.py

@@ -74,6 +74,7 @@ class RestAPI(CoreSysAttributes):
         self.webapp.add_routes(
             [
                 web.get("/host/info", api_host.info),
+                web.get("/host/logs", api_host.logs),
                 web.post("/host/reboot", api_host.reboot),
                 web.post("/host/shutdown", api_host.shutdown),
                 web.post("/host/reload", api_host.reload),

supervisor/api/host.py

@@ -1,24 +1,27 @@
 """Init file for Supervisor host RESTful API."""
 import asyncio
 import logging
+from typing import Awaitable
 
+from aiohttp import web
 import voluptuous as vol
 
-from .utils import api_process, api_validate
 from ..const import (
-    ATTR_HOSTNAME,
-    ATTR_FEATURES,
-    ATTR_KERNEL,
-    ATTR_OPERATING_SYSTEM,
     ATTR_CHASSIS,
-    ATTR_DEPLOYMENT,
-    ATTR_STATE,
-    ATTR_NAME,
-    ATTR_DESCRIPTON,
-    ATTR_SERVICES,
     ATTR_CPE,
+    ATTR_DEPLOYMENT,
+    ATTR_DESCRIPTON,
+    ATTR_FEATURES,
+    ATTR_HOSTNAME,
+    ATTR_KERNEL,
+    ATTR_NAME,
+    ATTR_OPERATING_SYSTEM,
+    ATTR_SERVICES,
+    ATTR_STATE,
+    CONTENT_TYPE_BINARY,
 )
 from ..coresys import CoreSysAttributes
+from .utils import api_process, api_process_raw, api_validate
 
 _LOGGER: logging.Logger = logging.getLogger(__name__)
 
@@ -107,3 +110,8 @@ class APIHost(CoreSysAttributes):
         """Restart a service."""
         unit = request.match_info.get(SERVICE)
         return asyncio.shield(self.sys_host.services.restart(unit))
+
+    @api_process_raw(CONTENT_TYPE_BINARY)
+    def logs(self, request: web.Request) -> Awaitable[bytes]:
+        """Return host kernel logs."""
+        return self.sys_host.info.get_dmesg()

supervisor/host/info.py

@@ -1,9 +1,15 @@
 """Info control for host."""
+import asyncio
 import logging
 from typing import Optional
 
 from ..coresys import CoreSysAttributes
-from ..exceptions import HostNotSupportedError, DBusNotConnectedError, DBusError
+from ..exceptions import (
+    HostNotSupportedError,
+    HostError,
+    DBusNotConnectedError,
+    DBusError,
+)
 
 _LOGGER: logging.Logger = logging.getLogger(__name__)
 
@@ -45,6 +51,21 @@ class InfoCenter(CoreSysAttributes):
         """Return local CPE."""
         return self.sys_dbus.hostname.cpe
 
+    async def get_dmesg(self) -> bytes:
+        """Return host dmesg output."""
+        proc = await asyncio.create_subprocess_shell(
+            "dmesg", stdout=asyncio.subprocess.PIPE, stderr=asyncio.subprocess.STDOUT
+        )
+
+        # Get kernel log
+        try:
+            stdout, _ = await proc.communicate()
+        except OSError as err:
+            _LOGGER.error("Can't read kernel log: %s", err)
+            raise HostError()
+
+        return stdout
+
     async def update(self):
         """Update properties over dbus."""
         _LOGGER.info("Update local host information")