content: usage: advanced: document system logs

content/usage/advanced/index.md

@@ -475,6 +475,8 @@ and imported to new Cockpit instances/devices later.
 
 ## Logs
 
+### Telemetry Logs and Subtitle Files
+
 Cockpit can optionally record some of its received telemetry values, which can then be turned into subtitle
 files when recording videos. 
 
@@ -493,6 +495,18 @@ Recorded video and subtitles are in separate files, so the browser will typicall
 multiple files", which must be accepted to get access to the subtitles corresponding to a video recording.
 {% end %}
 
+### System/Application Logs
+
+For debugging purposes, Cockpit keeps track of its internal state changes and errors in JSON-based log files,
+which can be downloaded or deleted from the dev page:
+{{ easy_image(src="system-logs", width=600, center=true) }}
+
+The top right button allows deleting all the old log files as a group.
+
+Downloaded logs can be opened in a standard text editor, and include a sequence of events recorded with a
+[UNIX-style epoch timestamp](https://www.unixtimestamp.com/), together with the event severity level
+(e.g. debug, log, error, etc), and some kind of related message.
+
 ### Alerts
 
 It is possible to select the desired text-to-speech voice, as well as configure which alert severities