cmd/syncthing: Explain corruption panics (fixes #3689)

cmd/syncthing/monitor.go

@@ -202,8 +202,24 @@ func copyStderr(stderr io.Reader, dst io.Writer) {
 				}
 
 				l.Warnf("Panic detected, writing to \"%s\"", panicFd.Name())
-				l.Warnln("Please check for existing issues with similar panic message at https://github.com/syncthing/syncthing/issues/")
+				if strings.Contains(line, "leveldb") && strings.Contains(line, "corrupt") {
-				l.Warnln("If no issue with similar panic message exists, please create a new issue with the panic log attached")
+					l.Warnln(`
+*********************************************************************************
+* Crash due to corrupt database.                                                *
+*                                                                               *
+* This crash usually occurs due to one of the following reasons:                *
+*  - Syncthing being stopped abruptly (killed/loss of power)                    *
+*  - Bad hardware (memory/disk issues)                                          *
+*  - Software that affects disk writes (SSD caching software and simillar)      *
+*                                                                               *
+* Please see the following URL for instructions on how to recover:              *
+*   https://docs.syncthing.net/users/faq.html#my-syncthing-database-is-corrupt  *
+*********************************************************************************
+`)
+				} else {
+					l.Warnln("Please check for existing issues with similar panic message at https://github.com/syncthing/syncthing/issues/")
+					l.Warnln("If no issue with similar panic message exists, please create a new issue with the panic log attached")
+				}
 
 				stdoutMut.Lock()
 				for _, line := range stdoutFirstLines {