basics/reforis/diagnostics: Add page about generating diagnostics

Author: ljelinek-cznic

docs/basics/reforis/diagnostics/diagnostics.md

@@ -0,0 +1,44 @@
+---
+board: mox, omnia, 1.x, shield
+competency: novice
+---
+
+# Diagnostics
+
+The _Administration → Diagnostics_ reForis page is intended to get the system
+logs and many other important diagnostics objects that can help us to
+investigate and resolve your problems.
+
+!!! important
+    If you come across any error and it is possible not to reboot the router,
+    please **don’t reboot it** before collecting the logs. All logs are saved in
+    the router memory, and they will be erased if you reboot.
+
+If you just rebooted the router, let it gather some data first. Logs from
+a freshly rebooted router, which have been downloaded before the occurrence
+of the error, usually don’t help us to identify the cause of the error.
+
+## How to get information
+
+Various modules can be included in the generated diagnostics report.
+The modules, which are usually the most interesting, are `disk-full`,
+`messages`, `dns`, `installed`, and `network`. If the nature of the problem
+suggests that other modules could also be useful, you can check them.
+
+![Selection of modules](modules.png)
+
+Then press the _Generate report_ button. The process may take some time.
+When done, you can press _Download_ to download the report. Multiple reports
+may be available, but they don’t persist over reboots.
+
+![Available reports](reports.png)
+
+### If you can’t find the diagnostics
+
+In that case, your router is, for some reason, stuck in some old version
+of the Turris OS. That is the first problem to solve: make sure you have
+updates enabled and your internet connection is working.
+
+!!! tip
+    For more information about getting support from us, please visit
+    the [Troubleshooting → Support](../../support.md) documentation page.

docs/basics/reforis/diagnostics/modules.png

@@ -152,6 +152,7 @@ nav:
           - Administration:
               - Notifications: "basics/reforis/notifications/reforis-notifications.md"
               - Hostname: "basics/reforis/hostname/hostname.md"
+              - Diagnostics: "basics/reforis/diagnostics/diagnostics.md"
           - Factory reset: "basics/reforis/factory-reset/factory-reset.md"
           - Package Management:
               - Updates: "basics/reforis/updates/reforis-updates.md"