document ins doctor

Author: paperbenni

faq.md

@@ -8,6 +8,29 @@ we have an active and friendly [community](https://instantos.io/support) to supp
 The [Discord channel](https://dsc.gg/instantos) is usually the quickest and most active way to get information.
 
 
+## Troubleshooting system issues
+
+instantOS includes a diagnostic tool to check and fix common system problems:
+
+```bash
+# Run all health checks
+ins doctor
+
+# List available checks
+ins doctor list
+
+# Run a specific check
+ins doctor run <check-name>
+
+# Fix all fixable issues
+ins doctor fix --all
+
+# Interactively choose which fixes to apply
+ins doctor fix --choose
+```
+
+Checks include: network connectivity, locale, pending updates, disk health, swap status, display configuration, and more.
+
 
 ## Does it use its own repos