modified: README.md

README.md

@@ -57,6 +57,8 @@ Kubernetes is an open‑source platform that automates the deployment, scaling,
     - [troubleshooting](#troubleshooting)
 - [host cli](#host-cli)
   - [host cli - check port usage](#host-cli---check-port-usage)
+- [cert-manager](#cert-manager)
+
 
 ## Namespaces
 
@@ -772,3 +774,15 @@ systemctl restart k3s-agent
 # example: port 32329
 ss -ltnp | grep 32329
 ```
+
+## cert-manager
+
+clear stale ACME challenges and orders created before DNS fixes.  
+These objects are temporary and safe to delete — they do NOT remove or affect existing valid certificates.  
+After cleanup, cert-manager automatically recreates fresh challenges using the corrected DNS configuration.
+
+``` bash
+kubectl delete challenge -A --all
+kubectl delete order -A --all
+
+```