Update upgrade documentation

hugo/content/upgrading.md

@@ -10,7 +10,38 @@ categories: ["configuration"]
 doctypes: ["task"]
 ---
 
-## Upgrade the NGINX Agent
+## Upgrade the NGINX Agent from version v2.31.0 or greater
+
+{{< important >}} In version v2.31.0 of the NGINX Agent, the behavior has changed so that the NGINX Agent will automatically restart itself during an upgrade. {{< /important >}}
+
+To upgrade the NGINX Agent, take the following steps:
+
+1. Open an SSH connection to the server where you’ve installed the NGINX Agent and log in.
+
+1. Make a backup copy of the following locations to ensure that you can successfully recover if the upgrade has issues:
+
+    - `/etc/nginx-agent`
+    - `config_dirs` values for any configuration specified in `/etc/nginx-agent/nginx-agent.conf`
+
+1. Install the updated version of the NGINX Agent:
+
+    - CentOS, RHEL, RPM-Based
+
+        ```shell
+        sudo yum -y makecache
+        sudo yum update -y nginx-agent
+        ```
+
+    - Debian, Ubuntu, Deb-Based
+
+        ```shell
+        sudo apt-get update
+        sudo apt-get install -y --only-upgrade nginx-agent -o Dpkg::Options::="--force-confold"
+        ```
+
+
+
+## Upgrade the NGINX Agent from a version less than v2.31.0
 
 To upgrade the NGINX Agent, take the following steps:
 
@@ -47,4 +78,4 @@ To upgrade the NGINX Agent, take the following steps:
 
     ```shell
     sudo systemctl start nginx-agent
-    ```
+    ```