OS Patching Procedure for Minimal Downtime

To minimize application downtime in environments spanning multiple data centers, it is recommended to perform a rolling update. This process involves stopping the application on one node at a time, applying the OS patches, and then restarting the node before moving to the next one.

Log in to the installer node and navigate to <appviewx installer directory>/scripts.
Stop the application on the node - Before applying the patch, stop the application on the specific node. This ensures that the node is not running any critical services during the patching process.
Run the following command to stop the application:
```
./appviewx.sh --stop <node_name>
```
Note: Replace <node_name> with the actual name of the node you are stopping.
Apply the OS patch/security update - Once the application is stopped, proceed with updating the operating system. Run the following commands to apply the necessary patches:
Run the following command to stop the application:
```
sudo apt update -y
```
```
sudo apt upgrade -y
```
This will update the package lists and apply all available OS security patches.
Reboot the node - After the patching is complete, reboot the node to ensure that all changes are applied properly.
```
sudo reboot
```
Start the application on the node - After the node has rebooted, start the application back up using the following command:
```
./appviewx.sh --start <node_name>
```
Note: Replace <node_name> with the actual name of the node.
Repeat for the remaining nodes in the data center - Repeat the above steps for all the nodes in the first data center. Ensure that each node is patched one at a time to avoid any application downtime within the data center.
Move to the next data center - Once all nodes in the first data center have been patched and verified to be working, proceed to the second data center and follow the same steps for each node.