Custom Script Extension failing on Virtual Scale Set upgrade - linux

Question

I have created an Azure virtual scaleset with Linux VMs. I have to run Azure CLI commands via release pipelines on these VMs so I am trying to install a Azure CLI using Custom Extensions so that every time a new VM is up CLI is installed on the VM.
I have created a .sh file with below command on blob storage :
curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash
I ran below command on from the CLI to deploy the custom extension :
az vmss extension set --vmss-name <VMSS Name> --resource-group <Resource Group> --name CustomScript --version 2.0 --publisher Microsoft.Azure.Extensions --settings '{"FileUris": ["https://<Blobscriptpath>/preinstallscript.sh"],"commandToExecute": "bash /preinstallscript.sh"}'
This command is installing the extension and I can see that on Azure but when I am upgrading the VM instance I am getting below error:
"Failed to upgrade virtual machine instance ''. Error: Multiple VM extensions failed to be provisioned on the VM. Please see the VM extension instance view for other failures. The first extension failed due to the error: VM has reported a failure when processing extension 'CustomScript'. Error message: "Enable failed: failed to get configuration: json validation error: invalid public settings JSON: FileUris: Additional property FileUris is not allowed""
Below are the images from Azure Portal showing the Extension:
Please suggest if I am missing something.

Answer 1

According to the error message, Additional property FileUris is not allowed, you should use fileUris instead of FileUris. Read the Property values.
Also, If the blob is not public, you need to provide the storage account name and key to access the blob. For example, you can provide a .sh file on the blob storage.
#!/bin/bash
curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash
and deploy the custom extension with CLI.
az vmss extension set --vmss-name <VMSS Name> --resource-group <Resource Group> --name CustomScript --version 2.0 --publisher Microsoft.Azure.Extensions --settings '{"fileUris": ["https://xxx.blob.core.windows.net/shscripts/preinstallscript.sh"],"commandToExecute": "sh preinstallscript.sh"}'
Edit
After installing the VMSS, you can upgrade the VMSS instance to take this script effect.