Why does the Azure NFS fileshare block my Azure Linux Web App from staring normally?

Question

Everything is working fine until this week. After provisioning the entire things onto a new subscription, the Azure Linux Web App mount point config to mount an NFS File Share totally prevents the Azure Linux Web App instance from starting normally. The Web App keeps stuck at Application Error :( and its Log Stream only shows that
```
  Connected!
  
  If you are the application administrator, you can access the ...
```
For more information. I have configured the Azure Linux Web App to mount a Azure NFS File Share, they all sit in the same region which is France Central. In the Storage Account networking settings, I have configured to allow the subnet which is integrated with the Web App and the subnet is also set the deletgation shown as below:

resource "azurerm_subnet" "subnet_1" {
  name                 = azurecaf_name.subnet_1.result
  resource_group_name  = var.resource_group
  virtual_network_name = azurerm_virtual_network.vnet.name
  address_prefixes     = var.subnet_1_address_space
  service_endpoints    = ["Microsoft.Storage"]

  delegation {
    name = "Microsoft.Web.serverFarms"

    service_delegation {
      name = "Microsoft.Web/serverFarms"
      actions = [
        "Microsoft.Network/virtualNetworks/subnets/action"
      ]
    }
  }
}

If anyone has any info about this kind of errors, please feel free to discuss with me.

Answer

Hello [ADMIN] PHAM Khanh,

Greetings! Welcome to Microsoft Q&A Platform.

I understand that your Azure Linux web app stuck at an application error after moving to a new subscription. I would recommended refer this Troubleshoot Azure Files problems in Linux (SMB) (This article lists common problems that are related to Azure Files when you connect from Linux clients. It also provides possible causes and resolutions for these problems)

Azure NFS file shares are supported in all the same regions that support premium file storage.

For the most up-to-date list, see the Premium Files Storage entry on the page for Azure products available by region.

Please check the following to resolve the issue,

Ensure that the NFS share is correctly configured and accessible. Verify that the NFS version is set to 4.1, as Azure Files only supports NFS v4.11.
Confirm that the necessary ports (especially port 2049) are open on the client and that the NFS share is accessible from the new subscription’s network.
Review the mount options used in your configuration. Recommended options include vers=4,minorversion=1, sec=sys, rsize=1048576, and wsize=10485761. Incorrect or missing options might cause the mount to fail.
Confirm that the subnet delegation is correctly set for Microsoft.Web/serverFarms. Ensure that the NFS share is accessible from the web app’s subnet. You might want to test the connectivity using a VM in the same subnet.

If the issue still persists, please share the screen shot of the error message.

reference docs: How to mount an NFS file share

Use Azure Files with Linux

Hope this answer helps! Please let us know if you have any further queries. I’m happy to assist you further.

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Why does the Azure NFS fileshare block my Azure Linux Web App from staring normally?

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