Merge pull request #200391 from nabeelp/docs-editor/functions-recover-storage-acco-1654267190

Adding guidance around Linux container version misconfiguration

Author: GitHubber17

articles/azure-functions/functions-recover-storage-account.md

@@ -31,10 +31,10 @@ In the preceding step, if you can't find a storage account connection string, it
 ### Required application settings
 
 * Required:
-    * [`AzureWebJobsStorage`](./functions-app-settings.md#azurewebjobsstorage)
+  * [`AzureWebJobsStorage`](./functions-app-settings.md#azurewebjobsstorage)
 * Required for Premium plan functions:
-    * [`WEBSITE_CONTENTAZUREFILECONNECTIONSTRING`](./functions-app-settings.md)
-    * [`WEBSITE_CONTENTSHARE`](./functions-app-settings.md)
+  * [`WEBSITE_CONTENTAZUREFILECONNECTIONSTRING`](./functions-app-settings.md)
+  * [`WEBSITE_CONTENTSHARE`](./functions-app-settings.md)
 
 For more information, see [App settings reference for Azure Functions](./functions-app-settings.md).
 
@@ -55,6 +55,7 @@ Your function app must be able to access the storage account. Common issues that
 * The function app is deployed to your App Service Environment (ASE) without the correct network rules to allow traffic to and from the storage account.
 
 * The storage account firewall is enabled and not configured to allow traffic to and from functions. For more information, see [Configure Azure Storage firewalls and virtual networks](../storage/common/storage-network-security.md?toc=%2fazure%2fstorage%2ffiles%2ftoc.json).
+
 * Verify that the `allowSharedKeyAccess` setting is set to `true` which is its default value. For more information, see [Prevent Shared Key authorization for an Azure Storage account](../storage/common/shared-key-authorization-prevent.md?tabs=portal#verify-that-shared-key-access-is-not-allowed). 
 
 ## Daily execution quota is full
@@ -63,7 +64,7 @@ If you have a daily execution quota configured, your function app is temporarily
 
 To verify the quota in the [Azure portal](https://portal.azure.com), select **Platform Features** > **Function App Settings** in your function app. If you're over the **Daily Usage Quota** you've set, the following message is displayed:
 
-  > "The Function App has reached daily usage quota and has been stopped until the next 24 hours time frame."
+> "The Function App has reached daily usage quota and has been stopped until the next 24 hours time frame."
 
 To resolve this issue, remove or increase the daily quota, and then restart your app. Otherwise, the execution of your app is blocked until the next day.
 
@@ -78,16 +79,33 @@ Your function app might be unreachable for either of the following reasons:
 The Azure portal makes calls directly to the running app to fetch the list of functions, and it makes HTTP calls to the Kudu endpoint. Platform-level settings under the **Platform Features** tab are still available.
 
 To verify your ASE configuration:
+
 1. Go to the network security group (NSG) of the subnet where the ASE resides.
 1. Validate the inbound rules to allow traffic that's coming from the public IP of the computer where you're accessing the application. 
-   
+
 You can also use the portal from a computer that's connected to the virtual network that's running your app or to a virtual machine that's running in your virtual network. 
 
 For more information about inbound rule configuration, see the "Network Security Groups" section of [Networking considerations for an App Service Environment](../app-service/environment/network-info.md#network-security-groups).
 
+## Container image unavailable (Linux)
+
+For Linux function apps that run from a container, the "Azure Functions runtime is unreachable" error can occur when the container image being referenced is unavailable or fails to start correctly.
+
+To confirm that the error is caused for this reason:
+
+1. Navigate to the Kudu endpoint for the function app, which is located at `https://scm.<FUNCTION_APP>.azurewebsites.net`, where `<FUNCTION_APP>` is the name of your app.
+
+1. Download the Docker logs ZIP file and review them locally, or review the docker logs from within Kudu.
+
+1. Check for any errors in the logs that would indicate that the container is unable to start successfully.
+
+Any such error would need to be remedied for the function to work correctly.
+
+When the container image can't be found, you should see a `manifest unknown` error in the Docker logs.  In this case, you can use the Azure CLI commands documented at [How to target Azure Functions runtime versions](set-runtime-version.md?tabs=azurecli) to change the container image being reference. If you've deployed a custom container image, you need to fix the image and redeploy the updated version to the referenced registry.
+
 ## Next steps
 
 Learn about monitoring your function apps:
-
 > [!div class="nextstepaction"]
-> [Monitor Azure Functions](functions-monitoring.md)
+> [Monitor Azure Functions](functions-monitoring.md)
+