How to configure Azure Web App Sidecar to use Azure File Share as Container Volume Mounts ?

Question

Good afternoon, colleagues.

I am taking my first steps in learning Azure, so I am asking for help.

I need to deploy an application with three containers (NGinx as a reverse proxy, ASP.NET Web API as a backend, Angular as a frontend) in Azure Web App. The ASP.NET Web API container must be able to store static files in Azure File Share. And I need to access these files through Azure File Share.

First I planned to use Docker Compose to deploy all containers at once. Docker Compose allows to configure the Docker Volume of a container in File Share thanks to Path Mapping (App Service > Configuration > Path Mapping). Information about this is available on the internet.

But it turns out that Docker Compose is being phased out and will be removed soon, so I'm trying to do everything on Sidecar.

Unfortunately, I cannot find any information or examples on how to configure Path Mapping for Sidecar.

The article "Configure sidecars in Azure App Service" - https://learn.microsoft.com/en-us/azure/app-service/configure-sidecar contains information about volume mounts, but there is no word about Path Mapping to File Share and using this mapping in Sidecar.

How to add the created Path Mapping when configuring Sidecar?

I am new at cloud technologies and DevOps, so I hope for an answer without using Azure CLI.

Answer 1

Hi @Prykhodko, Oleksii (ext) (RC-UA DI S SAC),
When using the new Sidecar container model in Azure App Service, mounting an Azure File Share is configured differently than in Docker Compose–based multi-container deployments. In Sidecar architecture, you must first create an Azure Storage mount at the Web App level by navigating to Configuration Path mappings and adding the Azure Files share. This step mounts the file share to the underlying App Service host. After the storage mount is created, you then attach it to the required container (for example, the ASP.NET backend container) by configuring the Volume mounts section in the container settings. Here, the Volume sub path represents the logical shared directory from the previously created storage mount, and the Container mount path defines the folder inside the container where the storage will be accessible for read/write operations. Containers that use the same volume sub path can share files through this mounted Azure File Share. This approach replaces the earlier Docker Compose volume mapping behavior and is the currently supported and documented method for persistent shared storage in multi-container (Sidecar) Azure Web App deployments.
https://learn.microsoft.com/en-us/azure/app-service/configure-connect-to-azure-storage?tabs=basic%2Cportal&pivots=container-linux
https://learn.microsoft.com/en-us/azure/app-service/configure-sidecar
Let me know if you have any further assistances needed.

Answer 2

Path mappings (Azure Storage mounts) and sidecar volume mounts are two different mechanisms and are not directly connected in App Service.

For sidecar-enabled Linux custom container apps:

1. Storage mounts configured under Configuration → Path mappings (Azure Files / Blob) are not used by the sidecar volume‑mount feature.
2. Sidecar volume mounts, as documented in the sidecar article, are ephemeral volumes shared only between containers in the same Web App. They are backed by the App Service /home storage and are not a way to mount Azure File Share into a sidecar.
3. The Volume sub path and Container mount path fields in the Add container (sidecar) UI only define logical directories inside the App Service storage space that containers can share with each other. They do not accept or reference an Azure File Share path or a Path Mapping name.

Therefore, with the capabilities described in the sidecar documentation, a sidecar container cannot be configured to use an Azure File Share via Path Mapping; sidecar volume mounts can only share non‑persistent storage between the main container and sidecars.

If the ASP.NET Web API must write to Azure Files and those files must also be accessible directly via Azure File Share, use one of these supported approaches instead of sidecar volume mounts:

• Configure a regular Azure Storage mount (Path mapping) for the main container and have the Web API write to that mount.
• Or have the Web API use the Azure Storage SDK/REST API to read/write directly to Azure Files, without relying on sidecar volume mounts.

---

References:

• Configure sidecars in Azure App Service
• Sidecars in Azure App Service
• Tutorial: Configure a sidecar container for a custom container app
• Tutorial: Create an Azure Files volume mount in Azure Container Apps