Use storage mounts in Azure Container Apps

Article
03/19/2023

A container app has access to different types of storage. A single app can take advantage of more than one type of storage if necessary.

Storage type	Description	Usage examples
Container file system	Temporary storage scoped to the local container	Writing a local app cache.
Ephemeral storage	Temporary storage scoped to an individual replica	Sharing files between containers in a replica. For instance, the main app container can write log files that are processed by a sidecar container.
Azure Files	Permanent storage	Writing files to a file share to make data accessible by other systems.

Container file system

A container can write to its own file system.

Container file system storage has the following characteristics:

The storage is temporary and disappears when the container is shut down or restarted.
Files written to this storage are only visible to processes running in the current container.
There are no capacity guarantees. The available storage depends on the amount of disk space available in the container.

Ephemeral volume

You can mount an ephemeral, temporary volume that is equivalent to emptyDir in Kubernetes. Ephemeral storage is scoped to a single replica.

Ephemeral storage has the following characteristics:

Files are persisted for the lifetime of the replica.
- If a container in a replica restarts, the files in the volume remain.
Any containers in the replica can mount the same volume.
A container can mount multiple ephemeral volumes.
The available storage depends on the total amount of vCPUs allocated to the replica.

vCPUs Ephemeral storage

0.25 or lower 1 GiB

0.5 or lower 2 GiB

1 or lower 4 GiB

Over 1 8 GiB

vCPUs	Ephemeral storage
0.25 or lower	1 GiB
0.5 or lower	2 GiB
1 or lower	4 GiB
Over 1	8 GiB

To configure ephemeral storage, first define an EmptyDir volume in the revision. Then define a volume mount in one or more containers in the revision.

Prerequisites

Requirement	Instructions
Azure account	If you don't have one, create an account for free.
Azure Container Apps environment	Create a container apps environment.

Configuration

When configuring ephemeral storage using the Azure CLI, you must use a YAML definition to create or update your container app.

To update an existing container app to use ephemeral storage, export your app's specification to a YAML file named app.yaml.
```
az containerapp show -n <APP_NAME> -g <RESOURCE_GROUP_NAME> -o yaml > app.yaml
```
Make the following changes to your container app specification.
- Add a volumes array to the template section of your container app definition and define a volume. If you already have a volumes array, add a new volume to the array.
  - The name is an identifier for the volume.
  - Use EmptyDir as the storageType.
- For each container in the template that you want to mount the ephemeral volume, define a volume mount in the volumeMounts array of the container definition.
  - The volumeName is the name defined in the volumes array.
  - The mountPath is the path in the container to mount the volume.
```
properties:
  managedEnvironmentId: /subscriptions/<SUBSCRIPTION_ID>/resourceGroups/<RESOURCE_GROUP_NAME>/providers/Microsoft.App/managedEnvironments/<ENVIRONMENT_NAME>
  configuration:
    activeRevisionsMode: Single
  template:
    containers:
    - image: <IMAGE_NAME>
      name: my-container
      volumeMounts:
      - mountPath: /myempty
        volumeName: myempty
    volumes:
    - name: myempty
      storageType: EmptyDir
```

Update your container app using the YAML file.

az containerapp update --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> \
    --yaml app.yaml

See the YAML specification for a full example.

To create an ephemeral volume and mount it in a container, make the following changes to the container apps resource in an ARM template:

Add a volumes array to the template section of your container app definition and define a volume. If you already have a volumes array, add a new volume to the array.
- The name is an identifier for the volume.
- Use EmptyDir as the storageType.
For each container in the template that you want to mount temporary storage, define a volume mount in the volumeMounts array of the container definition.
- The volumeName is the name defined in the volumes array.
- The mountPath is the path in the container to mount the volume.

Example ARM template snippet:

{
  "apiVersion": "2022-03-01",
  "type": "Microsoft.App/containerApps",
  "name": "[parameters('containerappName')]",
  "location": "[parameters('location')]",
  "properties": {

    ...

    "template": {
      "revisionSuffix": "myrevision",
      "containers": [
        {
          "name": "main",
          "image": "[parameters('container_image')]",
          "resources": {
            "cpu": 0.5,
            "memory": "1Gi"
          },
          "volumeMounts": [
            {
              "mountPath": "/myempty",
              "volumeName": "myempty"
            }
          ]
        }
      ],
      "scale": {
        "minReplicas": 1,
        "maxReplicas": 3
      },
      "volumes": [
        {
          "name": "myempty",
          "storageType": "EmptyDir"
        }
      ]
    }
  }
}

See the ARM template API specification for a full example.

To create an ephemeral volume and mount it in a container, deploy a new revision of your container app using the Azure portal.

In the Azure portal, navigate to your container app.
Select Revision management in the left menu.
Select Create new revision.
Select the container where you want to mount the volume.
In the Edit a container context pane, select the Volume mounts tab.
Under the Ephemeral storage section, create a new volume with the following information.
- Volume name: A name for the ephemeral volume.
- Mount path: The absolute path in the container to mount the volume.
Select Save to save changes and exit the context pane.
Select Create to create the new revision.

Azure Files volume

You can mount a file share from Azure Files as a volume in a container.

Azure Files storage has the following characteristics:

Files written under the mount location are persisted to the file share.
Files in the share are available via the mount location.
Multiple containers can mount the same file share, including ones that are in another replica, revision, or container app.
All containers that mount the share can access files written by any other container or method.
More than one Azure Files volume can be mounted in a single container.

To enable Azure Files storage in your container, you need to set up your container in the following ways:

Create a storage definition in the Container Apps environment.
Define a volume of type AzureFile in a revision.
Define a volume mount in one or more containers in the revision.

Prerequisites

Requirement	Instructions
Azure account	If you don't have one, create an account for free.
Azure Storage account	Create a storage account.
Azure Container Apps environment	Create a container apps environment.

Configuration

When configuring a container app to mount an Azure Files volume using the Azure CLI, you must use a YAML definition to create or update your container app.

For a step-by-step tutorial, refer to Create an Azure Files storage mount in Azure Container Apps.

Add a storage definition to your Container Apps environment.
```
az containerapp env storage set --name my-env --resource-group my-group \
    --storage-name mystorage \
    --azure-file-account-name <STORAGE_ACCOUNT_NAME> \
    --azure-file-account-key <STORAGE_ACCOUNT_KEY> \
    --azure-file-share-name <STORAGE_SHARE_NAME> \
    --access-mode ReadWrite
```
Replace <STORAGE_ACCOUNT_NAME> and <STORAGE_ACCOUNT_KEY> with the name and key of your storage account. Replace <STORAGE_SHARE_NAME> with the name of the file share in the storage account.

Valid values for --access-mode are ReadWrite and ReadOnly.
To update an existing container app to mount a file share, export your app's specification to a YAML file named app.yaml.
```
az containerapp show -n <APP_NAME> -g <RESOURCE_GROUP_NAME> -o yaml > app.yaml
```
Make the following changes to your container app specification.
- Add a volumes array to the template section of your container app definition and define a volume. If you already have a volumes array, add a new volume to the array.
  - The name is an identifier for the volume.
  - For storageType, use AzureFile.
  - For storageName, use the name of the storage you defined in the environment.
- For each container in the template that you want to mount Azure Files storage, define a volume mount in the volumeMounts array of the container definition.
  - The volumeName is the name defined in the volumes array.
  - The mountPath is the path in the container to mount the volume.
```
properties:
  managedEnvironmentId: /subscriptions/<SUBSCRIPTION_ID>/resourceGroups/<RESOURCE_GROUP_NAME>/providers/Microsoft.App/managedEnvironments/<ENVIRONMENT_NAME>
  configuration:
  template:
    containers:
    - image: <IMAGE_NAME>
      name: my-container
      volumeMounts:
      - volumeName: azure-files-volume
        mountPath: /my-files
    volumes:
    - name: azure-files-volume
      storageType: AzureFile
      storageName: mystorage
```

Update your container app using the YAML file.

az containerapp update --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> \
    --yaml app.yaml

See the YAML specification for a full example.

The following ARM template snippets demonstrate how to add an Azure Files share to a Container Apps environment and use it in a container app.

Add a storages child resource to the Container Apps environment.

{
  "type": "Microsoft.App/managedEnvironments",
  "apiVersion": "2022-03-01",
  "name": "[parameters('environment_name')]",
  "location": "[parameters('location')]",
  "properties": {
    "daprAIInstrumentationKey": "[parameters('dapr_ai_instrumentation_key')]",
    "appLogsConfiguration": {
      "destination": "log-analytics",
      "logAnalyticsConfiguration": {
        "customerId": "[parameters('log_analytics_customer_id')]",
        "sharedKey": "[parameters('log_analytics_shared_key')]"
      }
    }
  },
  "resources": [
    {
      "type": "storages",
      "name": "myazurefiles",
      "apiVersion": "2022-03-01",
      "dependsOn": [
        "[resourceId('Microsoft.App/managedEnvironments', parameters('environment_name'))]"
      ],
      "properties": {
        "azureFile": {
          "accountName": "[parameters('storage_account_name')]",
          "accountKey": "[parameters('storage_account_key')]",
          "shareName": "[parameters('storage_share_name')]",
          "accessMode": "ReadWrite"
        }
      }
    }
  ]
}

Update the container app resource to add a volume and volume mount.

{
  "apiVersion": "2022-03-01",
  "type": "Microsoft.App/containerApps",
  "name": "[parameters('containerappName')]",
  "location": "[parameters('location')]",
  "properties": {

    ...

    "template": {
      "revisionSuffix": "myrevision",
      "containers": [
        {
          "name": "main",
          "image": "[parameters('container_image')]",
          "resources": {
            "cpu": 0.5,
            "memory": "1Gi"
          },
          "volumeMounts": [
            {
              "mountPath": "/myfiles",
              "volumeName": "azure-files-volume"
            }
          ]
        }
      ],
      "scale": {
        "minReplicas": 1,
        "maxReplicas": 3
      },
      "volumes": [
        {
          "name": "azure-files-volume",
          "storageType": "AzureFile",
          "storageName": "myazurefiles"
        }
      ]
    }
  }
}

Add a volumes array to the template section of your container app definition and define a volume. If you already have a volumes array, add a new volume to the array.
- The name is an identifier for the volume.
- For storageType, use AzureFile.
- For storageName, use the name of the storage you defined in the environment.
For each container in the template that you want to mount Azure Files storage, define a volume mount in the volumeMounts array of the container definition.
- The volumeName is the name defined in the volumes array.
- The mountPath is the path in the container to mount the volume.

See the ARM template API specification for a full example.

To configure a volume mount for Azure Files storage in the Azure portal, add a file share to your Container Apps environment and then add a volume mount to your container app by creating a new revision.

In the Azure portal, navigate to your Container Apps environment.
Select Azure Files from the left menu.
Select Add.
In the Add file share context menu, enter the following information:
- Name: A name for the file share.
- Storage account name: The name of the storage account that contains the file share.
- Storage account key: The access key for the storage account.
- File share: The name of the file share.
- Access mode: The access mode for the file share. Valid values are "Read/Write" and "Read only".
Select Add to exit the context pane.
Select Save to commit the changes.
Navigate to your container app.
Select Revision management from the left menu.
Select Create new revision.
Select the container that you want to mount the volume in.
In the Edit a container context pane, select the Volume mounts tab.
Under the File shares section, create a new volume with the following information.
- File share name: The file share you added.
- Mount path: The absolute path in the container to mount the volume.
Select Save to save changes and exit the context pane.
Select Create to create the new revision.

Use storage mounts in Azure Container Apps

Container file system

Ephemeral volume

Prerequisites

Configuration

Azure Files volume

Prerequisites

Configuration

Feedback

Additional resources

Additional resources