How-to: Mount Pod volumes to the Dapr sidecar

Introduction

The Dapr sidecar can be configured to mount any Kubernetes Volume attached to the application Pod. These Volumes can be accessed by the daprd (sidecar) container in read-only or read-write modes. If a Volume is configured to be mounted but it does not exist in the Pod, Dapr logs a warning and ignores it.

For more information on different types of Volumes, check the Kubernetes documentation.

Configuration

You can set the following annotations in your deployment YAML:

1. dapr.io/volume-mounts: for read-only volume mounts
2. dapr.io/volume-mounts-rw: for read-write volume mounts

These annotations are comma separated pairs of volume-name:path/in/container. Make sure that the corresponding Volumes exist in the Pod spec.

Within the official container images, Dapr runs as a process with user ID (UID) 65532. Make sure that folders and files inside the mounted Volume are writable or readable by user 65532 as appropriate.

Although you can mount a Volume in any folder within the Dapr sidecar container, prevent conflicts and ensure smooth operations going forward by placing all mountpoints within one of these two locations, or in a subfolder within them:

• /mnt is recommended for Volumes containing persistent data that the Dapr sidecar process can read and/or write.
• /tmp is recommended for Volumes containing temporary data, such as scratch disks.

Example

In the example Deployment resource below, my-volume1 and my-volume2 are available inside the sidecar container at /mnt/sample1 and /mnt/sample2 respectively, in read-only mode. my-volume3 is available inside the sidecar container at /tmp/sample3 in read-write mode.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  namespace: default
  labels:
    app: myapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
      annotations:
        dapr.io/enabled: "true"
        dapr.io/app-id: "myapp"
        dapr.io/app-port: "8000"
        dapr.io/volume-mounts: "my-volume1:/mnt/sample1,my-volume2:/mnt/sample2"
        dapr.io/volume-mounts-rw: "my-volume3:/tmp/sample3"
    spec:
      volumes:
        - name: my-volume1
          hostPath:
            path: /sample
        - name: my-volume2
          persistentVolumeClaim:
            claimName: pv-sample
        - name: my-volume3
          emptyDir: {}
...

Examples

Custom secrets storage using local file secret store

Since any type of Kubernetes Volume can be attached to the sidecar, you can use the local file secret store to read secrets from a variety of places. For example, if you have a Network File Share (NFS) server running at 10.201.202.203, with secrets stored at /secrets/stage/secrets.json, you can use that as a secrets storage.

1. Configure the application pod to mount the NFS and attach it to the Dapr sidecar.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
...
spec:
  ...
  template:
    ...
      annotations:
        dapr.io/enabled: "true"
        dapr.io/app-id: "myapp"
        dapr.io/app-port: "8000"
        dapr.io/volume-mounts: "nfs-secrets-vol:/mnt/secrets"
    spec:
      volumes:
        - name: nfs-secrets-vol
          nfs:
            server: 10.201.202.203
            path: /secrets/stage
...

2. Point the local file secret store component to the attached file.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: local-secret-store
spec:
  type: secretstores.local.file
  version: v1
  metadata:
  - name: secretsFile
    value: /mnt/secrets/secrets.json

3. Use the secrets.

GET http://localhost:<daprPort>/v1.0/secrets/local-secret-store/my-secret

Related links

• Dapr Kubernetes pod annotations spec