Mounting shared filesystems to pods in a Managed Service for Kubernetes® cluster

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Costs

• Compute shared filesystem
• Compute virtual machines that make up a node group

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Prerequisites

1. Make sure you are in a group that has at least the editor role within your tenant; for example, the default editors group. You can check this in the Administration → IAM section of the web console.
2. Install and configure the Nebius AI Cloud CLI. The CLI commands in this article assume that the CLI is properly configured. For example, they omit the ID of the parent project, as it is assumed to be set in the CLI profile.
3. Install kubectl and Helm.
4. Install jq:
   Ubuntu

   macOS

   sudo apt-get install jq
   
5. Create a Managed Service for Kubernetes cluster or choose an existing one, and save its ID to the NB_K8S_CLUSTER_ID environment variable:
   export NB_K8S_CLUSTER_ID=$(nebius mk8s cluster get-by-name \
     --name <cluster_name> --format json | jq -r '.metadata.id')
   

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Steps

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Create a shared filesystem

export NB_FS_ID=$(nebius compute filesystem create \
  --name mk8s-csi-storage \
  --size-gibibytes 256 \
  --type network_ssd \
  --block-size-bytes 4096 \
  --format json | jq -r ".metadata.id")

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Create a node group and mount the filesystem to nodes

1. Create the cloud-init user data that will mount the shared filesystem to nodes:
   export MOUNT_POINT=/mnt/data
   export MOUNT_TAG=csi-storage
   export USER_DATA=$(jq -Rs '.' <<EOF
   runcmd:
     - sudo mkdir -p $MOUNT_POINT
     - sudo mount -t virtiofs $MOUNT_TAG $MOUNT_POINT
     - printf "%s %s virtiofs defaults,nofail 0 2\n" "$MOUNT_TAG" "$MOUNT_POINT" | sudo tee -a /etc/fstab
   EOF
   )
   
   This will mount the filesystem to nodes at /mnt/data as csi-storage. To use another mount point or mount tag, modify the variables.
   Do not omit nofail. If it is not specified and a node cannot find the filesystem on restart (for example, it has been deleted), the node will not boot.
2. Create the partial specification of the node template (other template fields will be set as the Nebius AI Cloud CLI parameters):
   export NB_K8S_NODE_TEMPLATE=$(cat <<EOF
   {
     "spec": {
       "template": {
         "filesystems": [
           {
             "attach_mode": "READ_WRITE",
             "mount_tag": "$MOUNT_TAG",
             "existing_filesystem": {
               "id": "$NB_FS_ID"
             }
           }
         ],
         "cloud_init_user_data": $USER_DATA
       }
     }
   }
   EOF
   )
   
3. Create the node group:
   nebius mk8s node-group create \
     --parent-id $NB_K8S_CLUSTER_ID \
     --name "ng-1" \
     --fixed-node-count 2 \
     --template-resources-platform "cpu-e2" \
     --template-resources-preset "2vcpu-8gb" \
     "$NB_K8S_NODE_TEMPLATE"
   

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Install the CSI driver

1. Pull the driver’s Helm chart:
   helm pull \
     oci://cr.eu-north1.nebius.cloud/mk8s/helm/csi-mounted-fs-path \
     --version 0.1.5
   
2. Install the chart:
   helm upgrade csi-mounted-fs-path ./csi-mounted-fs-path-0.1.5.tgz --install \
     --set dataDir=$MOUNT_POINT/csi-mounted-fs-path-data/
   

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Mount the filesystem to pods

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: csi-pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  storageClassName: csi-mounted-fs-path-sc
---
kind: Pod
apiVersion: v1
metadata:
  name: my-csi-app
spec:
  containers:
  - name: my-csi-app
    image: busybox
    volumeMounts:
      - mountPath: "/data"
        name: my-csi-volume
    command: [ "sleep", "1000000" ]
    securityContext:
      allowPrivilegeEscalation: false
      privileged: false
  volumes:
  - name: my-csi-volume
    persistentVolumeClaim:
      claimName: csi-pvc

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How to delete the created resources

1. Delete the node group:
   • Web console
   • CLI

   1. In the sidebar, go to  Compute → Kubernetes.
   2. Open the page of the required cluster and then go to the Node groups tab.
   3. In the row of the required node group, click  → Delete.
   4. Confirm the node group deletion.

   1. Get the ID of the node group that you want to delete:
      nebius mk8s node-group list --parent-id <cluster_ID>
      
   2. Delete the node group:
      nebius mk8s node-group delete --id <node_group_ID>
      
2. Delete the Compute shared filesystem:
   • Web console
   • CLI

   1. In the sidebar, go to  Storage → Shared filesystems.
   2. Next to the filesystem’s name, click → Delete.
   3. Enter the filesystem’s name and confirm deletion.

   nebius compute filesystem delete --id \
     $(nebius compute filesystem get-by-name \
       --name=<filesystem_name> \
       --format json \
       | jq -r ".metadata.id")
   

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See also

• Mounting disks to pods in a Managed Service for Kubernetes® cluster
• Types of storage volumes in Compute