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CSI RBD Plugin

The RBD CSI plugin is able to provision new RBD images and attach and mount those to workloads.

Building

CSI plugin can be compiled in a form of a binary file or in a form of a Docker image. When compiled as a binary file, the result is stored in _output/ directory with the name cephcsi. When compiled as an image, it's stored in the local Docker image store with name cephcsi.

Building binary:

make cephcsi

Building Docker image:

make image-cephcsi

Configuration

Available command line arguments:

Option Default value Description
--endpoint unix:///tmp/csi.sock CSI endpoint, must be a UNIX socket
--csi-addons-endpoint unix:///tmp/csi-addons.sock CSI-Addons endpoint, must be a UNIX socket
--drivername rbd.csi.ceph.com Name of the driver (Kubernetes: provisioner field in StorageClass must correspond to this value)
--nodeid empty This node's ID
--type empty Driver type: [rbd/cephfs]. If the driver type is set to rbd it will act as a rbd plugin or if it's set to cephfs will act as a cephfs plugin
--instanceid "default" Unique ID distinguishing this instance of Ceph CSI among other instances, when sharing Ceph clusters across CSI instances for provisioning
--pidlimit 0 Configure the PID limit in cgroups. The container runtime can restrict the number of processes/tasks which can cause problems while provisioning (or deleting) a large number of volumes. A value of -1 configures the limit to the maximum, 0 does not configure limits at all.
--metricsport 8080 TCP port for liveness metrics requests
--metricspath "/metrics" Path of prometheus endpoint where metrics will be available
--enablegrpcmetrics false [Deprecated] Enable grpc metrics collection and start prometheus server
--polltime "60s" Time interval in between each poll
--timeout "3s" Probe timeout in seconds
--histogramoption 0.5,2,6 [Deprecated] Histogram option for grpc metrics, should be comma separated value (ex:= "0.5,2,6" where start=0.5 factor=2, count=6)
--domainlabels empty Kubernetes node labels to use as CSI domain labels for topology aware provisioning, should be a comma separated value (ex:= "failure-domain/region,failure-domain/zone")
--rbdhardmaxclonedepth 8 Hard limit for maximum number of nested volume clones that are taken before a flatten occurs
--rbdsoftmaxclonedepth 4 Soft limit for maximum number of nested volume clones that are taken before a flatten occurs
--skipforceflatten false skip image flattening on kernel < 5.2 which support mapping of rbd images which has the deep-flatten feature
--maxsnapshotsonimage 450 Maximum number of snapshots allowed on rbd image without flattening

Available volume parameters:

Parameter Required Description
clusterID yes String representing a Ceph cluster, must be unique across all Ceph clusters in use for provisioning, cannot be greater than 36 bytes in length, and should remain immutable for the lifetime of the Ceph cluster in use
pool yes Ceph pool into which the RBD image shall be created
dataPool no Ceph pool used for the data of the RBD images.
volumeNamePrefix no Prefix to use for naming RBD images (defaults to csi-vol-).
snapshotNamePrefix no Prefix to use for naming RBD snapshot images (defaults to csi-snap-).
imageFeatures yes RBD image features. CSI RBD currently supports layering, journaling, exclusive-lock, object-map, fast-diff features. If journaling is enabled, must enable exclusive-lock too. See man pages Note that the required support for object-map and fast-diff were added in 5.3 and journaling does not have KRBD support yet. deep-flatten is added for cloned images.
tryOtherMounters no Specifies whether to try other mounters in case if the current mounter fails to mount the rbd image for any reason
mapOptions no Map options to use when mapping rbd image. See krbd and nbd options.
unmapOptions no Unmap options to use when unmapping rbd image. See krbd and nbd options.
csi.storage.k8s.io/provisioner-secret-name, csi.storage.k8s.io/node-stage-secret-name yes (for Kubernetes) name of the Kubernetes Secret object containing Ceph client credentials. Both parameters should have the same value
csi.storage.k8s.io/provisioner-secret-namespace, csi.storage.k8s.io/node-stage-secret-namespace yes (for Kubernetes) namespaces of the above Secret objects
mounter no if set to rbd-nbd, use rbd-nbd on nodes that have rbd-nbd and nbd kernel modules to map rbd images
encrypted no disabled by default, use "true" to enable LUKS encryption on PVC and "false" to disable it. Do not change for existing storageclasses
encryptionKMSID no required if encryption is enabled and a kms is used to store passphrases
thickProvision no if set to "true", newly created RBD images will be completely allocated by writing zeros to it (DEPRECATED: recommended alternative solution is to use accounting/quotas for created volumes)

NOTE: An accompanying CSI configuration file, needs to be provided to the running pods. Refer to Creating CSI configuration for more information.

NOTE: A suggested way to populate and retain uniqueness of the clusterID is to use the output of ceph fsid of the Ceph cluster to be used for provisioning.

Required secrets:

User credentials, with required access to the pool being used in the storage class, is required for provisioning new RBD images.

Deployment with Kubernetes

Requires Kubernetes 1.14+

Use the rbd templates

Your Kubernetes cluster must allow privileged pods (i.e. --allow-privileged flag must be set to true for both the API server and the kubelet). Moreover, as stated in the mount propagation docs, the Docker daemon of the cluster nodes must allow shared mounts.

YAML manifests are located in deploy/rbd/kubernetes.

Deploy RBACs for sidecar containers and node plugins:

kubectl create -f csi-provisioner-rbac.yaml
kubectl create -f csi-nodeplugin-rbac.yaml

Those manifests deploy service accounts, cluster roles and cluster role bindings. These are shared for both RBD and CephFS CSI plugins, as they require the same permissions.

Deploy PodSecurityPolicy resources for sidecar containers and node plugins:

NOTE: These manifests are required only if PodSecurityPolicy admission controller is active on your cluster.

kubectl create -f csi-provisioner-psp.yaml
kubectl create -f csi-nodeplugin-psp.yaml

Deploy ConfigMap for CSI plugins:

kubectl create -f csi-config-map.yaml

The configmap deploys an empty CSI configuration that is mounted as a volume within the Ceph CSI plugin pods. To add a specific Ceph clusters configuration details, refer to Creating CSI configuration for RBD based provisioning for more information.

Deploy Ceph configuration ConfigMap for CSI pods:

kubectl create -f ../example/ceph-config.yaml

Deploy CSI sidecar containers:

kubectl create -f csi-rbdplugin-provisioner.yaml

Deploys deployment of provision which includes external-provisioner ,external-attacher,csi-snapshotter sidecar containers and CSI RBD plugin.

Deploy RBD CSI driver:

kubectl create -f csi-rbdplugin.yaml

Deploys a daemon set with two containers: CSI node-driver-registrar and the CSI RBD driver.

NOTE: In case you want to use a different release version, replace canary with the release version in the provisioner and nodeplugin YAMLs.

# for stable functionality replace canary with latest release version
    image: quay.io/cephcsi/cephcsi:canary

Check the release version here.

Verifying the deployment in Kubernetes

After successfully completing the steps above, you should see output similar to this:

$ kubectl get all
NAME                              READY     STATUS    RESTARTS   AGE
pod/csi-rbdplugin-fptqr           3/3       Running   0          21s
pod/csi-rbdplugin-provisioner-0   5/5       Running   0          22s

NAME                                TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)     AGE
service/csi-rbdplugin-provisioner   ClusterIP   10.104.2.130   <none>        8080/TCP   23s
...

Once the CSI plugin configuration is updated with details from a Ceph cluster of choice, you can try deploying a demo pod from examples/rbd using the instructions provided to test the deployment further.

Deployment with Helm

The same requirements from the Kubernetes section apply here, i.e. Kubernetes version, privileged flag and shared mounts.

The Helm chart is located in charts/ceph-csi-rbd.

Deploy Helm Chart:

See the Helm chart readme for installation instructions.

Encryption for RBD volumes

Enabling encryption on volumes created without encryption is not supported

Enabling encryption for storage class that has PVs created without encryption is not supported

Volumes provisioned with Ceph RBD do not have encryption by default. It is possible to encrypt them with ceph-csi by using LUKS encryption.

Life-cycle for encrypted volumes

Create volume:

  • create volume request received
  • volume requested to be created in Ceph
  • new passphrase is generated and stored in selected KMS if KMS is in use
  • encrypted state "encryptionPrepared" is saved in image-meta in Ceph

Attach volume:

  • attach volume request received
  • volume is attached to provisioner container
  • on first time attachment (no file system on the attached device, checked with blkid)
    • passphrase is retrieved from selected KMS if KMS is in use
    • device is encrypted with LUKS using a passphrase from K8s Secret or KMS
    • image-meta updated to "encrypted" in Ceph
  • passphrase is retrieved from selected KMS if KMS is in use
  • device is open and device path is changed to use a mapper device
  • mapper device is used instead of original one with usual workflow

Detach volume:

  • mapper device closed and device path changed to original volume path
  • volume is detached as usual
  • passphrase removed from KMS if needed (with failures ignored)

Encryption configuration

To encrypt rbd volumes with LUKS you need to set encryption passphrase in secrets under encryptionPassphrase key and switch encrypted option in StorageClass to "true". This is not supported for storage classes that already have PVs provisioned. The node-stage-secret-name and the provisioner-secret-name should carry this key and value for encryption to work.

To use different passphrase you need to have different storage classes and point to a different K8s secrets csi.storage.k8s.io/node-stage-secret-name and csi.storage.k8s.io/provisioner-secret-name which carry new passphrase value for encryptionPassphrase key in these secrets.

Encryption metadata configuration

CephCSI can generate unique passphrase (DEK Data-Encryption-Key) for each volume to be used to encrypt/decrypt data. The passphrase (DEK) is encrypted by encryptionPassphrase (KEK Key-Encryption-Key) and stored in the image metadata of the volume.

To encrypt rbd volumes with metadata encryption, users need to set encrypted: "true" and encryptionKMSID to a unique identifier in storageclass. This unique identifier should be similar to the examples. The configuration must include "encryptionKMSType": "metadata". The encryptionPassphrase is fetched based on the following conditions:

  • if "secretName" key is specified, encryptionPassphrase is fetched from this secret and "secretNamespace" value is used for namespace if specified else Tenant/Kubernetes namespace (i.e., namespace where the PVC was created) is used.
  • if "secretName" key is not specified, encryptionPassphrase is fetched from storageclass secrets csi.storage.k8s.io/provisioner-secret-namespace / csi.storage.k8s.io/provisioner-secret-name and csi.storage.k8s.io/node-stage-secret-namespace / csi.storage.k8s.io/node-stage-secret-name similar to the previous Encryption Configuration.

Encryption KMS configuration

To further improve security robustness it is possible to use unique passphrases generated for each volume and stored in a Key Management System (KMS). Currently HashiCorp Vault is the only KMS supported.

There are two options to use Hashicorp Vault as a KMS:

  1. with Kubernetes ServiceAccount
  2. with a Vault Token per Tenant (a Kubernetes Namespace)

To use Vault as KMS set encryptionKMSID to a unique identifier for Vault configuration. You will also need to create vault configuration similar to the example and use same encryptionKMSID.

To use the Kubernetes ServiceAccount to access Vault, the configuration must include encryptionKMSType: "vault". If Tenants are expected to place their Vault Token in a Kubernetes Secret in their Namespace, set encryptionKMSType: "vaulttokens".

In order for ceph-csi to be able to access the configuration you will need to have it mounted to csi-rbdplugin containers in both daemonset (so kms client can be instantiated to encrypt/decrypt volumes) and deployment pods (so kms client can be instantiated to delete passphrase on volume delete) ceph-csi-encryption-kms-config configmap.

Note: kms configuration must be a map of string values only (map[string]string) so for numerical and boolean values make sure to put quotes around.

When the Tenants need to provide their own Vault Token, they will need to place it in a Kubernetes Secret (by default) called ceph-csi-kms-token, where the Vault Token is stored in the token key as shown in the example.

Configuring HashiCorp Vault with a single Kubernetes ServiceAccount

Using Vault as KMS you need to configure Kubernetes authentication method as described in official documentation.

If token reviewer is used, you will need to configure service account for that also like in example to be able to review jwt tokens.

Configure a role(s) for service accounts used for ceph-csi:

  • provisioner service account (rbd-csi-provisioner) requires only delete permissions to delete passphrases on PVC delete
  • nodeplugin service account (rbd-csi-nodeplugin) requires create and read permissions to save new keys and retrieve existing

Configuring Hashicorp Vault with a ServiceAccount per Tenant

For deployments where a single ServiceAccount for accessing Hashicorp Vault is not suitable, it is possible to configure a ServiceAccount per Tenant to access the KMS. In order to configure this, each Tenant will need to have its own ServiceAccount in the Kubernetes Namespace where the volumes are created. The ServiceAccount is expected to be called ceph-csi-vault-sa by default. This can be changed by setting the tenantSAName option to a different value. An example of the global configuration that can be done in the Kubernetes Namespace where Ceph-CSI is deployed can be found in kms-config.yaml where the encryptionKMSType is set to vaulttenantsa.

Most notably, the Vault Tokens KMS configuration can be used, without the Token configuration, but with added tenantSAName and vaultRole options.

Tenants do have the ability to reconfigure parts of the connection details to the Vault service. It will often be required to set the backend path to a location where the Tenant can manage the secrets. These changes can be done by placing a ConfigMap called ceph-csi-kms-config in the Tenants Namespace, an example is available.

As each ServiceAccount needs to be added to the Vault configuration, the administrator of the service will need to apply the permissions by creating a Vault Policy that allows a ServiceAccount to access a key-value store in the KMS. In the Ceph-CSI automated testing, there is a Kubernetes Job that sets this up for a single Tenant that uses the Kubernetes Namespace tenant.

Configuring Amazon KMS

Amazon KMS can be used to encrypt and decrypt the passphrases that are used for encrypted RBD images. When a volume is created, a passphrase will be generated, which will be encrypted by the KMS and stored in the volumes metadata. Upon attaching the volume to a Pod, the worker node requests the KMS to decrypt the passphrase, after which it can be used to open the device with cryptsetup and provide access to it for the Pod.

There are a few settings that need to be included in the KMS configuration file:

  1. KMS_PROVIDER: should be set to aws-metadata.
  2. KMS_SECRET_NAME: name of the Kubernetes Secret (in the Namespace where Ceph-CSI is deployed) which contains the credentials for communicating with AWS. This defaults to ceph-csi-aws-credentials.
  3. AWS_REGION: the region where the AWS KMS service is available.

The Secret with credentials for the AWS KMS is expected to contain:

  1. AWS_ACCESS_KEY_ID: ID of the key to use for encrypting/decrypting
  2. AWS_SECRET_ACCESS_KEY: secret for the key to use
  3. AWS_SESSION_TOKEN: (optional) session token, usually empty
  4. AWS_CMK_ARN: Custom Master Key, ARN for the key used to encrypt the passphrase

This Secret is expected to be created by the administrator who deployed Ceph-CSI.

Encryption prerequisites

In order for encryption to work you need to make sure that dm-crypt kernel module is enabled on the nodes running ceph-csi attachers.

If custom image is built for the rbd-plugin instance, make sure that it contains cryptsetup tool installed to be able to use encryption.