User Volumes allow to treat available disk space as a pool of allocatable resource, which can be dynamically allocated to different applications. The user volumes are supposed to be used mostly for hostPath mounts in Kubernetes, but they can be used for other purposes as well. When a user volume configuration is applied, Talos Linux will either locate an existing volume or provision a new one. The volume will be created on the disk which satisfies the diskSelector expression and has enough free space to satisfy the minSize requirement. The user volume is identified by a unique name, which is used both as a mount location and as a label for the volume. The volume name must be unique across all user volumes, and it should be between 1 and 34 characters long, and can only contain ASCII letters, digits, and - (dash) characters. The volume label is derived from the volume name as u-<volume-name>, and it is used to identify the volume on the disk after initial provisioning. The volume mount location is /var/mnt/<volume-name>, and it gets automatically propagated into the kubelet container to provide additional features like subPath mounts. Disk encryption can be optionally enabled for user volumes.

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Creating User Volumes

To create a user volume, append the following document to the machine configuration: 
# user-volume.patch.yaml
apiVersion: v1alpha1
kind: UserVolumeConfig
name: local-volume
provisioning:
  diskSelector:
    match: disk.transport == 'nvme'
  minSize: 100GB
  maxSize: 200GB
For example, this machine configuration patch can be applied using the following command: 
talosctl --nodes <NODE> patch mc --patch @user-volume.patch.yaml
In this example, a user volume named local-volume is created on the first NVMe disk which has 100GB of disk space available, and it will be created as maximum of 200GB if that space is available. The status of the volume can be checked using the following command: 
$ talosctl get volumestatus u-local-volume # note u- prefix
NAMESPACE   TYPE           ID            VERSION   TYPE        PHASE   LOCATION         SIZE
runtime     VolumeStatus   u-local-volume   2         partition   ready   /dev/nvme0n1p2   200 GB
If the volume fails to be provisioned, use the -o yaml flag to get additional details. The volume is immediately mounted to /var/mnt/local-volume: 
$ talosctl get mountstatus
NAMESPACE   TYPE          ID           VERSION   SOURCE           TARGET               FILESYSTEM   VOLUME
runtime     MountStatus   u-local-volume  2         /dev/nvme0n1p2   /var/mnt/local-volume   xfs          u-local-volume
It can be used in a Kubernetes pod as a hostPath mount: 
kind: Pod
spec:
  containers:
    - name: ceph
      volumeMounts:
        - mountPath: /var/lib/ceph
          name: local-volume
  volumes:
    - name: local-volume
      hostPath:
        path: /var/mnt/local-volume
Please note, the path inside the container can be different from the path on the host.

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Removing User Volumes

Before removing a user volume, ensure that it is not mounted in any Kubernetes pod. In order to remove a user volume, first remove the configuration document from the machine configuration. The VolumeStatus and MountStatus resources will be removed automatically by Talos Linux.
Note: The actual disk data hasn’t been removed yet, so you can re-apply the user volume configuration back and it will be re-provisioned on the same disk.
To wipe the disk data, and make it allocatable again, use the following command: 
talosctl wipe disk nvme0n1p2 --drop-partition
The nvme0n1p2 is the partition name, and it can be obtained from the VolumeStatus resource before the user volume is removed, or from the DiscoveredVolume resource any time later.
Note: If the wipe disk command fails with blockdevice is in use by volume, it means the user volume has not been removed from the machine configuration.