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Several configuration documents share common elements for configuring volumes in Talos Linux:

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Disk Selector

The diskSelector field is utilized to choose the disk where the volume will be provisioned. It is a Common Expression Language (CEL) expression that evaluates against the available disks. The volume will be provisioned on the first disk that matches the expression and has sufficient free space for the volume. The expression is evaluated in the following context:
  • system_disk (bool) - indicates if the disk is the system disk
  • disk (Disks.block.talos.dev) - the disk resource being evaluated
Note: The system_disk variable is only populated after Talos installation, so you might see an error about system_disk not being defined before installation finishes.
For the disk resource, any field available in the resource specification can be used (use talosctl get disks -o yaml to see the output for your machine): 
dev_path: /dev/nvme0n1
size: 10485760000
pretty_size: 10 GB
io_size: 512
sector_size: 512
readonly: false
cdrom: false
model: QEMU NVMe Ctrl
serial: deadbeef
wwid: nvme.1b36-6465616462656566-51454d55204e564d65204374726c-00000001
bus_path: /pci0000:00/0000:00:09.0/nvme
sub_system: /sys/class/block
transport: nvme
symlinks:
    - /dev/disk/by-diskseq/11
    - /dev/disk/by-id/ata-QEMU_HARDDISK_QM00001
    - /dev/disk/by-path/pci-0000:00:1f.2-ata-1
    - /dev/disk/by-path/pci-0000:00:1f.2-ata-1.0
Additionally, constants for disk size multipliers are available:
  • KiB, MiB, GiB, TiB, PiB, EiB - binary size multipliers (1024)
  • kB, MB, GB, TB, PB, EB - decimal size multipliers (1000)
The disk expression is evaluated against each available disk, and the expression should either return true or false. If the expression returns true, the disk is selected for provisioning.
Note: In CEL, signed and unsigned integers are not interchangeable. Disk sizes are represented as unsigned integers, so suffix u should be used in constants to avoid type mismatch, e.g. disk.size > 10u * GiB.
Examples of disk selector expressions:
  • disk.transport == 'nvme': select the NVMe disks only
  • disk.transport == 'scsi' && disk.size < 2u * TiB: select SCSI disks smaller than 2 TiB
  • disk.serial.startsWith('deadbeef') && !cdrom: select disks with serial number starting with deadbeef and not of CD-ROM type
  • '/dev/disk/by-path/pci-0000:00:1f.2-ata-1' in disk.symlinks: select disks with a specific stable symlink

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Minimum, Maximum and Grow

The minSize and maxSize fields define the minimum and maximum size of the volume, respectively. Talos Linux will always ensure that the volume is at least minSize in size and will not exceed maxSize. If maxSize is not set, the volume will grow to utilize the maximum available space on the disk. The grow flag controls what happens when the volume already exists:
  • On initial creation: grow is ignored. The new volume is created between minSize and maxSize (or full disk if maxSize is unset).
  • On subsequent boots (when the volume already exists):
    • If grow: false, the existing volume size is never changed.
    • If grow: true, and the current volume is smaller than maxSize (or maxSize is unset), Talos will expand the volume to fill available space after it.
Setting minSize might influence disk selection - if the disk does not have enough free space to satisfy the minimum size requirement, it will not be selected for provisioning.

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Volume Selector

The volumeSelector field is a CEL expression that allows you to match existing volumes based on their properties. It is evaluated against the available volumes, and the first volume that matches the expression will be picked up. The expression is evaluated in the following context:
  • volume (DiscoveredVolumes.block.talos.dev) - the volume resource being evaluated
  • disk (Disks.block.talos.dev) - the disk resource where the volume is located
For the disk field, see Disk Selector above. For the volume field, any field available in the resource specification can be used (use talosctl get discoveredvolumes -o yaml to see the output for your machine): 
metadata:
    namespace: runtime
    type: DiscoveredVolumes.block.talos.dev
    id: vda4
    version: 1
    owner: block.DiscoveryController
    phase: running
    created: 2025-07-21T13:10:56Z
    updated: 2025-07-21T13:10:56Z
spec:
    dev_path: /dev/vda4
    type: partition
    device_path: /sys/devices/pci0000:00/0000:00:07.0/virtio4/block/vda/vda4
    parent: vda
    parent_dev_path: /dev/vda
    size: 5179965440
    pretty_size: 5.2 GB
    sector_size: 512
    io_size: 512
    name: xfs
    uuid: 2f115241-781f-4817-a373-fc957d63326f
    label: EPHEMERAL
    block_size: 512
    filesystem_block_size: 4096
    probed_size: 5112856576
    partition_uuid: 73111630-87ed-4aad-bffb-af6d0f55ab3c
    partition_type: 0fc63daf-8483-4772-8e79-3d69d8477de4
    partition_label: EPHEMERAL
    partition_index: 4
The size multipliers constants are also available for the volume selector expression. Examples of volume selector expressions:
  • volume.partition_label == 'MY-DATA': match volumes with partition label MY-DATA
  • volume.name == 'xfs' && volume.size > 1000u * TB: match XFS volumes larger than 1000 TB
  • volume.name == 'xfs' && disk.transport == 'nvme': match XFS volumes on NVMe disks
  • volume.partition_index == 2 && disk.serial == 'SERIAL123': match second partition on a disk with serial number SERIAL123