Select the Install Disk

A machine that boots Talos from an ISO or over PXE runs it in memory until Talos is installed to a disk. Omni installs Talos when the machine is added to a cluster, or when you select Install Talos for it on the Machines page. A machine booted from a disk image is already installed, so the install disk does not apply to it. Installing Talos is a one-time operation. On an installed machine, Omni always uses the disk Talos is installed on. A different install disk is used only after the machine is wiped and Talos is installed again. Omni selects the install disk automatically. To use a different disk, select it for the machine. The selection is stored in the MachineInstallDiskConfig resource, which has the machine ID as its ID. It belongs to the machine, not to a cluster, so it is kept when the machine is removed from a cluster.

The MachineInstallDiskConfig resource and disk selectors require Omni v1.11.0 or later.Config patches cannot set the install disk. Omni rejects patches that set machine.install.disk and patches that contain an UnattendedInstallConfig document.

You can select the disk by its path, e.g., /dev/sdb, or by a disk selector. A disk path or a disk selector can select any disk of the machine, including the disks the automatic selection skips. Make sure it does not match a member of an MD RAID array, since installing Talos to it breaks the array.

UI
Cluster templates
CLI
Terraform

On the cluster create and scale pages, assign the machine to the control plane or to a worker machine set. An Install Disk dropdown then appears next to it, unless the machine is already installed:

Auto: no selection, Omni selects the disk automatically. The disk it currently selects is shown next to it in parentheses.
A disk path, e.g., /dev/sdb: selects that disk. Disks built on top of other disks show their member disks, e.g., /dev/md0 (on sdb, sdc).
Selector: shown when the machine has a disk selector. The disk the selector currently matches is shown next to it in parentheses. Hover over it to see the expression.

The dropdown lists only the disks marked selectable in MachineInstallDiskStatus. The UI cannot create disk selectors. Use cluster templates, omnictl or Terraform for them.The Install Talos action on the Machines page has its own Install Disk dropdown. It defaults to the disk Omni selects for the machine. The disk you pick there is used only for that install, and it is not stored in MachineInstallDiskConfig.

Set install.disk or install.diskSelector in the Machine document. They are mutually exclusive.

kind: Machine
name: 27c16241-96bf-4f17-9579-ea3a6c4a3ca8
install:
  diskSelector: disk.serial == "S3EVNX0K123456"

Removing the install section deletes the MachineInstallDiskConfig created by the template, so Omni selects the disk automatically again. A MachineInstallDiskConfig created in the UI, with omnictl or with Terraform is kept.
Removing the machine from the template keeps its MachineInstallDiskConfig.

See the cluster templates reference for the other fields of the Machine document.

Create a MachineInstallDiskConfig file named install-disk.yaml, using the machine ID as the resource ID:
metadata: namespace: default type: MachineInstallDiskConfigs.omni.sidero.dev id: <machine-id> spec: diskselector: disk.serial == "S3EVNX0K123456"
To select the disk by its path, set disk: /dev/sdb instead of diskselector.
Apply it:
omnictl apply -f install-disk.yaml

To let Omni select the disk automatically again, delete the resource:

omnictl delete machineinstalldiskconfigs <machine-id>

Use the omni_machine_install_disk resource:

resource "omni_machine_install_disk" "this" {
  machine_id    = "27c16241-96bf-4f17-9579-ea3a6c4a3ca8"
  disk_selector = "disk.serial == \"S3EVNX0K123456\""
}

To select the disk by its path, set disk = "/dev/sdb" instead of disk_selector.

Automatic selection

When a machine has no MachineInstallDiskConfig, Omni selects the smallest disk that is:

larger than 5 GB
not read-only and not a CD-ROM drive
not a member of another disk, e.g., a disk in an MD RAID array
not built on top of other disks, e.g., an MD RAID array or a device-mapper volume

USB disks are selected only when no other disk qualifies. From disks of the same size, Omni selects the first one by path.

Disk selectors

A disk selector is a Common Expression Language (CEL) expression evaluated against every disk of the machine. It uses the same variables as the Talos disk selectors. A disk selector can target disks by their stable properties:

disk.serial == "S3EVNX0K123456": the disk with this serial number.
'/dev/disk/by-path/pci-0000:00:1f.2-ata-1' in disk.symlinks: the disk with this stable symlink.
'/dev/disk/by-id/md-name-talos:boot' in disk.symlinks: the MD RAID array named boot.

An expression that starts with a quote must be quoted in YAML, e.g., diskSelector: "'/dev/disk/by-id/md-name-talos:boot' in disk.symlinks". When a disk selector matches more than one disk, Omni selects the first regular disk by path. A disk built on top of other disks, such as an MD RAID array, is selected only when it is the only match. Installing Talos to an MD RAID array requires Talos v1.14 or later. Create the array with the config patches in Boot from a RAID1 array. Select it as the install disk with a disk selector instead of the UnattendedInstallConfig document shown there, which Omni does not accept.

Check the install disk of a machine

Omni stores the install disk it uses for each machine in the MachineInstallDiskStatus resource:

omnictl get machineinstalldiskstatuses <machine-id> -o yaml

spec:
  disk: /dev/nvme0n1
  message: selected by the install disk selector
  disks:
    - devpath: /dev/nvme0n1
      selectable: true
      skipreason: ""
      members: []
    - devpath: /dev/md0
      selectable: true
      skipreason: built on top of other disks
      members:
        - sdb
        - sdc
    - devpath: /dev/sdb
      selectable: false
      skipreason: a member of /dev/md0
      members: []

disk: the install disk. It is empty when no disk can be used.
message: why disk is empty, or how the disk was selected.
disks: every disk of the machine. selectable says whether the UI offers the disk, and skipreason says why the automatic selection skips it.

When disk is empty, Omni does not generate the configuration of the machine, so the machine waits in its cluster. Check the message field to see why, e.g., no disk matches the install disk selector. The resource carries the cluster label of the machine, so you can list the install disks of a cluster. Replace <cluster-name> with the name of the cluster:

omnictl get machineinstalldiskstatuses -l omni.sidero.dev/cluster=<cluster-name>

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Select the Install Disk