Modify Kernel Arguments

Add or update additional Talos kernel arguments through Omni.

You can add kernel arguments when creating installation media, or modify them later on existing machines. For a full list of available kernel arguments, refer to the Kernel argument reference documentation.

Some kernel arguments are added automatically by Omni (for example, the SideroLink arguments), while others are provided by Talos.

These automatically added arguments are not user-editable and modifying them is not supported.

This document describes how to modify additional kernel arguments only.

Add kernel arguments during installation media creation

You can include additional kernel arguments into your Talos Omni image using either cluster templates, the Omni CLI or the Omni UI.

Cluster templates

You can add kernel arguments to your machines by defining them in the machine configuration within your cluster template.

Use the kernelArgs field in your cluster template to specify which extensions to install. For more details, see the Cluster Templates reference documentation.

The code block below defines the configuration for a cluster named my-cluster, including kernel arguments for both control plane and worker machines.

kind: Cluster
name: my-cluster
kubernetes:
  version: v1.35.0
talos:
  version: v1.12.2
---
kind: ControlPlane
machines:
  - ec2d0bff-ea56-3ee5-cae3-d56663de6272
---
kind: Workers
machines:
  - ec2fe180-8445-eea2-410f-af334b831fcb
---
kind: Machine
name: ec2d0bff-ea56-3ee5-cae3-d56663de6272
install:
  disk: /dev/xvda
kernelArgs:
  - talos.dashboard.disabled=1
---
kind: Machine
name: ec2fe180-8445-eea2-410f-af334b831fcb
install:
  disk: /dev/xvda
kernelArgs:
  - console=ttyS0,115200n8

After defining your cluster template, validate it using:

omnictl cluster template validate -f cluster.yaml

If the validation succeeds, sync the template to apply the configuration to your Omni instance:

omnictl cluster template sync -f cluster.yaml --verbose

After syncing, the control plane machine will boot with the talos.dashboard.disabled=1 kernel argument, while the worker machine will boot with the console=ttyS0,115200n8 kernel argument.

CLI

You can bake kernel arguments into your image in the cli by adding the --extra-kernel-args flag when you download the Talos Omni image.

Run this command to learn more about how to bake these kernel arguments:

omnictl download --help

For example, to download a Talos Omni ISO image with the kernel argument talos.dashboard.disabled=1, run:

omnictl download iso --arch amd64 --extra-kernel-args talos.dashboard.disabled=1

You can then boot your machines with this downloaded Talos Omni image.

UI

To add kernel arguments to your machines:

1. Log in to your Omni dashboard.

2. Click the Download Installation Media button to open the Create New Media wizard.

3. On each page of the Create New Media wizard, select the appropriate options for your setup, then click Next to continue.

   The Create New Media wizard is identical to the Image Factory and it is split across multiple pages. Each page presents a different set of configuration options, such as architecture, hardware type, and Talos Linux version, that you can use to customize your Talos Omni image.

4. Select the kernel arguments you would like to boot your machines with in the Extra kernel command line arguments section, click Next and continue with your setup.

5. Select the appropriate boot option for your machine on the Schematic Ready page to download the Talos Omni image.

6. Boot your machines using the downloaded image. The selected kernel arguments will already be installed.

Once you boot your machine with kernel arguments, Omni automatically creates a KernelArgs resource for that machine. You can view and update this resource later to modify the kernel arguments.

To retrieve the resource, run:

omnictl get kernelargs $MACHINE_ID -o yaml

Example output:

metadata:
  namespace: default
  type: KernelArgs.omni.sidero.dev
  id: $MACHINE_ID
  version: 1
  owner:
  phase: running
  created: 2025-10-29T12:58:17Z
  updated: 2025-10-29T12:58:17Z
spec:
  args:
    - talos.dashboard.disabled=1
    - talos.environment=http_proxy=http://proxy.example.com:8080

Update kernel arguments on existing machines

Modifying kernel arguments on existing machines triggers an upgrade and reboots the machine.

Some conditions must be met for kernel argument updates to take effect. If these conditions are not met, they appear in the unmetconditions field of the KernelArgsStatus resource and in the UI.

UI

1. Go to the Machines tab.

2. Click the three dots next to the machine you want to modify and select Update kernel args.

3. In the popup, click the pencil icon to edit the current kernel arguments.

4. Click Update.

CLI

1. Save the existing arguments to a file:

   omnictl get kernelargs $MACHINE_ID -o yaml > kernel-args.yaml
   

Alternatively, you can create a new file manually.

2. Modify the file as needed. For example, to set talos.environment=foo=bar, update the spec.args section:

   metadata:
     namespace: default
     type: KernelArgs.omni.sidero.dev
     id: $MACHINE_ID
   spec:
     args:
       - talos.environment=foo=bar
   

3. Apply the file using omnictl:

   omnictl apply -f kernel-args.yaml
   

4. Monitor the update status:

   omnictl get kernelargsstatus $MACHINE_ID -o yaml --watch
   

   Example output:

   event: updated
   metadata:
     namespace: default
     type: KernelArgsStatuses.omni.sidero.dev
     id: $MACHINE_ID
     version: 5
     owner: KernelArgsStatusController
     phase: running
     created: 2025-10-29T12:58:17Z
     updated: 2025-10-29T13:28:32Z
   spec:
     args:
       - talos.environment=foo=bar
     currentargs:
       - console=tty0
       - console=ttyS0
     unmetconditions: []
     currentcmdline: talos.platform=metal console=tty0 console=ttyS0 init_on_alloc=1 slab_nomerge pti=on consoleblank=0 nvme_core.io_timeout=4294967295 printk.devkmsg=on selinux=1 siderolink.api=grpc://omni.example.org:8090?jointoken=w7uVuW3zbVKIYQ....VfCfSCD talos.events.sink=[fdae:41e4:649b:9303::1]:8090 talos.logging.kernel=tcp://[fdae:41e4:649b:9303::1]:8092