---
title: "Kernel"
description: "Linux kernel reference."
---

## Commandline Parameters

Talos supports a number of kernel commandline parameters.  Some are required for
it to operate.  Others are optional and useful in certain circumstances.

Several of these are enforced by the Kernel Self Protection Project [KSPP](https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings).

**Required** parameters:

* `talos.platform`: can be one of `aws`, `azure`, `container`, `digitalocean`, `equinixMetal`, `gcp`, `hcloud`, `metal`, `nocloud`, `openstack`, `oracle`, `scaleway`, `upcloud`, `vmware` or `vultr`
* `slab_nomerge`: required by KSPP
* `pti=on`: required by KSPP

**Recommended** parameters:

* `init_on_alloc=1`: advised by KSPP, enabled by default in kernel config
* `init_on_free=1`: advised by KSPP, enabled by default in kernel config

### Available Talos-specific parameters

#### `ip`

Initial configuration of the interface, routes, DNS, NTP servers (multiple `ip=` kernel parameters are accepted).

Full documentation is available in the [Linux kernel docs](https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt).

`ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:<dns0-ip>:<dns1-ip>:<ntp0-ip>`

Talos will use the configuration supplied via the kernel parameter as the initial network configuration.
This parameter is useful in the environments where DHCP doesn't provide IP addresses or when default DNS and NTP servers should be overridden
before loading machine configuration.
Partial configuration can be applied as well, e.g. `ip=:::::::<dns0-ip>:<dns1-ip>:<ntp0-ip>` sets only the DNS and NTP servers.

IPv6 addresses can be specified by enclosing them in the square brackets, e.g. `ip=[2001:db8::a]:[2001:db8::b]:[fe80::1]::controlplane1:eth1::[2001:4860:4860::6464]:[2001:4860:4860::64]:[2001:4860:4806::]`.

`<device>` can be traditional interface naming scheme `eth0, eth1` or `enx<MAC>`, example: `enx78e7d1ea46da`

DCHP can be enabled by setting `<autoconf>` to `dhcp`, example: `ip=:::::eth0.3:dhcp`.
Alternative syntax is `ip=eth0.3:dhcp`.

#### `bond`

Bond interface configuration.

Full documentation is available in the [Dracut kernel docs](https://man7.org/linux/man-pages/man7/dracut.cmdline.7.html).

`bond=<bondname>:<bondslaves>:<options>:<mtu>`

Talos will use the `bond=` kernel parameter if supplied to set the initial bond configuration.
This parameter is useful in environments where the switch ports are suspended if the machine doesn't setup a LACP bond.

If only the bond name is supplied, the bond will be created with `eth0` and `eth1` as slaves and bond mode set as `balance-rr`

All these below configurations are equivalent:

* `bond=bond0`
* `bond=bond0:`
* `bond=bond0::`
* `bond=bond0:::`
* `bond=bond0:eth0,eth1`
* `bond=bond0:eth0,eth1:balance-rr`

An example of a bond configuration with all options specified:

`bond=bond1:eth3,eth4:mode=802.3ad,xmit_hash_policy=layer2+3:1450`

This will create a bond interface named `bond1` with `eth3` and `eth4` as slaves and set the bond mode to `802.3ad`, the transmit hash policy to `layer2+3` and bond interface MTU to 1450.

#### `vlan`

The interface vlan configuration.

Full documentation is available in the [Dracut kernel docs](https://man7.org/linux/man-pages/man7/dracut.cmdline.7.html).

Talos will use the `vlan=` kernel parameter if supplied to set the initial vlan configuration.
This parameter is useful in environments where the switch ports are VLAN tagged with no native VLAN.

Only one vlan can be configured at this stage.

An example of a vlan configuration including static ip configuration:

`vlan=eth0.100:eth0 ip=172.20.0.2::172.20.0.1:255.255.255.0::eth0.100:::::`

This will create a vlan interface named `eth0.100` with `eth0` as the underlying interface and set the vlan id to 100 with static IP 172.20.0.2/24 and 172.20.0.1 as default gateway.

#### `panic`

The amount of time to wait after a panic before a reboot is issued.

Talos will always reboot if it encounters an unrecoverable error.
However, when collecting debug information, it may reboot too quickly for
humans to read the logs.
This option allows the user to delay the reboot to give time to collect debug
information from the console screen.

A value of `0` disables automatic rebooting entirely.

#### `talos.config`

The URL at which the machine configuration data may be found (only for `metal` platform, with the kernel parameter `talos.platform=metal`).

This parameter supports variable substitution inside URL query values for the following case-insensitive placeholders:

* `${uuid}` the SMBIOS UUID
* `${serial}` the SMBIOS Serial Number
* `${mac}` the MAC address of the first network interface attaining link state `up`
* `${hostname}` the hostname of the machine

The following example

`http://example.com/metadata?h=${hostname}&m=${mac}&s=${serial}&u=${uuid}`

may translate to

`http://example.com/metadata?h=myTestHostname&m=52%3A2f%3Afd%3Adf%3Afc%3Ac0&s=0OCZJ19N65&u=40dcbd19-3b10-444e-bfff-aaee44a51fda`

For backwards compatibility we insert the system UUID into the query parameter `uuid` if its value is empty. As in
`http://example.com/metadata?uuid=` => `http://example.com/metadata?uuid=40dcbd19-3b10-444e-bfff-aaee44a51fda`

##### `metal-iso`

When the kernel parameter `talos.config=metal-iso` is set, Talos will attempt to load the machine configuration from any block device with a filesystem label of `metal-iso`.
Talos will look for a file named `config.yaml` in the root of the filesystem.

For example, such ISO filesystem can be created with:

```sh
mkdir iso/
cp config.yaml iso/
mkisofs -joliet -rock -volid 'metal-iso' -output config.iso iso/
```

#### `talos.platform`

The platform name on which Talos will run.

Valid options are:

* `aws`
* `azure`
* `container`
* `digitalocean`
* `equinixMetal`
* `gcp`
* `hcloud`
* `metal`
* `nocloud`
* `openstack`
* `oracle`
* `scaleway`
* `upcloud`
* `vmware`
* `vultr`

#### `talos.board`

The board name, if Talos is being used on an ARM64 SBC.

Supported boards are:

* `bananapi_m64`: Banana Pi M64
* `libretech_all_h3_cc_h5`: Libre Computer ALL-H3-CC
* `rock64`: Pine64 Rock64
* `rpi_4`: Raspberry Pi 4, Model B

#### `talos.hostname`

The hostname to be used.
The hostname is generally specified in the machine config.
However, in some cases, the DHCP server needs to know the hostname
before the machine configuration has been acquired.

Unless specifically required, the machine configuration should be used
instead.

#### `talos.shutdown`

The type of shutdown to use when Talos is told to shutdown.

Valid options are:

* `halt`
* `poweroff`

#### `talos.network.interface.ignore`

A network interface which should be ignored and not configured by Talos.

Before a configuration is applied (early on each boot), Talos attempts to
configure each network interface by DHCP.
If there are many network interfaces on the machine which have link but no
DHCP server, this can add significant boot delays.

This option may be specified multiple times for multiple network interfaces.

#### `talos.experimental.wipe`

Resets the disk before starting up the system.

Valid options are:

* `system` resets system disk.

#### `talos.unified_cgroup_hierarchy`

Talos defaults to always using the unified cgroup hierarchy (`cgroupsv2`), but `cgroupsv1`
can be forced with `talos.unified_cgroup_hierarchy=0`.

> Note: `cgroupsv1` is deprecated and it should be used only for compatibility with workloads which don't support `cgroupsv2` yet.
