Boot customization

About boot customization

The boot behaviour of a image can be customized. To do so when creating an image you may specify optional kernel parameters that will be respected at boot time.

Using kernel parameters

In this example we’ll demonstrate how to specify kernel parameters for boot customization.

UI

Prerequisites:

• Successfully authenticated in the UI of a STEC instance.

Steps:

1. Follow the generic image creation steps as described in the getting started guide.

2. In the step that allows you to specify kernel parameters, specify one or more supported parameter. The generic syntax is key=value and every kv-pair is separated by using space as a delimiter. Click ‘next’ when done.

   

3. Follow the remaining image creation steps. The resulting review should indicate that your two options are included in the image. They’ll be part of any installation medium generated from this image. Click the “create” button to create the image.

   

4. The rest of the process is identical to the one outlined in the regular image creation procedure.

CLI

Prerequisites:

• Successfully authenticated with a STEC instance.
• Kubeconfig for the STEC instance is exported in your terminal session.
• Tools: a generic Linux bash terminal, kubectl.

Steps:

1. Follow the generic image creation steps as described in the getting started guide.

2. When creating the manifest file for your new EdgeImage make sure to populate the extraKernelArgs using one or more supported kernel parameters.

   > cat <<EOF | kubectl apply -f -
   apiVersion: edge.stackit.cloud/v1alpha1
   kind: EdgeImage
   metadata:
   name: bootfoo
   namespace: default
   spec:
   schematic: |
       customization:
   extraKernelArgs:
   - talos.hostname=custom
   - talos.dashboard.disabled=0
   systemExtensions:
   officialExtensions: []
   overlay: {}   talosVersion: v1.10.5-stackit.v0.21.0
   EOF
   
   edgeimage.edge.stackit.cloud/bootfoo created
   
   > kubectl get EdgeImage/bootfoo
   
   NAME AGE
   bootfoo  109s

3. The rest of the process is identical to the one outlined in the regular image creation procedure.

You can optionally review or change the kernel parameters of a STEC boot medium by pressing the ‘e’ key during bootloader selection.

Common parameters

This section guides you through the most common boot parameters by example.

When you configure a setting in the kernel parameters it will only take affect when there is no machine configuration applied yet. This means that once your host becomes part of a cluster (exits maintenance stage), those configurations will be overwritten by the machine configuration. Please be aware that when you reset a host the initial kernel parameters of the image will be in effect again, even if you had different settings in effect when the machine configuration was still applied. If that’s not what you want you’ll have to edit the machine configuration of a host to overwrite the kernel parameters using the machine.install.extraKernelArgs.

Static network

You may have to configure a static IP address so that the STEC node is able to reach your STEC instance. This is done through using the ip kernel parameter.

General syntax

# kernel args
ip=<CLIENT_IP>:<SERVER_IP>:<GATEWAY_IP>:<NETMASK>:<HOSTNAME>:<DEVICE>:<AUTOCONF>:<DNS_SERVER_IP_0>:<DNS_SERVER_IP_1>:<NTP_SERVER_IP>

Predictable Interface Names are used for all NICs by default. If you want to use legacy naming you may add net.ifnames=0 to the kernel command line as well or use a dummy device selector as indicated in the article. Cloud Platforms still use the legacy naming scheme as Talos automatically adds net.ifnames=0 to the kernel command for those.

• Predictable Interface Names
• Network Device Selector

Example usage

Syntax example

# kernel args
ip=172.16.0.11::172.16.0.1:255.255.255.0:foo:eth0:none:1.1.1.1:1.0.0.1:time.cloudflare.com

UI example

1. From the UI when creating an image you’ll be presented with a input field for the kernel parameters to integrate into the image.

   

2. Add the kernel parameters as needed. If you have to add multiple parameters use space as a delimiter.

   

3. When reviewing the image parameters you should find all kernel parameters that will be part of the image listed.

   

Internet proxy

STACKIT Edge Cloud requires a outbound, HTTPS connection in order for the STEC node to register with your STEC instance hosted on stackit.cloud. You may have to configure a internet proxy if there is no direct internet connection from the STEC node you’re trying to install. This is done through using the talos.environment kernel parameter.

Talos Linux requires internet access to download the Talos installer and container images, as described in the Talos documentation. However: if you have a internal registry mirror you may configure this mirror to be used instead. This can be configured either post-boot using the machine configuration or pre-boot using the talos.config Kernel parameter.

General syntax

# kernel args
talos.environment=KEY=VALUE

Example usage

Syntax example

# kernel args
talos.environment=http_proxy=http://proxy.example.net:8080 talos.environment=https_proxy=http://proxy.example.net:8443 talos.environment=no_proxy=localhost,127.0.0.1,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,.cluster.local.,.cluster.local,.svc,.svc.

UI example

1. From the UI when creating an image you’ll be presented with a input field for the kernel parameters to integrate into the image.

   

2. Add the kernel parameters as needed. If you have to add multiple parameters use space as a delimiter.

   

3. When reviewing the image parameters you should find all kernel parameters that will be part of the image listed.

   

References

• Talos documentation on kernel parameters