image-url-command

The --hcloud-image-url-command and --baremtal-image-url-command for the caph controller can be used to execute a custom command to install the node image.

This provides you a flexible way to create nodes.

The script/binary will be copied into the rescue system and executed.

You need to enable two things:

The caph binary must get argument. Example: --[hcloud|baremetal]-image-url-command=/shared/image-url-command.sh
for hcloud: The hcloudmachine resource must have spec.imageURL set (usually via a hcloudmachinetemplate)
for baremetal: The hetznerbaremetal resource must use useCustomImageURLCommand: true .

The command will get the imageURL, bootstrap-data, machine-name of the corresponding machine and the root devices (seperated by spaces) as argument.

Example:

bash

/root/image-url-command oci://example.com/yourimage:v1 /root/bootstrap.data my-md-bm-kh57r-5z2v8-zdfc9 'sda sdb'

It is up to the command to download from that URL and provision the disk accordingly. This command must be accessible by the controller pod. You can use an initContainer to copy the command to a shared emptyDir.

The env var OCI_REGISTRY_AUTH_TOKEN from the caph process will be set for the command, too.

The command must end with the last line containing IMAGE_URL_DONE. Otherwise the execution is considered to have failed.

The controller uses url.ParseRequestURI (Go function) to validate the imageURL.

A Kubernetes event will be created in both (success, failure) cases containing the output (stdout and stderr) of the script. If the script takes longer than 7 minutes, the controller cancels the provisioning.

We measured these durations for hcloud:

oldState	newState	avg(s)	min(s)	max(s)
	Initializing	3.30	2.00	5.00
Initializing	EnablingRescue	19.20	11.00	21.00
EnablingRescue	BootingToRescue	14.20	9.00	23.00
BootingToRescue	RunningImageCommand	38.20	37.00	42.00
RunningImageCommand	BootingToRealOS	62.40	56.00	80.00
BootingToRealOS	OperatingSystemRunning	1.80	1.00	3.00

The duration of the state RunningImageCommand depends heavily on your script.