All error codes

system_disk_not_found

HTTP 409 No system disk on this server

What happened

You asked to resize the system disk, but this server has no bootable system disk right now. That normally means it is booted from an image and its boot order points at the drive rather than at the disk.

What to do

Eject the image with DELETE /v1/servers/{id}/iso, let the server return to booting from its disk, then repeat the same request with the same idempotency key.

Retrying

Change the state this refers to, then repeat the same request with the same idempotency key.

How it arrives

{
    "type": "https://docs.fiberax.com/errors/system_disk_not_found",
    "title": "No system disk on this server",
    "status": 409,
    "code": "system_disk_not_found",
    "request_id": "a277dcd1ca652c65"
}

Branch your code on code, never on the wording of title.