The title is self explanatory. https://rancher.com/docs/os/v1.0/en/ is down. 404 not found on all pages
Sorry. It appears that was an archived link to previous versions. Here is the latest versions always.
https://rancher.com/docs/os/v1.x/en/installation/configuration/
It seems core conceptual documents that linked off the initial documenation are down.
https://rancher.com/docs/os/installation/configuration/#cloud-config