rancher-flatcar-cloudinit

This is a simple tool intended to be run via guestinfo when installing Flatcar Linux in vSphere using Rancher. It serves as a workaround for a problem at the intersection of Flatcar's cloud-init implementation and Rancher v2.6.

Problem statement

Rancher v2.6 uses the NoCloud option for bootstrapping nodes under the vSphere driver. Because vSphere has no concept similar to a "metadata url" like most cloud providers, the only other options are guestinfo, which is exposed via VMWare Tools, and ISOs mounted via virtual CDROM drives.

However, the coreos-cloudinit service built-in to Flatcar is a stripped down, no-longer-maintained tool. Flatcar and other distros of CoreOS lineage much prefer Ignition Config over cloud-config.

coreos-cloudinit does not detect and mount/read the user-data and meta-data files provided on the ISO because the device is not labeled correctly and the files are not at the expected path. Even if it did try to use these files, not all of the options in the cloud-config are supported by flatcar's minimal coreos-cloudinit.

As a workaround, rancher-flatcar-cloudinit was purpose-built to be run by coreos-cloudinit, which still supports executing scripts passed in via guestinfo.coreos.config.data. rancher-flatcar-cloudinit supports the very minimal number of options in Rancher's cloud-config, enough to allow Rancher to continue bootstrapping the node.

Related issues

Usage

guestinfo

Add a snippet like this to guestinfo.coreos.config.data:

#!/bin/bash
wget --timeout 300 -q https://github.com/PennState/rancher-flatcar-cloudinit/releases/download/v0.2.1/rancher-flatcar-cloudinit_0.2.1_linux_amd64 -O /tmp/rancher-flatcar-cloudinit
chmod 755 /tmp/rancher-flatcar-cloudinit
/tmp/rancher-flatcar-cloudinit

OVA settings

If you are using the official Flatcar Linux OVA file, you must disable vApp Options after converting the VM to a Template. The coreos-cloudinit tool seems to prefer the OVF Environment data over data contained in guestinfo.

ssh user

You will also need to edit the nodeTemplate in the API. Set vmwarevsphereConfig.sshUser=rancher. The default docker user already exists and cannot be modified.