Remove support for CoreOS Container Linux (#6576)

docs/_sidebar.md

@@ -27,7 +27,7 @@
   * [vSphere](/docs/vsphere.md)
 * Operating Systems
   * [Debian](docs/debian.md)
-  * [Coreos](docs/coreos.md)
+  * [Flatcar Container Linux](docs/flatcar.md)
   * [Fedora CoreOS](docs/fcos.md)
   * [OpenSUSE](docs/opensuse.md)
 * Advanced

docs/flatcar.md

@@ -0,0 +1,14 @@
+Flatcar Container Linux bootstrap
+===============
+
+Example with Ansible:
+
+Before running the cluster playbook you must satisfy the following requirements:
+
+General Flatcar Pre-Installation Notes:
+
+- Ensure that the bin_dir is set to `/opt/bin`
+- ansible_python_interpreter should be `/opt/bin/python`. This will be laid down by the bootstrap task.
+- The default resolvconf_mode setting of `docker_dns` **does not** work for Flatcar. This is because we do not edit the systemd service file for docker on Flatcar nodes. Instead, just use the `host_resolvconf` mode. It should work out of the box.
+
+Then you can proceed to [cluster deployment](#run-deployment)

docs/vagrant.md

@@ -17,7 +17,7 @@ By default, Vagrant uses Ubuntu 18.04 box to provision a local cluster. You may
 Customize `$os` variable in `Vagrantfile` or as override, e.g.,:
 
 ```ShellSession
-echo '$os = "coreos-stable"' >> vagrant/config.rb
+echo '$os = "flatcar-stable"' >> vagrant/config.rb
 ```
 
 The supported operating systems for vagrant are defined in the `SUPPORTED_OS` constant in the `Vagrantfile`.