SOP Create RHCOS ignition files

Signed-off-by: David Kirwan <dkirwan@redhat.com>

modules/ocp4/pages/sop_create_machineconfigs.adoc

@@ -0,0 +1,38 @@
+== Create MachineConfigs to Configure RHCOS
+
+=== Resources
+
+- [1] https://coreos.github.io/butane/getting-started/[Butane Getting Started]
+- [2] https://docs.openshift.com/container-platform/4.8/post_installation_configuration/machine-configuration-tasks.html#installation-special-config-chrony_post-install-machine-configuration-tasks[OCP4 Post Installation Configuration]
+
+=== Butane
+"Butane (formerly the Fedora CoreOS Config Transpiler) is a tool that consumes a Butane Config and produces an Ignition Config, which is a JSON document that can be given to a Fedora CoreOS machine when it first boots." [1]
+
+Butane is available in a container image, we can pull the latest version locally like so:
+
+----
+# Pull the latest release
+podman pull quay.io/coreos/butane:release
+
+# Run butane using standard in and standard out
+podman run -i --rm quay.io/coreos/butane:release --pretty --strict < your_config.bu > transpiled_config.ign
+
+# Run butane using files.
+podman run --rm -v /path/to/your_config.bu:/config.bu:z quay.io/coreos/butane:release --pretty --strict /config.bu > transpiled_config.ign
+----
+
+We can create a CLI alias to make running the Butane container much easier like so:
+
+----
+alias butane='podman run --rm --tty --interactive \
+              --security-opt label=disable        \
+              --volume ${PWD}:/pwd --workdir /pwd \
+              quay.io/coreos/butane:release'
+----
+
+For more detailed information on how to structure your Butane file see [1]. Once created you can convert the butane config to an igntion file like so:
+
+----
+butane master_chrony_machineconfig.bu -o master_chrony_machineconfig.yaml
+butane worker_chrony_machineconfig.bu -o worker_chrony_machineconfig.yaml
+----

modules/ocp4/pages/sops.adoc

@@ -2,3 +2,4 @@
 
 - xref:sop_installation.adoc[SOP Openshift 4 Installation on Fedora Infra]
 - xref:sop_configure_baremetal_pxe_uefi_boot.adoc[SOP Configure Baremetal PXE-UEFI Boot]
+- xref:sop_create_machineconfigs.adoc[SOP Create MachineConfigs to Configure RHCOS]