Document container prepare workflow

This docs change will result in switching over to the workflow driven
container prepare by doing the following:

- Only document calling "openstack tripleo container image prepare"
  when testing more complex ContainerImagePrepare parameters
- Remove reference to containers-default-parameters.yaml, replacing it
  in overcloud deploy with containers-prepare-parameter.yaml directly
- For minor updates, instruct users to check the contents of
  containers-prepare-parameter.yaml so they know what will happen during
  the minor update

This change does not cover major upgrades to Rocky since the major
upgrade docs are still on Queens.

The rocky major upgrade instructions should describe running
"openstack tripleo container image prepare default" then merging the result
with any customized containers-default-parameters.yaml which they had
in their previous deployment (in the common case, no merging will be
needed).

Change-Id: I3eca2beeeacb31994cb870e8d4c5f3ba01051078
Blueprint: container-prepare-workflow

doc/source/install/advanced_deployment/container_image_prepare.rst

@@ -1,6 +1,6 @@
 .. _prepare-environment-containers:
 
-Container Image Preperation
+Container Image Preparation
 ===========================
 
 This documentation explains how to instruct container image preparation to do
@@ -11,7 +11,7 @@ Choosing an image registry strategy
 
 Container images need to be pulled from an image registry which is reliably
 available to overcloud nodes. The three common options to serve images are to
-use the default registry, the registry availably on the undercloud, or an
+use the default registry, the registry available on the undercloud, or an
 independently managed registry. During deployment the environment parameter
 `ContainerImagePrepare` is used to specify any desired behaviour, including:
 
@@ -112,13 +112,16 @@ refer to the images in `push_destination` instead of `namespace`.
 
 Running container image prepare
 ...............................
-The prepare operations are actually run at the following times:
+The prepare operations are run at the following times:
 
 #. During ``undercloud install`` when `undercloud.conf` has
    `container_images_file=$HOME/containers-prepare-parameter.yaml` (see
    :ref:`install_undercloud`)
-#. Before overcloud deploy when ``openstack tripleo container image prepare``
-   is run (see :ref:`overcloud-prepare-container-images`)
+#. During ``overcloud deploy`` when a `ContainerImagePrepare` parameter is
+   provided by including the argument `-e
+   $HOME/containers-prepare-parameter.yaml`
+   (see :ref:`overcloud-prepare-container-images`)
+#. Any other time when ``openstack tripleo container image prepare`` is run
 
 
 Options available in heat parameter ContainerImagePrepare

doc/source/install/containers_deployment/overcloud.rst

@@ -49,24 +49,10 @@ with images required by the overcloud deploy by generating the following
 
 See :ref:`prepare-environment-containers` for details on using
 `containers-prepare-parameter.yaml` to control what can be done
-during container image preparation.
+with image preparation during overcloud deployment.
 
 .. _overcloud-prepare-container-images:
 
-Running container image prepare
-...............................
-
-The ``openstack tripleo container image prepare`` command performs all of the
-required prepare tasks as specified by `~/containers-prepare-parameter.yaml`.
-This generates the environment file `~/containers-default-parameters.yaml`
-which contains all of the container image parameters needed for the overcloud
-deploy. The prepare is run with the command::
-
-  openstack tripleo container image prepare \
-    -e ~/containers-prepare-parameter.yaml
-    --roles-file /usr/share/openstack-tripleo-heat-templates/roles_data.yaml \
-    --output-env-file ~/containers-default-parameters.yaml
-
 Deploying the containerized Overcloud
 -------------------------------------
 
@@ -75,7 +61,7 @@ baremetal :ref:`deploy-the-overcloud` documentation with the exception that it
 requires an extra environment file to be added to the ``openstack overcloud
 deploy`` command::
 
-  -e ~/containers-default-parameters.yaml
+  -e ~/containers-prepare-parameter.yaml
 
 If deploying with highly available controller nodes, include the
 following extra environment file in addition to the above and in place

doc/source/install/post_deployment/package_update.rst

@@ -166,9 +166,10 @@ then execute these. See bug 1715557_ for more information about this mechanism
 and its implementation.
 
 
-1. You must first re-run the `openstack overcloud container image prepare`
-command to generate a docker registry file with the latest images see
-:doc:`../containers_deployment/overcloud` for more information.
+1. Confirm that your `$HOME/containers-prepare-parameter.yaml`
+`ContainerImagePrepare` parameter includes a `tag_from_label` value, so that
+the latest images are discovered on update, otherwise edit the `tag` value
+to specify what image versions to update to.
 
 
 2. Perform a heat stack update to generate the ansible playbooks, specifying