Add an upgrade guide

doc/source/index.rst

@@ -25,6 +25,7 @@ Documentation
    usage
    configuration
    deployment
+   upgrading
 
 Developer Documentation
 -----------------------

doc/source/upgrading.rst

@@ -0,0 +1,141 @@
+.. _upgrading:
+
+=========
+Upgrading
+=========
+
+This section describes how to upgrade from one OpenStack release to another.
+
+Preparation
+===========
+
+Before you start, be sure to back up any local changes, configuration, and
+data.
+
+Upgrading Kayobe
+================
+
+If a new, suitable version of kayobe is available, it should be installed.
+If using kayobe from a git checkout, this may be done by pulling down the new
+version from Github.  Make sure that any local changes to kayobe are committed.
+For example, to pull version 1.0.0 from the ``origin`` remote::
+
+    $ git pull origin 1.0.0
+
+If local changes were made to kayobe, these should now be reapplied.
+
+The upgraded kayobe python module and dependencies should be installed::
+
+    (kayobe-venv) $ pip install -U .
+
+Migrating Kayobe Configuration
+------------------------------
+
+Kayobe configuration options may be changed between releases of kayobe. Ensure
+that all site local configuration is migrated to the target version format. If
+using the `kayobe-config <https://github.com/stackhpc/kayobe-config>`_ git
+repository to manage local configuration, this process can be managed via git.
+For example, to fetch version 1.0.0 of the configuration from the ``origin``
+remote and merge it into the current branch::
+
+    $ git fetch origin 1.0.0
+    $ git merge 1.0.0
+
+The configuration should be manually inspected after the merge to ensure that
+it is correct.  Any new configuration options may be set at this point.  In
+particular, the following options may need to be changed if not using their
+default values:
+
+* ``kolla_openstack_release``
+* ``kolla_sources``
+* ``kolla_build_blocks``
+* ``kolla_build_customizations``
+
+Once the configuration has been migrated, it is possible to view the global
+variables for all hosts::
+
+    (kayobe-venv) $ kayobe configuration dump
+
+The output of this command is a JSON object mapping hosts to their
+configuration.  The output of the command may be restricted using the
+``--host``, ``--hosts``, ``--var-name`` and ``--dump-facts`` options.
+
+Upgrading the Control Host
+==========================
+
+Before starting the upgrade we must upgrade the Ansible control host.  Tasks
+performed here include:
+
+- Install updated Ansible role dependencies from Ansible Galaxy.
+- Generate an SSH key if necessary and add it to the current user's authorised
+  keys.
+
+To upgrade the Ansible control host::
+
+    (kayobe-venv) $ kayobe control host upgrade
+
+Upgrading the Seed
+==================
+
+Currently, upgrading the seed services is not supported.
+
+Upgrading the Overcloud
+=======================
+
+The overcloud services are upgraded in two steps.  First, new container images
+should be obtained either by building them locally or pulling them from an
+image registry.  Second, the overcloud services should be replaced with new
+containers created from the new container images.
+
+Building Container Images
+-------------------------
+
+.. note::
+
+   It is possible to use prebuilt container images from an image registry such
+   as Dockerhub.  In this case, this step can be skipped.
+
+In some cases it may be necessary to build images locally either to apply local
+image customisation or to use a downstream version of kolla.  To build images
+locally::
+
+    (kayobe-venv) $ kayobe overcloud container image build
+
+It is possible to build a specific set of images by supplying one or more
+image name regular expressions::
+
+    (kayobe-venv) $ kayobe overcloud container image build ironic- nova-api
+
+In order to push images to a registry after they are built, add the ``--push``
+argument.
+
+Pulling Container Images
+------------------------
+
+.. note::
+
+   It is possible to build container images locally avoiding the need for an
+   image registry such as Dockerhub.  In this case, this step can be skipped.
+
+In most cases suitable prebuilt kolla images will be available on Dockerhub.
+The `stackhpc account <https://hub.docker.com/r/stackhpc/>`_ provides image
+repositories suitable for use with kayobe and will be used by default.  To
+pull images from the configured image registry::
+
+    (kayobe-venv) $ kayobe overcloud container image pull
+
+Upgrading Containerised Services
+--------------------------------
+
+Containerised control plane services may be upgraded by replacing existing
+containers with new containers using updated images which have been pulled from
+a registry or built locally.
+
+To upgrade the containerised control plane services::
+
+    (kayobe-venv) $ kayobe overcloud service upgrade
+
+It is possible to specify tags for Kayobe and/or kolla-ansible to restrict the
+scope of the upgrade::
+
+    (kayobe-venv) $ kayobe overcloud service upgrade --tags config --kolla-tags keystone