Update notes for upgrade procedure in Azure (#3722)

* Update notes for upgrade procedure in Azure

docker-for-azure/upgrade.md

@@ -4,27 +4,45 @@ keywords: azure, microsoft, iaas, tutorial
 title: Docker for Azure Upgrades
 ---
 
-Docker for Azure supports upgrading from one version to the next. To upgrade, apply a new version of the Azure ARM template that powers Docker for Azure. An upgrade of Docker for Azure involves:
+Docker for Azure supports upgrading from one version to the next within a specific channel. Upgrading across channels (for example, from `edge` to `stable` or `test` to `edge`) is not supported. To upgrade to a specific version, run the upgrade container corresponding to the target version for the upgrade. An upgrade of Docker for Azure involves:
 
- * Upgrading the VHD backing the manager and worker nodes (the Docker engine ships in the VHD)
+ * Upgrading the VHD backing the manager and worker nodes (Docker ships in the VHD)
  * Upgrading service containers in the manager and worker nodes
  * Changing any other resources in the Azure Resource Group that hosts Docker for Azure
 
 ## Prerequisites
 
- * We recommend only attempting upgrades of swarms with at least 3 managers. A 1-manager swarm may not be able to maintain quorum during the upgrade
- * You can only upgrade one version at a time. Skipping a version during an upgrade is not supported. Downgrades are not tested.
- * Ensure there are no nodes in the swarm in "down" status. If there are such nodes in the swarm, please remove them from the swarm using `docker node rm node-id`
+ * We recommend only attempting upgrades of swarms with at least 3 managers. A 1-manager swarm may not be able to maintain quorum during an upgrade.
+ * You can only upgrade one version at a time. Skipping a version during an upgrade is not supported.
+ * Downgrades are not tested.
+ * Upgrading across channels (`stable`, `edge`, or `testing`) is not supported.
+ * If the swarm contains nodes in the `down` state, remove them from the swarm before attempting the upgrade, using `docker node rm <node-id>`.
 
 ## Upgrading
 
 New releases are announced on the [Release Notes](release-notes.md) page.
 
-To initiate an upgrade, SSH into a manager node and issue the following command:
+To initiate an upgrade, connect a manager node using SSH and run the container corresponding to the version you want to upgrade to:
 
-    upgrade.sh https://download.docker.com/azure/stable/Docker.tmpl
+```bash
+$ docker run \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  -v /usr/bin/docker:/usr/bin/docker \
+  -ti \
+  docker4x/upgrade-azure:version-tag
+```
 
-This will initiate a rolling upgrade of the Docker swarm and service state will be maintained during and after the upgrade. Appropriately scaled services should not experience downtime during an upgrade. Note that single containers started (for example) with `docker run -d` are **not** preserved during an upgrade. This is because they are not Docker Swarm services but are known only to the individual Docker engines.
+For example, this command upgrades from 17.03 CE stable release to 17.06.0 CE stable:
+
+```bash
+$ docker run \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  -v /usr/bin/docker:/usr/bin/docker \
+  -ti \
+  docker4x/upgrade-azure:17.06.0-ce-azure1
+```
+
+This initiates a rolling upgrade of the Docker swarm. Service state is maintained during and after the upgrade. Appropriately scaled services should not experience downtime during an upgrade. Single containers which are not part of services (for example, containers started with `docker run`) are **not** preserved during an upgrade. This is because they are not Docker  services but are known only to the individual Docker engine where they are running.
 
 ## Monitoring