Merge pull request #29173 from lalyos/patch-2

Note about potential plugin issue when upgrading

CHANGELOG.md

@@ -7,6 +7,22 @@ be found.
 
 ## 1.13.0 (2016-12-08)
 
+**IMPORTANT**: In Docker 1.13, the managed plugin api changed, as compared to the experimental
+version introduced in Docker 1.12. You must **uninstall** plugins which you installed with Docker 1.12
+_before_ upgrading to Docker 1.13. You can uninstall plugins using the `docker plugin rm` command.
+
+If you have already upgraded to Docker 1.13 without uninstalling
+previously-installed plugins, you may see this message when the Docker daemon
+starts:
+
+    Error starting daemon: json: cannot unmarshal string into Go value of type types.PluginEnv
+
+To manually remove all plugins and resolve this problem, take the following steps:
+
+1. Remove plugins.json from: `/var/lib/docker/plugins/`.
+2. Restart Docker. Verify that the Docker daemon starts with no errors.
+3. Reinstall your plugins.
+
 ### Builder
 + Add capability to specify images used as a cache source on build. These images do not need to have local parent chain and can be pulled from other registries [#26839](https://github.com/docker/docker/pull/26839)
 + (experimental) Add option to squash image layers to the FROM image after successful builds [#22641](https://github.com/docker/docker/pull/22641)