Added a note on updating older clones

Author: rjsparks

docker/README.md

@@ -156,6 +156,11 @@ On Windows:
 docker compose down -v --rmi all
 docker image prune
 ```
+### Updating an older environment
+
+If you already have a clone, such as from a previous codesprint, and are updating that clone, before starting the datatracker from the updated image:
+* rm ietf/settings_local.py   # The startup script will put a new one, appropriate to the current release, in place
+* Execute the `Clean all` sequence above.
 
 ### Accessing PostgreSQL Port
 
@@ -197,4 +202,4 @@ drwxrwxr-x   5  100999  100999    4096 May 25 07:56 client
 (etc...)
 ```
 
-Try uninstalling Docker Desktop and installing Docker Compose manually. The Docker Compose bundled with Docker Desktop is incompatible with our software. See also [Rootless Docker: file ownership changes #3343](https://github.com/lando/lando/issues/3343), [Docker context desktop-linux has container permission issues #75](https://github.com/docker/desktop-linux/issues/75).
+Try uninstalling Docker Desktop and installing Docker Compose manually. The Docker Compose bundled with Docker Desktop is incompatible with our software. See also [Rootless Docker: file ownership changes #3343](https://github.com/lando/lando/issues/3343), [Docker context desktop-linux has container permission issues #75](https://github.com/docker/desktop-linux/issues/75).