Document what is sent in checkpoint request

site/installing-weave.md

@@ -31,12 +31,20 @@ With Weave Net downloaded onto your VMs or hosts, you are ready to launch a Weav
 Weave Net [periodically contacts Weaveworks servers for available
 versions](https://github.com/weaveworks/go-checkpoint).  New versions
 are announced in the log and in [the status
-summary](/site/troubleshooting.md#weave-status).  To disable this
-check, run the following before launching Weave Net:
+summary](/site/troubleshooting.md#weave-status).
+
+The information sent in this check is:
+
+ * Host UUID hash
+ * Kernel version
+ * Docker version
+ * Weave Net version
+ * Network mode, e.g. 'awsvpc'
+
+To disable this check, run the following before launching Weave Net:
 
     export CHECKPOINT_DISABLE=1
 
-
 ###Guides for Specific Platforms
 
 CoreOS users see [here](/guides/networking-docker-containers-with-weave-on-coreos/) for an example of installing Weave using cloud-config.