Rudder

The message is:

[2016-09-30 08:55:17] ERROR com.normation.inventory.provisioning.endpoint.FusionReportEndpoint - Rejecting Inventory 
'u90tx396-8729564d-df03-477f-950d-cb21bd96278c.ocs' for Node '8729564d-df03-477f-950d-cb21bd96278c' because signature
is not valid, you can update the inventory key by running the following command 
'/opt/rudder/bin/rudder-keys change-key 8729564d-df03-477f-950d-cb21bd96278c <your new public key>'

That message doesn't give any hint to check that perhaps the node sending the inventory is not the one known be Rudder (for example if the orginal node was cloned + CFEngine Key updated, or if it's an actual attempt to alter one node inventory).

A better one could be something along:

[2016-09-30 08:55:17] ERROR com.normation.inventory.provisioning.endpoint.FusionReportEndpoint  - Rejecting Inventory  
'u90tx396-8729564d-df03-477f-950d-cb21bd96278c.ocs'  for Node '8729564d-df03-477f-950d-cb21bd96278c' because 
inventory signature wasn't done with the same CFEngine key than the one saved in Rudder for that node. If you
updated the CFEngine key of the node, you can update the one stored by Rudder with the following command: 
'/opt/rudder/bin/rudder-keys change-key  8729564d-df03-477f-950d-cb21bd96278c <your new public key>'. Else 
please check that the node sending that inventory is actually the node registered into Rudder.