As it stands today there is little or no feedback on invalid configurations which are set with setparam.

We should check for invalid configuration entries when they're applied. This will likely be difficult with the current design so we'll need to look into how to address this.

A recent example and common mistake is when identity_upcall set to 'none' instead of 'NONE'. This results in MDS upcall forking out to 'none' executable which obviously doesn't exist and isn't desired behavior.