Hi @jmelis
Thanks a lot for your reply! about the two options that you have commented I think that we will try the first one. I assume that /var/lib/one/remotes/tm/shared/premigrate will also overwritten after a package upgrade right?.
For shared datastores it only contains an exit 0. I will include our script here.
probably you have already thought about that, to include something like a prolog and epilog scripts defined by the user not only for the migration, also for cp and mv VMM actions to be executed in the hypervisors, that would be great! I don’t know if someone else will be interested on this…
But now I will try the premigrate script 
, we can also set this file from Quattor toolkit
Cheers and thanks!
Alvaro