Hi Roland,
Thanks a lot for your answer. I think that there is a wrong link in your "qsa-0527201" update instructions web page.
The link mentioned there is the following: https://docs.qlustar.com/en-US/Qlustar_Cluster_OS/11.0/html-single/Administr...
In this chapter there is no information about the migration to Grub PXE booting.
Now, I understand better the mentions to points 7 and 11, which I could not find :).
Thanks again.
Stephanie