Making a boot drive for a first partition inaccessible to other partitions in a partitionable system

A baseboard management controller in a multi-processor system may perform operations including: causing, during a first time period, the system to operate in a partitioned state with a first partitioned node including a first subset of components of the system and a second partitioned node including a second subset of components of the system, wherein the first and second partitioned nodes are independently operable nodes having their own operating systems, and wherein the first partitioned node boots from a first boot drive that is included in the first subset; causing, during a second time period, the system to operate in a unified state with a single unified node including components from both the first and second subsets of components, wherein the single unified node has its own operating system; and causing the first boot drive to be inaccessible to the second partitioned node and the single unified node.