How can an administrator revert to a previous state of a virtual machine after an OS update?

In the context of managing virtual machines, taking a snapshot of a VM is the most effective way to revert to a previous state after an OS update. When an administrator takes a snapshot, they capture the exact state of the virtual machine at that moment, including the VM's power state, the contents of its memory, and the disk state. This allows the administrator to return to that specific state later if needed.

If the OS update leads to issues, using the snapshot feature allows for a quick recovery—simply reverting to the snapshot returns the VM to the state it was in when the snapshot was taken, effectively undoing the changes made by the update. This is a crucial tool for managing risk associated with updates, upgrades, and other changes in a virtualized environment.

The other options do not provide the same immediate ability to revert to a previously saved state. Cloning to a template or a virtual machine creates a new instantiation based on the current VM, rather than allowing direct reversion to a prior state. Migration pertains to moving a VM from one host to another and does not facilitate reverting to a previous state. Thus, utilizing snapshots is the appropriate method for restoring a VM to a prior status following an OS update.