An image backup, also known as a full system backup, captures the entire contents of a system, including the operating system, applications, settings, and all data. This type of backup allows for a complete recovery of the system in case of a disaster, as it includes everything needed to restore the system to its previous state.
This makes it the ideal choice for a systems administrator who needs to ensure the ability to recover the entire system, including the OS.
References = CompTIA Security+ SY0-701 study materials, domain on Security Operations.