How to erase a system disk on iMac or MacBook?
When attempting to erase the internal system disk on a Mac using Active@ KillDisk, the process may fail with multiple errors and quit unexpectedly — even if the machine was booted from an external drive. This typically happens because System Integrity Protection (SIP), a macOS security feature, blocks low-level write access to the system disk by default.
To successfully erase an internal system disk on an Apple system, you need to disable System Integrity Protection first.
Disabling SIP removes a macOS security layer that protects system files from modification. Only disable it temporarily, for the purpose of erasing the disk, and re-enable it afterward if the machine will continue to be used.
See How to turn off System Integrity Protection in macOS? for step-by-step instructions.