There are classifications for operating system failures. Which of the following refers to what takes place when an unexpected kernel or media failure happens and the regular recovery procedure cannot recover the system to a more consistent state, requiring an administrator to intervene?

A.
Emergency system restart

B.
Trusted recovery

C.
System cold start

D.
System reboot

Explanation:
C: An operating system’s response to a failure can be classified as either a system reboot, an emergency system restart, or a system cold start. A system cold
start takes place when an unexpected kernel or media failure happens and the regular recovery procedure cannot recover the system to a more consistent state.
The system, kernel, and user objects may remain in an inconsistent state while the system attempts to recover itself, and intervention is commonly required by the
user or administrator to restore the system.
+ A is incorrect because an emergency system restart takes place after a system failure happens in an uncontrolled manner without the need of a person to be
involved. The failure could be a kernel or media failure caused by lower-privileged user processes attempting to access memory segments that are restricted. The
system sees this as an insecure activity that it cannot properly recover from without rebooting. The kernel and user objects could be in an inconsistent state, and
data could be lost or corrupted. The system thus reboots itself and goes into maintenance mode and recovers from the actions taken. Then it is brought back up in
a consistent and stable state.
+ B is incorrect because trusted recovery is not one of the three classifications for an operating system’s response to a type of failure. Trusted recovery is a
general term that means that when an operating system or application crashes or freezes, it should not put the system in any type of insecure state. The usual
reason for a system crash in the first place is that it encountered something it perceived as insecure or did not understand and decided it was safer to freeze, shut
down, or reboot than to perform the current activity.
+ D is incorrect because a system reboot takes place after the system shuts itself down in a controlled manner in response to a kernel (trusted computing base)
failure and does not require a person to be involved. If the system finds inconsistent object data structures, or if there is not enough space in some critical tables, a
system reboot may take place. This releases resources and returns the system to a more stable and safer state.