The nice command on Linux and Unix can be used by non-root users to set a nice v

Question

The nice command on Linux and Unix can be used by non-root users to set a nice value for a process that is positive or 0, but only root (or users with the proper permission) can set a nice value that is negative. Which of the following explanations is the right one ?

A. The nice field in the kernel task structure is unsigned int and cannot accept negative values.

B. A negative nice value gives a process extended access rights to OS resources, equivalent to a switch to kernel mode. This is dangerous if available to regular users.

C. Regular users can abuse the nice command and could assign a high priority (and more CPU time) to a process possibly in detriment to system tasks .

Explanation / Answer

Answer: B

The nice field in the kernel task structure can hold unsigned and signed int value. The value can range from -20 to 19. The default nice value is 0 and lower (negative) value indicate higher priority and access to more OS resources.

Regular user do NOT have permission to increase the priority and abuse the stability of the system.

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