access and faccessat Functions
As we described earlier,when we open a file, the kernel performs its access tests based
on the effective user and group IDs. Sometimes, however,a process wants to test
accessibility based on the real user and group IDs. This is useful when a process is
running as someone else, using either the set-user-ID or the set-group-ID feature. Even
though a process might be set-user-ID to root, it might still want to verify that the real
user can access a given file. The access and faccessat functions base their tests on
the real user and group IDs. (Replace effective with real in the four steps at the end of
Section 4.5.)

 

이게 문맥이고, 여기서 Even though a process might be set-user-ID to root 이 부분이 해석이 안되는데, 비록 프로세스가 루트에 대한 set-user-ID라 해도?? 이게 무슨뜻이야 프로세스가 어떻게 set-user-ID가 될 수 있어???