done via calls to seteuid (2), setreuid (2), or setresuid (2). A set-group ... process's filesystem user (group) ID. setreuid (2) ( setregid (2)) Modify the process's realused in several interfaces (e.g., setreuid (2)) as a way to specify "no user ... system calls include setuid (2), setfsuid (2), setreuid (2), and setresuid (2). For groupsetegid (2), seteuid (2), setregid (2), setreuid (2), setresgid (2), setresuid (2), and setgroupsarbitrary manipulations of process UIDs ( setuid (2), setreuid (2), setresuid (2), setfsuid (2)); • forge