Since the suid bit on executables only changes the effective UID (EUID) the executable will run as, and not the real UID (RUID) which getuid() returns, and in addition to the restriction on suid interpreted scripts (any executable beginning with “#!“), some shells like bash as an extra safety measure will set the EUID back … Read more
There are two cases, You want to temporarily drop root privilege while executing setuid program You want to permanently drop root privilege while executing setuid program… You can temporarily do it by setting the euid to the real user id and then changing the uid to anything you want.And later when you need the root … Read more
Since you mentioned a daemon, I can conclude that you are running on a Unix-like operating system. This matters, because how to do this depends on the kind operating system. This answer applies only to Unix, including Linux, and Mac OS X. Define a function that will set the gid and uid of the running … Read more