RHEL Linux - Red Hat System Administration Practice Exam

Which special permission allows a user to run an executable file (command) as the user of the file?

1. setuid

2. setgid

3. stickybit

4. none of the above

The correct answer is: setuid

The special permission that allows a user to run an executable file with the privileges of the owner of that file is known as setuid. When the setuid permission is set on an executable file, it grants users the ability to execute the file with the effective user ID of the file's owner, rather than their own user ID. This is particularly useful for commands that require higher privileges to perform specific tasks, such as changing passwords or accessing certain system files. For example, if a program has the setuid bit set and is owned by the root user, any user who runs this program will do so with root privileges, thereby enabling actions that they typically would not have permission to execute. This mechanism is commonly used in Unix and Linux systems to provide necessary functions while maintaining security by only allowing elevated privileges on a per-command basis. Other special permissions like setgid and sticky bit serve different purposes. Setgid allows executables to run with the effective group ID of the file's group, which is useful for shared directories. The sticky bit is used primarily on directories to prevent users from deleting files that they do not own, regardless of their write permissions. Understanding these permissions is crucial for managing security and functionality in a Linux environment.