I am running Arch Linux on a Raspberry Pi 2.

I have a user-space program that uses Gordon's wiringPi library and, in particular, the piHiPri() function that attempts to set the highest priority for the current process (using sched_setscheduler and SCHED_RR mode). This function needs superuser privileges.

The root user is the default one when installing Arch Linux so I created a user named builder that I added to sudoers thanks to visudo.

My problem is: when I execute the program with the root user, the sched_setscheduler function returns “Operation not permitted” (getting it from errno).

If I execute it while being builder I get a “permission denied”.

However if I execute it with sudo myProgram while being builder, everything is fine and I can see that priority has changed with the top command.

I thought that the root user might not have UID 0 so I checked with id -u root but this returns 0.

ls -l myProgramm gives -rwxr-xr-x 1 root root. I also tried to set SUID with chmod +s myProgramm without success.

Any idea on how to make my program executable by root?