Running as root

[matzeema]

I'm currently trying to build a own library to communicate with the GPIOs to use UART and PWM. I am using the wiringPi library because it supports both interfaces. The problem is that wiringPi needs root permission to initialize PWM. I already searched for other solutions to run wiringPi without root but didn't find a lot.

So I just came to the point to run flutter-pi as root which doesn't seem to work.

pi@raspberrypi:~/projects/kart_project $ sudo flutter-pi .
sudo: flutter-pi: command not found

I was extra confused when I read this in README.md at the Fixing the GPU permissions part:

Otherwise, you'll need to run flutter-pi with sudo.

So is this a problem of flutter-pi or is there something wrong with my machine?

[DisDis]

use:
sudo ./flutter-pi .

[DisDis]

But you should exec (one time)
sudo usermod -a -G render pi
afte that we can exec just (without sudo):
./flutter-pi .

[ardera]

So is this a problem of flutter-pi or is there something wrong with my machine?

Neither, it's a user error 😄

You need to remember sudo is interpreting the argument you give it as a completely different user, namely root. root has it's own user directory (/root), similiar to the pi user, which has /home/pi as its user directory.

So everything you put into /home/pi/.bashrc, /home/pi/.profile or /home/pi/bin (et al.) will not work when using sudo. (Because the shell looks for these file in /root instead). So in your case, you probably put the path to flutter-pi into your PATH variable inside /home/pi/.bashrc, or you created a symlink in /home/pi/bin to point to the flutter-pi executable, so you don't have to invoke flutter-pi with the path every time. But this does not work when running using sudo.

You need to use the path of the flutter-pi executable when running using sudo. So for example, sudo ./flutter-pi or sudo /home/pi/devel/flutter-pi. Or you modify the .bashrc or similiar of the root user, but that may be a security hazard.

[matzeema]

Oh thank you! I am quite new to Linux so thanks for the explanation. Works fine :)