Error with fornt when running venv code as root user -- Similar to #1682

[ElBertrando]

As venv is required for Debian 12 in my Pi 4 model B, I found I can run the code by directing the file path to the virtual env ---> /home/pi/Code/SignEnv/bin/python3 /home/pi/Code/Main.py. Code runs fine but I see the message in terminal to run code as root: -->_Can't set realtime thread priority=99: Operation not permitted. You are probably not running as root ? This will seriously mess with color stability and flicker of the matrix. Please run as root (e.g. by invoking this program with sudo), or setting the capability on this binary by calling sudo setcap 'cap_sysnice=eip' /usr/bin/python3.11

However when I run as root --> sudo /home/pi/Code/SignEnv/bin/python3 /home/pi/Code/Main.py there is the font error -->

File"graphics.pyx", line 32, in rgbmatrix.graphics.Font.LoadFont Exception: Couldn't load font /home/pi/rpi-rgb-led-matrix/fonts/10x20.bdf

I tried enabling in the font directory -->chmod a+r 10x20.bdf to no avail.

[hzeller]

Do you really have an underscore at the end of the filename ?

[ElBertrando]

No that's a copy and past error --- I'll edit that out now :) -- I should also note that I had trouble importing the rgbmatix package into my virtual environment after activation and importing via the pip3 install -r requirements.txt method; But got around that by navigating to the virtual environment directory, edit the file pyvenv.cfg. Set the parameterinclude-system-site-packages = true

[hzeller]

The Exception still shows an underscore but at a different place :)

To double-check, I'd copy the message you get from the Exception and check if the file actualy is readable (which I suspect it is not with that underscore):

ls -l /home/pi/rpi-rgb-led-matrix/fonts/10x_20.bdf

Also, the good old running sudo strace -f <program> to see what is actually going on in the system might help narrow down what is going on.

[ElBertrando]

As I was on vacation, I am getting back to this issue; The underscore was a typo [I had it in two places - I've fixed the other reference]. I have verified that the file exists with ls -l /home/pi/rpi-rgb-led-matrix/fonts/10x20.bdf. A stack trace by program name sudo strace -f python3 I see the following section repeated - not sure what is means:

pselect6(1, [0], NULL, NULL, NULL, NULL) = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGWINCH {si_signo=SIGWINCH, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]})                 = -1 EINTR (Interrupted system call)
ioctl(0, TIOCGWINSZ, {ws_row=28, ws_col=111, ws_xpixel=85, ws_ypixel=0}) = 0
>>> )            = 9

[hzeller]

The question is if not your user but the drop privilege user can read the file, so you need to switch to that user first:

sudo -u daemon ls -l /home/pi/rpi-rgb-led-matrix/fonts/10x20.bdf

# Or even better to see if the content can be read
sudo -u daemon cat /home/pi/rpi-rgb-led-matrix/fonts/10x20.bdf

[ElBertrando]

Interesting -- even as root Permission denied:

[hzeller]

not as root, as daemon, as you switch to be that user (look at that command line again)

This is why I am saying you need to make sure that all directories in the path can be changed into by the user

Something like

for f in /home /home/pi /home/pi/rpi-rgb-led-matrix /home/pi/rpi-rgb-led-matrix/fonts ; do
   chmod a+rx $f
done
chmod a+r /home/pi/rpi-rgb-led-matrix/fonts/10x20.bdf

[ElBertrando]

I tried this but :

However this did work:

sudo chmod a+r /home/pi/rpi-rgb-led-matrix/fonts

[hzeller]

so, you got it to work ?

[ElBertrando]

Yes -- thx for all of the help -- I will close it now