My guess is that this is a coding issue, and you didn’t identify how you wrote your program.
If this works in real mode, that probably should be a hint where your coding error is, the method you use to connect and use a USB device.
Yes, there are differences between a virtual tty and a real mode tty, and you’ve probably run into one of those differences.
I’d guess you might get more eyes relevant to whatever coding language you’re using if you post instead in the Programming/Scripting Forum.
And, you may want to provide a snippet of the code you use to access USB devices.
there is a misunderstanding: it is not my program that is not able to access a usb device,
it is linux itself! the program doesn’t access any usb device at all.
when I switch to kde, the mouse doesn’t work anymore, when i insert a usb stick it is
not detected…
Observe the output from dmesg (as already suggested) when a USB device is attached. When a memory stick is connected what is reported by ‘blkid’ or ‘fdisk -l’?
Re-reading your original post,
It still sounds like you are saying that your code is what you believe that triggers losing access to USB devices.
So, my previous comment about needing to inspect your application code still applies.
The suggestions to view dmesg should also be important to determine what is happening when your app launches.
Also, have you tried running your app in a real mode TTY (eg init3)?
You should do so, then switch back to a graphical console and check whether your USB devices still work.
You were asked to provide output of dmesg. Both commands require device nodes to be present; if for some reasons device nodes are not created - or you do not have permissions to access them - these commands show nothing. But dmesg shows what kernel detected.