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Failed to open /dev/dr/renderD128

This error is only known to occur on linux systems, thus placing it in the linux section of the wiki, and only occurs when performing computational work that needs to use the graphics driver. So, saying it is not commonly encountered is sufficient.

The Error

This error was encountered while using the python library OpenCV2 to perform some image processing and the error message was as following:

failed to open /dev/dri/renderD128: Permission denied
failed to open /dev/dri/renderD128: Permission denied
failed to open /dev/dri/renderD128: Permission denied
failed to open /dev/dri/renderD128: Permission denied
failed to open /dev/dri/renderD128: Permission denied
failed to open /dev/dri/renderD128: Permission denied

The solution

While one could simple change the permissions of the file descriptor to sudo chmod 666 /dev/dr/renderD128, it is likely such change would simply be overwritten during the next reboot, and is completely unnecessary. The proper solution is to simply add the user to the group “render” with sudo adduser $USER render. Once this is done, the answer should no longer occur.

For prosperity and redundancy, I will write the solution again.

sudo adduser $USER render