Note well expressed TODO: The idea is that on failure the permission bits, owner and groups as well as you group membership should be read to determine why your are not able to open it and give a good explaination why you cannot use it. For example, the sysadmin might have given you membership to video but have change the permissions so that only root can get access to the graphics card as it can change monitor resolution which for example some schools (for some reason I do not understand) remove that permission from you.