I use Ubuntu 12.04. Today I tried to burn an ISO file in a DVD-R disk using K3b. It used to work, but today, after one and a half minutes, it stopped saying that "cdrecord has no permission to open the device". I searched for a solution, and I found that I had to do something with k3bsetup. I tried to use it, but I had no idea what to do, and I couldn't find a guide, so I checked cdrecord and clicked apply. Now there is another error; it says "cdrecord returns an unknown error! (code 254)". What should I do?