This seems normal. As a normal user you shouldn't be able to write files out to anything in /etc like that. Precede the mv command with a sudo. i.e.: sudo mv /home/user/MyDocs/Downloads/mymoves.list /etc/apt/sources.list.d/ (You don't need to retype the filename at the end, if the destination is a folder... and to be safe, end the folder name with a / so you can get notified whether it had properly put it into an existing directory or else it'll create a FILE with the name sources.list.d if you don't.) Again, hope that helps. Seems like common Linuxy stuff, so far.