Sempre que tento atualizar, recebo esta mensagem:
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/main/binary-amd64/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/multiverse/binary-amd64/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/restricted/binary-amd64/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/universe/binary-amd64/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/main/binary-i386/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/multiverse/binary-i386/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/restricted/binary-i386/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch cdrom://Ubuntu-GNOME 13.10 _Saucy Salamander_ - Release amd64 (20131017)/dists/saucy/universe/binary-i386/Packages
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W:Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found
W:Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/trusty/main/binary-i386/Packages 404 Not Found
E:Some index files failed to download. They have been ignored, or old ones used instead.
Embora eu tenha conexão com a internet. Qual seria o problema?
Abra o terminal CTRL + ALT + T e execute o seguinte comando:
gksu software-properties-gtk
uma pequena janela será aberta, digite sua senha de usuário, então uma janela será aberta, chamada software sources, desmarque cdrom e desmarque os dois ppas que não conseguiram buscar abaixo. 
sudo apt-get update && sudo apt-get upgrade