我无法升级到最新版本 13.04。错误是：
Failed to download repository information
Check your Internet connection.
Details
W:Failed to fetch cdrom://Ubuntu 12.10 _Quantal Quetzal_ - Release i386 (20121017.2)/dists/quantal/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 12.10 _Quantal Quetzal_ - Release i386 (20121017.2)/dists/quantal/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,
E:Some index files failed to download. They have been ignored, or old ones used instead.
答案1
在 中注释掉 cdrom 条目/etc/apt/sources.list，它很可能是文件中的第一行之一。另一种方法是使用Software sources图形工具。
答案2
执行以下命令...
sudo software-properties-gtk
在打开的窗口中，
取消选择 CD-ROM 条目，在Installable from CD-ROM/DVD
