当我尝试在“更新管理器”中更新我的 xubuntu 时出现此错误：
Failed to download repository information
当我尝试通过终端更新时，我得到了以下信息：
W: Failed to fetch cdrom://Xubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)/dists/precise/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://Xubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)/dists/precise/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://Xubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)/dists/precise/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://Xubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)/dists/precise/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
E: Some index files failed to download. They have been ignored, or old ones used instead.
怎么办啊？10天没更新了。