ubuntu14.4下载软件仓库失败

今天在linux 上执行命令行

sudo apt-get update

时出现了以下的错误信息：

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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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-Kylin 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417.1)/dists/trusty/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.

百度了好长时间才发现了问题所在



原来我把“Ｃｄｒｏｍ　ｗｉｔｈ　Ｕｂｕｎｔｕ１４．０４　‘Ｔｒｕｓｔｙ　Ｔahr’“选择了，而我没有挂载光盘　

取消选择重新运行命令行　　sudo apt-get update 得到如下结果：



不报错了

ps: 这个问题只是我遇到的，并不一定是唯一答案