If when attempting to update software or install new software in Ubuntu you find yourself being asked to insert the installation/live CD or if you find the following errors while trying to update your sources the following should help fix this error.
W: Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognised by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/main/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognised by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/restricted/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognised by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/restricted/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognised 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.
In order to fix this you’ll need to open up a terminal and type:
sudo nano /etc/apt/sources.list
Now you’ll see something similar to the following:
From here add a # to any lines starting with “deb cdrom:” then save and exit nano (Ctrl+X, Y, Enter).
Now from terminal type:
sudo apt-get update
You should now be able to install and update all the things without the need for a CD being mounted.