https://help.ubuntu.com/community/Repositories/CommandLine

First, save your original sources.list file.

• sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup

Now make the changes to uncomment all repositories listed in the sources.list file.

• sudo sed -i -e "s/# deb/deb/g" /etc/apt/sources.list

Сейчас разрешено всё что есть. Нужно закомментировать назад CD-ROM, чтоб не ругался:

• sudo sed -i -e "s/deb cdrom/# deb cdrom/g" /etc/apt/sources.list

Make apt aware of the new software repositories by issuing the following command:

• sudo apt-get update

Done! The new software repositories should now be available for use.