apt-get

Oi, como se faz isso? Sou novato em linux...

sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
$sudo gedit /etc/apt/sources.list

Feito isso, substitua o conteudo por este:

## Add comments (##) in front of any line to remove it from being checked.
## Use the following sources.list at your own risk.

deb http://archive.ubuntu.com/ubuntu gutsy main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu gutsy main restricted universe multiverse

## MAJOR BUG FIX UPDATES produced after the final release
deb http://archive.ubuntu.com/ubuntu gutsy-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu gutsy-updates main restricted universe multiverse

## UBUNTU SECURITY UPDATES
deb http://security.ubuntu.com/ubuntu gutsy-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu gutsy-security main restricted universe multiverse

## BACKPORTS REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://archive.ubuntu.com/ubuntu gutsy-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu gutsy-backports main restricted universe multiverse

## PLF REPOSITORY (Unsupported. May contain illegal packages. Use at own risk.)
deb http://packages.freecontrib.org/ubuntu/plf/ gutsy free non-free
deb-src http://packages.freecontrib.org/ubuntu/plf/ gutsy free non-free
deb http://packages.freecontrib.org/ubuntu/freecontrib/ gutsy free non-free
deb-src http://packages.freecontrib.org/ubuntu/freecontrib/ gutsy free non-free

agora atualiza:


$sudo aptitude update

depois instala o que deseja

sudo apt-get update

Acho que falta só o 'sudo'

Já dei o sudo