Primeiro, você precisa editar ou criar seu arquivo /etc/apt/sources.list , portanto, execute o seguinte comando:
sudo nano /etc/apt/sources.list
Agora, copie e cole o seguinte conteúdo no terminal:
# deb cdrom:[Ubuntu-Studio 16.04 LTS _Xenial Xerus_ - Alpha amd64 (20151225)]/ xenial main multiverse restricted universe
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://archive.ubuntu.com/ubuntu/ xenial main restricted
deb-src http://archive.ubuntu.com/ubuntu/ xenial main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://archive.ubuntu.com/ubuntu/ xenial universe
deb-src http://archive.ubuntu.com/ubuntu/ xenial universe
deb http://archive.ubuntu.com/ubuntu/ xenial-updates universe
deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://archive.ubuntu.com/ubuntu/ xenial multiverse
deb-src http://archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://archive.ubuntu.com/ubuntu/ xenial-updates multiverse
deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu xenial partner
deb-src http://archive.canonical.com/ubuntu xenial partner
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse
deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
Pressione CTRL + o e depois pressione ENTER para salvar o arquivo. Pressione CTRL + x para sair do nano.
Quando isso for feito, execute o seguinte comando:
sudo apt-get update
E para aplicar qualquer atualização, execute um dos seguintes comandos:
sudo apt-get upgrade
ou
sudo apt-get dist-upgrade