Источники отсутствуют в /etc/apt/sources.list, как мне их вернуть?

Каким-то образом моя установка Ubuntu не может найти то, что я считаю очень распространенными пакетами ....

E: Unable to locate package php5-curl
E: Unable to locate package php5-gd

Я знаю, что это как-то связано с моими источниками, однако я не уверен, какой источник мне нужен или в какой источник эти пакеты будут включены.

Это команды, которые я выполнил

sudo apt-get install php5-curl
sudo apt-get install php5-gd

Вот содержание /etc/apt/sources.list:

# deb cdrom:[Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)]/ dists/oneiric/main/binary-i386/

# deb cdrom:[Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)]/ oneiric main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

## Major bug fix updates produced after the final release of the
## distribution.

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.

## 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.

## 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.


## 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 oneiric partner
# deb-src http://archive.canonical.com/ubuntu oneiric partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
# deb http://extras.ubuntu.com/ubuntu oneiric main
# deb-src http://extras.ubuntu.com/ubuntu oneiric main

# deb http://repository.spotify.com stable non-free