Удален файл apt sources.list

## The main officially supported repository
deb http://archive.ubuntu.com/ubuntu/ lucid main restricted
deb-src http://archive.ubuntu.com/ubuntu/ lucid main restricted
deb http://archive.ubuntu.com/ubuntu/ lucid-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu/ lucid-updates main restricted

## Unsupported open source software
deb http://archive.ubuntu.com/ubuntu/ lucid universe
deb-src http://archive.ubuntu.com/ubuntu/ lucid universe
deb http://archive.ubuntu.com/ubuntu/ lucid-updates universe
deb-src http://archive.ubuntu.com/ubuntu/ lucid-updates universe

## Unsupported software of questonable license status (not open source)
deb http://archive.ubuntu.com/ubuntu/ lucid multiverse
deb-src http://archive.ubuntu.com/ubuntu/ lucid multiverse
deb http://archive.ubuntu.com/ubuntu/ lucid-updates multiverse
deb-src http://archive.ubuntu.com/ubuntu/ lucid-updates multiverse

## Security updates repository
deb http://security.ubuntu.com/ubuntu lucid-security main restricted
deb-src http://security.ubuntu.com/ubuntu lucid-security main restricted
deb http://security.ubuntu.com/ubuntu lucid-security universe
deb-src http://security.ubuntu.com/ubuntu lucid-security universe
deb http://security.ubuntu.com/ubuntu lucid-security multiverse
deb-src http://security.ubuntu.com/ubuntu lucid-security multiverse

Вы также можете рассмотреть возможность добавления следующих разделов (но если вы не знаете, что они, вероятно, лучше держаться подальше):

## The backports repository
deb http://archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse

## Canonical's partner repository
deb http://archive.canonical.com/ubuntu lucid partner
deb-src http://archive.canonical.com/ubuntu lucid partner

## Medibuntu
deb http://packages.medibuntu.org/ lucid free non-free
deb-src http://packages.medibuntu.org/ lucid free non-free

Для этого есть действительно полезный сайт.

http://repogen.simplylinux.ch/

все ответы на этом подвергают сомнению, устарели к настоящему времени, который логичен.

Если Вы все еще используете старый выпуск (Ubuntu <12.04) и все еще хотите добраться, обновления, использующие склонный - добираются, используют следующий source.list файл:

deb http://old-releases.ubuntu.com/ubuntu/ oneiric main
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric main
deb http://old-releases.ubuntu.com/ubuntu/ oneiric-updates main
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric-updates main
deb http://old-releases.ubuntu.com/ubuntu/ oneiric universe
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric universe
deb http://old-releases.ubuntu.com/ubuntu/ oneiric-updates universe
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric-updates universe
deb http://old-releases.ubuntu.com/ubuntu oneiric-security main
deb-src http://old-releases.ubuntu.com/ubuntu oneiric-security main
deb http://old-releases.ubuntu.com/ubuntu oneiric-security universe
deb-src http://old-releases.ubuntu.com/ubuntu oneiric-security universe

src

Вот файл sources.list с работающего сервера:

# deb cdrom:[Ubuntu 10.04 LTS _Lucid Lynx_ - Release i386 (20100429)]/ lucid main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://es.archive.ubuntu.com/ubuntu/ lucid main restricted
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://es.archive.ubuntu.com/ubuntu/ lucid-updates main restricted
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid-updates main restricted

## 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.
deb http://es.archive.ubuntu.com/ubuntu/ lucid universe
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid universe
deb http://es.archive.ubuntu.com/ubuntu/ lucid-updates universe
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid-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://es.archive.ubuntu.com/ubuntu/ lucid multiverse
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid multiverse
deb http://es.archive.ubuntu.com/ubuntu/ lucid-updates multiverse
deb-src http://es.archive.ubuntu.com/ubuntu/ lucid-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## 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://es.archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse
# deb-src http://es.archive.ubuntu.com/ubuntu/ lucid-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
## 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://es.archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse
# deb-src http://es.archive.ubuntu.com/ubuntu/ lucid-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 lucid partner
# deb-src http://archive.canonical.com/ubuntu lucid partner

deb http://security.ubuntu.com/ubuntu lucid-security main restricted
deb-src http://security.ubuntu.com/ubuntu lucid-security main restricted
deb http://security.ubuntu.com/ubuntu lucid-security universe
deb-src http://security.ubuntu.com/ubuntu lucid-security universe
deb http://security.ubuntu.com/ubuntu lucid-security multiverse
deb-src http://security.ubuntu.com/ubuntu lucid-security multiverse

Обратите внимание, что в этом списке используются испанские серверы. Вы должны настроить его в соответствии с вашим местоположением.