Et voila:

mrbeedies@mrbeedies-laptop:/etc/apt/sources.list.d$ cat /etc/apt/sources.list
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://fr.archive.ubuntu.com/ubuntu/ feisty main restricted
deb-src http://fr.archive.ubuntu.com/ubuntu/ feisty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://fr.archive.ubuntu.com/ubuntu/ feisty-updates main restricted
deb-src http://fr.archive.ubuntu.com/ubuntu/ feisty-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://fr.archive.ubuntu.com/ubuntu/ feisty universe
deb-src http://fr.archive.ubuntu.com/ubuntu/ feisty 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://fr.archive.ubuntu.com/ubuntu/ feisty multiverse
deb-src http://fr.archive.ubuntu.com/ubuntu/ feisty 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://fr.archive.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse
# deb-src http://fr.archive.ubuntu.com/ubuntu/ feisty-backports main restricted universe multiverse

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

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

deb http://fr.archive.ubuntu.com/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://fr.archive.ubuntu.com/ubuntu edgy-updates main restricted universe multiverse

deb http://fr.archive.ubuntu.com/ubuntu/ edgy-security main restricted universe multiverse
deb-src http://fr.archive.ubuntu.com/ubuntu edgy-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ feisty-backports restricted main multiverse universe
mrbeedies@mrbeedies-laptop:/etc/apt/sources.list.d$

Sinon la commande "ls" m'a affiché:

mrbeedies@mrbeedies-laptop:/etc/apt/sources.list.d$ cd /etc/apt/sources.list.d
mrbeedies@mrbeedies-laptop:/etc/apt/sources.list.d$ ls
feisty-main.list feisty-main.list.save