السلام عليكم

لتقوم يهذا التحديث قم بتعدي ملف sources.list كالتالي
sudo gedit /etc/sources.list
ثم قم بحذف محتوياته و ضع التالي
# Automatically generated sources.list
# http://www.ubuntu-nl.org/source-o-matic/
#
# If you get GPG errors with this sources.list, locate the GPG key in this file
# and run these commands (where KEY is replaced with that key)
#
# gpg --keyserver hkp://subkeys.pgp.net --recv-keys KEY
# gpg --export --armor KEY | sudo apt-key add -

# Ubuntu supported packages
# GPG key: 437D05B5
deb http://us.archive.ubuntu.com/ubuntu feisty main restricted
deb http://us.archive.ubuntu.com/ubuntu feisty-updates main restricted
deb http://security.ubuntu.com/ubuntu feisty-security main restricted

deb-src http://us.archive.ubuntu.com/ubuntu feisty main restricted
deb-src http://us.archive.ubuntu.com/ubuntu feisty-updates main restricted
deb-src http://security.ubuntu.com/ubuntu feisty-security main restricted

# Ubuntu community supported packages
# GPG key: 437D05B5
deb http://us.archive.ubuntu.com/ubuntu feisty universe multiverse
deb http://us.archive.ubuntu.com/ubuntu feisty-updates universe multiverse
deb http://security.ubuntu.com/ubuntu feisty-security universe multiverse

deb-src http://us.archive.ubuntu.com/ubuntu feisty universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu feisty-updates universe multiverse
deb-src http://security.ubuntu.com/ubuntu feisty-security universe multiverse

# Ubuntu backports project
# GPG key: 437D05B5
deb http://us.archive.ubuntu.com/ubuntu feisty-backports main restricted universe multiverse

deb-src http://us.archive.ubuntu.com/ubuntu feisty-backports main restricted universe multiverse
ثم
sudo apt-get update
sudo apt-get dist-upgrade

قم بهذه العملية تحت مسؤوليتك الشخصية