My upgrade using alternative iso from 11.10 to 12.04 got interrupted and I had to hard restart my machine. Now I feel that everything is recovered except my already installed packages like vim.

How do I backup my home folder for fresh installation of ubuntu? Following are the errors I'm facing

I couldn't mark any package for re-installation in synaptic or remove and install too. output of sudo apt-get install vim

Building dependency tree       
Reading state information... Done
Package vim is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'vim' has no installation candidate

If I try installing it from synaptic I get

apache2.2-common:

Package apache2.2-common has no available version, but exists in the database.
This typically means that the package was mentioned in a dependency and never uploaded, has been obsoleted or is not available with the contents of sources.list

my sources.list file

# added by the release upgrader
# deb cdrom:[Ubuntu 12.04.1 LTS _Precise Pangolin_ - Release amd64 (20120822.4)]/ precise main restricted
# added by the release upgrader
# # deb cdrom:[Ubuntu 12.04.1 LTS _Precise Pangolin_ - Release amd64 (20120822.4)]/ precise main restricted
# deb cdrom:[Ubuntu 11.04 _Natty Narwhal_ - Release amd64 (20110427.1)]/ natty main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://archive.ubuntu.com/ubuntu precise main restricted
deb-src http://archive.ubuntu.com/ubuntu precise main restricted

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

deb http://archive.ubuntu.com/ubuntu precise-security main restricted
deb-src http://archive.ubuntu.com/ubuntu precise-security main restricted
deb http://archive.ubuntu.com/ubuntu precise-security universe
deb-src http://archive.ubuntu.com/ubuntu precise-security universe
deb http://archive.ubuntu.com/ubuntu precise-security multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-security 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 precise partner
# deb-src http://archive.canonical.com/ubuntu natty 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 precise main
deb-src http://extras.ubuntu.com/ubuntu precise main
# deb http://tamil.3758_gmail.com:[email protected]/free unstable main # disabled on upgrade to oneiric
# deb http://debian.datastax.com/natty oneiric main # disabled on upgrade to oneiric

sudo apt-get update

Err http://archive.ubuntu.com precise InRelease

Err http://archive.canonical.com precise InRelease

Err http://archive.ubuntu.com precise-updates InRelease

Err http://archive.ubuntu.com precise-security InRelease

Err http://extras.ubuntu.com precise InRelease    

Err http://archive.canonical.com precise Release.gpg
  Unable to connect to 172.16.140.249:3142:
Err http://archive.ubuntu.com precise Release.gpg
  Unable to connect to 172.16.140.249:3142:
Err http://archive.ubuntu.com precise-updates Release.gpg
  Unable to connect to 172.16.140.249:3142:
Err http://extras.ubuntu.com precise Release.gpg
  Unable to connect to 172.16.140.249:3142:
Err http://archive.ubuntu.com precise-security Release.gpg
  Unable to connect to 172.16.140.249:3142:
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/precise/InRelease