/home/# apt-get update
Ign http://archive.ubuntu.com quantal Release.gpg
Ign http://security.ubuntu.com quantal-security Release.gpg
Ign http://security.ubuntu.com quantal-security Release
Ign http://archive.ubuntu.com quantal-updates Release.gpg
Ign http://security.ubuntu.com quantal-security/main amd64 Packages/DiffIndex
Ign http://archive.ubuntu.com quantal Release
Ign http://archive.ubuntu.com quantal-updates Release
Ign http://archive.ubuntu.com quantal/main amd64 Packages/DiffIndex
Ign http://archive.ubuntu.com quantal/universe amd64 Packages/DiffIndex
Ign http://archive.ubuntu.com quantal-updates/main amd64 Packages/DiffIndex
Ign http://archive.ubuntu.com quantal-updates/universe amd64 Packages/DiffIndex
Ign http://security.ubuntu.com quantal-security/main Translation-en_US
Ign http://security.ubuntu.com quantal-security/main Translation-en
Err http://security.ubuntu.com quantal-security/main amd64 Packages
  404  Not Found [IP: 91.189.92.200 80]
Ign http://archive.ubuntu.com quantal/main Translation-en_US
Ign http://archive.ubuntu.com quantal/main Translation-en
Ign http://archive.ubuntu.com quantal/universe Translation-en_US
Ign http://archive.ubuntu.com quantal/universe Translation-en
Ign http://archive.ubuntu.com quantal-updates/main Translation-en_US
Ign http://archive.ubuntu.com quantal-updates/main Translation-en
Ign http://archive.ubuntu.com quantal-updates/universe Translation-en_US
Ign http://archive.ubuntu.com quantal-updates/universe Translation-en
Err http://archive.ubuntu.com quantal/main amd64 Packages
  404  Not Found [IP: 91.189.92.201 80]
Err http://archive.ubuntu.com quantal/universe amd64 Packages
  404  Not Found [IP: 91.189.92.201 80]
Err http://archive.ubuntu.com quantal-updates/main amd64 Packages
  404  Not Found [IP: 91.189.92.201 80]
Err http://archive.ubuntu.com quantal-updates/universe amd64 Packages
  404  Not Found [IP: 91.189.92.201 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/quantal-security/main

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal/main/binary-am

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal/universe/binar

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-updates/main/b

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-updates/univer

E: Some index files failed to download. They have been ignored, or old ones used

 

The problem is as follow;

Ubuntu 12.10 has reached End Of Life and is no longer supported. Ubuntu has remove it from their official mirrors.

 

You can change a word quantal to precise in /etc/apt/sources.list