sudo apt-get update E: Some index files failed to download. They have been ignored, or old ones used instead.

===========#sudo apt-get update, Error==========

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/main/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/restricted/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/universe/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/multiverse/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/main/binary-amd64/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/restricted/binary-amd64/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-amd64/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/multiverse/binary-amd64/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/main/binary-i386/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/restricted/binary-i386/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-i386/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy/multiverse/binary-i386/Packages  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy-updates/main/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy-updates/restricted/source/Sources  404  Not Found [IP: 91.189.91.24 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/saucy-updates/universe/source/Sources  404  Not Found [IP: 91.189.91.24 80]

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

======Fix======

Replace http://archive.ubuntu.com/ with http://old-releases.ubuntu.com in /etc/apt/sources.list

#sudo sed -i -e 's/archive.ubuntu.com\|security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

#sudo apt-get update