Comando está errado ou certo?

E ai galera alguem pode me ajuar, ao digitar o comando sudo apt-get update, ocorreu o seguinte erro abaixo especificado, porquê?


Err http://uk.archive.ubuntu.com edgy Release.gpg
Could not resolve 'uk.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty Release.gpg
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty-updates Release.gpg
Could not resolve 'br.archive.ubuntu.com'
Err http://security.ubuntu.com feisty-security Release.gpg
Could not resolve 'security.ubuntu.com'
Ign http://br.archive.ubuntu.com feisty Release
Ign http://security.ubuntu.com feisty-security Release
Ign http://br.archive.ubuntu.com feisty-updates Release
Ign http://security.ubuntu.com feisty-security/main Packages
Ign http://security.ubuntu.com feisty-security/restricted Packages
Ign http://security.ubuntu.com feisty-security/main Sources
Ign http://security.ubuntu.com feisty-security/restricted Sources
Ign http://security.ubuntu.com feisty-security/universe Packages
Ign http://security.ubuntu.com feisty-security/universe Sources
Ign http://security.ubuntu.com feisty-security/multiverse Packages
Ign http://security.ubuntu.com feisty-security/multiverse Sources
Err http://security.ubuntu.com feisty-security/main Packages
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/restricted Packages
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/main Sources
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/restricted Sources
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/universe Packages
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/universe Sources
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/multiverse Packages
Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com feisty-security/multiverse Sources
Could not resolve 'security.ubuntu.com'
Ign http://uk.archive.ubuntu.com edgy Release
Ign http://uk.archive.ubuntu.com edgy/universe Packages
Ign http://uk.archive.ubuntu.com edgy/universe Sources
Err http://uk.archive.ubuntu.com edgy/universe Packages
Could not resolve 'uk.archive.ubuntu.com'
Err http://uk.archive.ubuntu.com edgy/universe Sources
Could not resolve 'uk.archive.ubuntu.com'
Ign http://br.archive.ubuntu.com feisty/main Packages
Ign http://br.archive.ubuntu.com feisty/restricted Packages
Ign http://br.archive.ubuntu.com feisty/main Sources
Ign http://br.archive.ubuntu.com feisty/restricted Sources
Ign http://br.archive.ubuntu.com feisty/universe Packages
Ign http://br.archive.ubuntu.com feisty/universe Sources
Ign http://br.archive.ubuntu.com feisty/multiverse Packages
Ign http://br.archive.ubuntu.com feisty/multiverse Sources
Ign http://br.archive.ubuntu.com feisty-updates/main Packages
Ign http://br.archive.ubuntu.com feisty-updates/restricted Packages
Ign http://br.archive.ubuntu.com feisty-updates/main Sources
Ign http://br.archive.ubuntu.com feisty-updates/restricted Sources
Err http://br.archive.ubuntu.com feisty/main Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/restricted Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/main Sources
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/restricted Sources
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/universe Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/universe Sources
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/multiverse Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty/multiverse Sources
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty-updates/main Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty-updates/restricted Packages
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty-updates/main Sources
Could not resolve 'br.archive.ubuntu.com'
Err http://br.archive.ubuntu.com feisty-updates/restricted Sources
Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://uk.archive.ubuntu.com/ubuntu/dists/edgy/Release.gpg Could not resolve 'uk.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/Release.gpg Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty-updates/Release.gpg Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/Release.gpg Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/main/binary-i386/Packages.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/restricted/binary-i386/Packages.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/main/source/Sources.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/restricted/source/Sources.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/universe/binary-i386/Packages.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/universe/source/Sources.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/multiverse/binary-i386/Packages.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/dists/feisty-security/multiverse/source/Sources.gz Could not resolve 'security.ubuntu.com'
Failed to fetch http://uk.archive.ubuntu.com/ubuntu/dists/edgy/universe/binary-i386/Packages.gz Could not resolve 'uk.archive.ubuntu.com'
Failed to fetch http://uk.archive.ubuntu.com/ubuntu/dists/edgy/universe/source/Sources.gz Could not resolve 'uk.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/main/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/restricted/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/main/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/restricted/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/universe/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/universe/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/multiverse/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty/multiverse/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty-updates/main/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty-updates/restricted/binary-i386/Packages.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty-updates/main/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/feisty-updates/restricted/source/Sources.gz Could not resolve 'br.archive.ubuntu.com'
Reading package lists... Done
E: Some index files failed to download, they have been ignored, or old ones used instead.

Cara
Parece que seu DNS está errado, se você está usando o Speedy coloca os seguintes DNS: 200.204.0.10 e 200.204.0.138 .
e faça um teste de ping .
ping www.vivaolinux.com.br e ve se responde.
Falou !

provavelmente você deve estar atrás de um proxy, basta apenas informar o endereço do proxy.
export http://meuproxy:porta
isso deve resolver...
Jesus te abençoe!!