apt-get update não funciona e não consigo adicionar repositórios [duplicados]

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Esta pergunta já tem uma resposta aqui:

    

•              'apt-get update' não consegue encontrar servidores Ubuntu                                      13 respostas                          
        
•              Apt-Get Update: falha ao buscar; não é possível conectar-se a nenhuma fonte                                      5 respostas                          
    

Pessoal, por favor, ajude Sudo apt-get update não está funcionando e não posso adicionar nenhum repositório, obrigado.

hashik@Hashik:~$ sudo apt-get update
[sudo] password for hashik: 
Err:1 http://in.archive.ubuntu.com/ubuntu yakkety InRelease
  Could not resolve 'in.archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu yakkety-security InRelease
  Could not resolve 'security.ubuntu.com'
Err:3 http://ppa.launchpad.net/noobslab/apps/ubuntu yakkety InRelease
  Could not resolve 'ppa.launchpad.net'
Err:4 http://in.archive.ubuntu.com/ubuntu yakkety-updates InRelease
  Could not resolve 'in.archive.ub        hashik@Hashik:~$ sudo apt-get update
[sudo] password for hashik: 
Err:1 http://in.archive.ubuntu.com/ubuntu yakkety InRelease
  Could not resolve 'in.archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu yakkety-security InRelease
  Could not resolve 'security.ubuntu.com'
Err:3 http://ppa.launchpad.net/noobslab/apps/ubuntu yakkety InRelease
  Could not resolve 'ppa.launchpad.net'
Err:4 http://in.archive.ubuntu.com/ubuntu yakkety-updates InRelease
  Could not resolve 'in.archive.ubuntu.com'
Err:5 http://in.archive.ubuntu.com/ubuntu yakkety-backports InRelease
  Could not resolve 'in.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety-updates/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety-backports/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/yakkety-security/InRelease  Could not resolve 'security.ubuntu.com'
W: Failed to fetch http://ppa.launchpad.net/noobslab/apps/ubuntu/dists/yakkety/InRelease  Could not resolve 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.untu.com'
Err:5 http://in.archive.ubuntu.com/ubuntu yakkety-backports InRelease
  Could not resolve 'in.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety-updates/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/yakkety-backports/InRelease  Could not resolve 'in.archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/yakkety-security/InRelease  Could not resolve 'security.ubuntu.com'
W: Failed to fetch http://ppa.launchpad.net/noobslab/apps/ubuntu/dists/yakkety/InRelease  Could not resolve 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.