ace@ace-desktop:~$ sudo apt update
Err:1 http://archive.ubuntu.com/ubuntu yakkety InRelease
  Could not resolve 'archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu yakkety-security InRelease
  Could not resolve 'security.ubuntu.com'
Err:3 http://archive.ubuntu.com/ubuntu yakkety-updates InRelease
  Could not resolve 'archive.ubuntu.com'
Err:4 http://archive.ubuntu.com/ubuntu yakkety-backports InRelease
  Could not resolve 'archive.ubuntu.com'
Err:5 http://archive.ubuntu.com/ubuntu yakkety-security InRelease
  Could not resolve 'archive.ubuntu.com'
Reading package lists... Done
Building dependency tree       
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/yakkety/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/yakkety-updates/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/yakkety-backports/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/yakkety-security/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/yakkety-security/InRelease  Could not resolve 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.
ace@ace-desktop:~$