---# apt update
Err:1 http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu xenial InRelease
  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
Get:2 file:/mnt/.auto/install/repo xenial InRelease [3933 B]
Err:3 http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu xenial-updates InRelease
  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
Err:4 http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu xenial-security InRelease
  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
Err:5 http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu xenial-backports InRelease
  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
Err:6 http://archive.canonical.com xenial InRelease                              
  Temporary failure resolving 'archive.canonical.com'
Get:2 file:/mnt/.auto/install/repo xenial InRelease [3933 B]                     
Reading package lists... Done 
Building dependency tree... Done
All packages are up to date.
W: Failed to fetch http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu/dists/xenial/InRelease  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
W: Failed to fetch http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu/dists/xenial-updates/InRelease  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
W: Failed to fetch http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu/dists/xenial-security/InRelease  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
W: Failed to fetch http://ftp-stud.hs-esslingen.de/pub/Mirrors/ubuntu/dists/xenial-backports/InRelease  Temporary failure resolving 'ftp-stud.hs-esslingen.de'
W: Failed to fetch http://archive.canonical.com/dists/xenial/InRelease  Temporary failure resolving 'archive.canonical.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.