sudo apt update
Ign:1 http://de.archive.ubuntu.com/ubuntu zesty InRelease
Ign:2 http://de.archive.ubuntu.com/ubuntu zesty-updates InRelease
Ign:3 http://de.archive.ubuntu.com/ubuntu zesty-backports InRelease
Err:4 http://de.archive.ubuntu.com/ubuntu zesty Release
  404  Not Found [IP: 141.30.62.24 80]
Err:5 http://de.archive.ubuntu.com/ubuntu zesty-updates Release
  404  Not Found [IP: 141.30.62.24 80]
Err:6 http://de.archive.ubuntu.com/ubuntu zesty-backports Release
  404  Not Found [IP: 141.30.62.24 80]
Ign:7 http://security.ubuntu.com/ubuntu zesty-security InRelease
Err:8 http://security.ubuntu.com/ubuntu zesty-security Release
  404  Not Found [IP: 91.189.91.26 80]
Reading package lists... Done
E: The repository 'http://de.archive.ubuntu.com/ubuntu zesty Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://de.archive.ubuntu.com/ubuntu zesty-updates Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://de.archive.ubuntu.com/ubuntu zesty-backports Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://security.ubuntu.com/ubuntu zesty-security Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.