anchor.diff:      "ftp://ftp.funet.fi/pub/mirrors/ftp.debian.org/debian/"
     ];
   
  -  # Ubuntu.
  -  ubuntu = [
  -    "https://nl.archive.ubuntu.com/ubuntu/"
  -    "https://old-releases.ubuntu.com/ubuntu/"
  -    "https://mirrors.edge.kernel.org/ubuntu/"
  -    "http://de.archive.ubuntu.com/ubuntu/"
  -    "http://archive.ubuntu.com/ubuntu/"
  -  ];
  -
  -  # Fedora (please only add full mirrors that carry old Fedora distributions as well).
  -  # See: https://mirrors.fedoraproject.org/publiclist (but not all carry old content).
  +  # Fedora
  +  # Please add only full mirrors that carry old Fedora distributions as well
  +  # See: https://mirrors.fedoraproject.org/publiclist (but not all carry old content)
     fedora = [
       "https://archives.fedoraproject.org/pub/fedora/"
       "https://fedora.osuosl.org/"
  
positive.code: {
  
    # Content-addressable Nix mirrors.
    hashedMirrors = [
      "https://tarballs.nixos.org"
    ];
  
negative.code:     "http://ftp.hosteurope.de/mirror/ftp.opensuse.org/discontinued/"
    ];
  
    # Ubuntu
    ubuntu = [
      "https://nl.archive.ubuntu.com/ubuntu/"
      "https://old-releases.ubuntu.com/ubuntu/"
      "https://mirrors.edge.kernel.org/ubuntu/"
      "http://de.archive.ubuntu.com/ubuntu/"
      "http://archive.ubuntu.com/ubuntu/"
    ];
  
    # ... and other OSes in general
  
    # OpenBSD
    openbsd = [
      "https://ftp.openbsd.org/pub/OpenBSD/"
      "ftp://ftp.nluug.nl/pub/OpenBSD/"
      "ftp://ftp-stud.fht-esslingen.de/pub/OpenBSD/"
    ];
  }
  