W:Target Sources (main/source/Sources) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:7, W:Target Sources (restricted/source/Sources) is configured multiple times in /etc/apt/sources.list:2 and /etc/apt/sources.list:7, W:The repository 'cdrom://Ubuntu-GNOME 16.04 LTS _Xenial Xerus_ - Release amd64 (20160421) xenial Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., W:http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg: Signature by key 4CCA1EAF950CEE4AB83976DCA040830F7FAC5991 uses weak digest algorithm (SHA1), W:http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg: Signature by key 3B068FB4789ABE4AEFA3BB491397BC53640DB551 uses weak digest algorithm (SHA1), E:Failed to fetch cdrom://Ubuntu-GNOME 16.04 LTS _Xenial Xerus_ - Release amd64 (20160421)/dists/xenial/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs, E:Some index files failed to download. They have been ignored, or old ones used instead.