W:The repository 'cdrom://Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801) 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(

manpage for repository creation and user configuration details., W:The repository '
http://archive.ubuntu.com/ubuntu 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(

manpage for repository creation and user configuration details., W:The repository '
http://archive.ubuntu.com/ubuntu xenial-updates 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(

manpage for repository creation and user configuration details., W:The repository '
http://archive.ubuntu.com/ubuntu xenial-backports 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(

manpage for repository creation and user configuration details., W:The repository '
http://archive.ubuntu.com/ubuntu xenial-security 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(

manpage for repository creation and user configuration details., E:Failed to fetch cdrom://Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801)/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:Failed to fetch
http://archive.ubuntu.com/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found, E:Failed to fetch
http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/Packages 404 Not Found, E:Failed to fetch
http://archive.ubuntu.com/ubuntu/dists/xenial-backports/main/binary-amd64/Packages 404 Not Found, E:Failed to fetch
http://archive.ubuntu.com/ubuntu/dists/xenial-security/main/binary-amd64/Packages 404 Not Found, E:Some index files failed to download. They have been ignored, or old ones used instead.