红帽老版本下载地址
redhat
ftp://archive.download.redhat.com/pub/redhat/linux/ has every released version of RedHat.
ftp://distrib-coffee.ipsl.jussieu.fr/pub/linux/ has a grabbag of old-ish releases.
http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/RedHat-CD-HOWTO.html
fedora
https://dl.fedoraproject.org/pub/archive/fedora/linux/releases/
centos
https://wiki.centos.org/Download centos old versions
http://vault.centos.org/
debian
http://cdimage.debian.org/cdimage/archive/
http://archive.debian.org/debian-archive/ has every released version of Debian. Both have sources, binaries and installation floppy images but not isos.
http://snapshot.debian.org/ has almost every package that went through Debian unstable since March 2005.
ubuntu
http://old-releases.ubuntu.com/releases/ has all out-of-support releases of Ubuntu.