There are two places I go when I want to download Ubuntu installer images:
Both of these appear equally official: they are both subdomains of
ubuntu.com, and the main Ubuntu website makes references to both for its download links. (http://www.ubuntu.com/download/alternative-downloads uses the former for its 'Network installer' download links, and the latter for its 'BitTorrent' download links, for example.)
If I visit http://releases.ubuntu.com/ and follow links for the current Ubuntu release, I reach a page that lists numerous links to desktop and server installer images. Likewise, if I visit http://cdimage.ubuntu.com/ and follow links in a similar manner, I get to another very similar page that also gives numerous links to desktop and server installer images. At the moment, these pages are:
(Following '14.04' links instead of 'trusty' leads to pages identical to the above, aside from their URLs.)
The language used on those two pages suggests that each page lists all of the available image files. For example, they each say "A full list of available files, including BitTorrent files, can be found below", and they each provide a wide variety of link types (
Neither page makes any reference to the other page's existence, and for a long time I thought that these were simply two different URLs serving essentially the same list of installer images.
Now that I look more closely I see that, despite appearances, the actual lists of files are almost entirely different. For the Trusty release,
amd64 images, whilst the
cdimage site serves PowerPC and Mac-friendly images. Even going back to the Precise release, when the architectures overlapped more, there are still installer images on each page that are not available from the other.
I've searched for explanations as to why the two sites are so disjoint, but have so far found none.
I assume that
releases.ubuntu.com is intended to hold the more common installer images, whilst
cdimage.ubuntu.com is intended to be a more comprehensive archive, given that it also hosts installers for the various spins such as Lubuntu, Xubuntu, etc.
However, this still doesn't explain some things:
Why is there no single page I can go to and see all available images? For example, if
releases.ubuntu.comis reserved for the more popular images, why are these not also included in the (more comprehensive) list at
If there's a good reason for keeping them separate, then why does neither page acknowledge the other as a complementary source of installer images?
Is there any historical reason for this split?
If anyone has any behind-the-scenes insight into this, I'd be interested to hear how things ended up this way.