I downloaded ubuntu-12.04-desktop-amd64.iso from http://releases.ubuntu.com/precise/
This page also has a link to file showing the respective MD5 hashes for each file
The page shows
128f0c16f4734c420b0185a492d92e52 *ubuntu-12.04-desktop-amd64.iso
But when I checked my downloaded ISO using the md5sum program I get
57876b3740ee89e75c8fefc93a7ceee6 *ubuntu-12.04-desktop-amd64.iso
I also downloaded the ISO via BitTorrent using
http://releases.ubuntu.com/precise/ubuntu-12.04-desktop-amd64.iso.torrent
This time using md5sum for this file shows the correct hash 128f0c16f4734c420b0185a492d92e52, but the ISO is 732MB, not 698MB as shown on the release page.
What could be happening here?
Best Answer
So, firstly, sorry for the confusion here. Fundamentally it came down to a communication glitch between the release team and our sysadmins.
Around release time, we push many of our images out to Amazon's CloudFront service to keep our bandwidth use under control. releases.ubuntu.com is managed directly by the release team, but the images on CloudFront are pushed by our sysadmins, and we have to push there well in advance to make sure everything's in place. The sysadmins pushed the most recent daily build at the time, but after that we had to respin images for some serious bugs, and we forgot to let the sysadmins know about this so that they could update CloudFront. As a result, you were getting out-of-date versions.
We've pushed updated images to CloudFront now, and all should be well, although I'm going to check things over manually just to make sure.