We can get MD5 of a file by using md5sum so my questions are:
Could the MD5 be changed?
How to change the MD5?
Best Answer
md5sum calculates and verifies 128-bit MD5 hashes. The MD5 hash functions as a compact digital fingerprint of a file. It is very unlikely that any two non-identical files in the real world will have the same MD5 hash, unless they have been specifically created to have the same hash.
md5sum is used to verify the integrity of files, as virtually any change to a file will cause its MD5 hash to change. Most commonly, md5sum is used to verify that a file has not changed as a result of a faulty file transfer, a disk error or non-malicious meddling.
No. You can not change md5sum of a file as long as the contents of the files are same. And that is the sole purpose of it. You can change the md5sum value of a file by making any change in its content only.
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 As a result, you were getting out-of-date versions.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.
Best Answer
md5sumcalculates and verifies 128-bit MD5 hashes. The MD5 hash functions as a compact digital fingerprint of a file. It is very unlikely that any two non-identical files in the real world will have the same MD5 hash, unless they have been specifically created to have the same hash.md5sumis used to verify the integrity of files, as virtually any change to a file will cause its MD5 hash to change. Most commonly,md5sumis used to verify that a file has not changed as a result of a faulty file transfer, a disk error or non-malicious meddling.For more see Wikipedia