zsync can extremely reduce your download size so it's suitable for huge ISO image transfers. For your information, Ubuntu provides .zsync files for all its ISO images. You can use zsync console to get the 17.04 release without downloading from zero the whole 1.5GB. I write this article to welcome Ubuntu 17.04 Zesty Zapus soon and I hope this helps you.
What you need
- zsync program installed
- Any previous version of Ubuntu image (e.g. ubuntu-16.04-desktop-amd64.iso)
- Enough disk space for one old + one new image files
What to prepare
You need a previous version of Ubuntu image and a .zysnc URL to 17.04 image.
1) Rename the image file into exactly the same as 17.04 image filename. For example, if you have "ubuntu-desktop-16.04-amd64.iso" and you want to download ubuntu-desktop-17.04-amd64.iso, rename the "16.04" into "17.04". zsync will calculate the diff between this local file and the file on server.
2) Look for .zsync link for 17.04. You can find them at CDIMAGE or RELEASES. The URL is similar to this "http://releases.ubuntu.com/zesty/ubuntu-17.04-beta2-desktop-amd64.iso.zsync".
Note: if you don't have any Ubuntu image, just ask your friend a copy.
How to download
Run zsyc command to .zsync URL in the same directory as your local image file. It looks like this:
$ zsync http://releases.ubuntu.com/zesty/ubuntu-17.04-beta2-desktop-amd64.iso.zsync
Zsync will smartly calculate the difference size between your local and the actual 17.04 image you want to download. Then it will download only the diff size.
Once finished, zsync will automatically verify (checksum) your newly downloaded 17.04 image. And don't forget the old image will be renamed to use .zs-old extension. The actual image file you download is the one with .iso extension for example ubuntu-17.04-desktop-amd64.iso. Enjoy Ubuntu 17.04!