More zsync magic for LTS updates

I wrote before about how to update superceeded ISOs using zsync, and it's time to do that again, now that 16.04 LTS has the latest point release, to .4.

So the new command needed, after cd /path/to/iso is

cp kubuntu-16.04{.3,.4}-desktop-i386.iso && zsync http://cdimage.ubuntu.com/kubuntu/releases/16.04.4/release/kubuntu-16.04.4-desktop-i386.iso.zsync

The magic I didn't fully understand was the {.3,.4} part. Now I get that it is saying copy the files ending in .3 and replace them with files ending in .4.

I wanted also to point out that zsync is also invaluable for testing, because Ubuntu spins daily ISOs. For instance, on the qatracker such as the most recent for testing the above point releases, http://iso.qa.ubuntu.com/qatracker/milestones/386/builds there are a number of small CD icons. When you click on one, you are led to a small page with for instance, the following links to get xenial-desktop-amd64.iso:

HTTP http://cdimage.ubuntu.com/kubuntu/xenial/daily-live/20180228/xenial-desktop-amd64.iso 

RSYNC rsync -tzhhP rsync://cdimage.ubuntu.com/cdimage/kubuntu/xenial/daily-live/20180228/xenial-desktop-amd64.iso 

ZSYNC zsync http://cdimage.ubuntu.com/kubuntu/xenial/daily-live/20180228/xenial-desktop-amd64.iso.zsync 

GPG signature http://cdimage.ubuntu.com/kubuntu/xenial/daily-live/20180228/MD5SUMS.gpg 

MD5 checksum http://cdimage.ubuntu.com/kubuntu/xenial/daily-live/20180228/MD5SUMS

The http link will download via your browser to your ~/.Downloads folder unless you have set that otherwise. Fine if you want your testing ISO to be there. If instead you do zsync by

cd ~/Downloads && zsync http://cdimage.ubuntu.com/kubuntu/xenial/daily-live/20180228/xenial-desktop-amd64.iso.zsync

in the commandline, you will see a remarkable difference in how long it takes to download the second and subsequent times. Rsync does roughly the same thing. For these you do not need the "copy" cp step.

Get familiar with zysnc and use it more. It will save you time and make you more productive.

(originally posted a couple of weeks ago, but to my genealogy blog by mistake)