Syncing image

Currently there are 2 methods available to sync existing images against a current image, both enable us to only download from a server the difference between what we have locally and what exists on the server cutting down on the required bandwidth.

The first of these is in general already installed and available to use, zsync will need installing.

The following examples assume that you are currently in the same folder that the image to be synced exists in.

rsync

From the download page of the tracker copy and paste the command you see, then append the filename of the image you wish to sync.

rsync -tzhhP rsync://cdimage.ubuntu.com/cdimage/xubuntu/daily-live/20150205/vivid-desktop-i386.iso vivid-desktop-i386.iso

In this example the local 32 bit image file is being synced with xubuntu/daily-live/20150205/vivid-desktop-i386.iso.

Once the sync has taken place you will see the result of the sync echoed in the terminal

vivid-desktop-i386.iso
        961.00M 100%    9.88MB/s    0:01:37 (xfr#1, to-chk=0/1)

zsync

zsync runs from the command you find in the relevant download page on the tracker with no further input

zsync http://cdimage.ubuntu.com/xubuntu/daily-live/20150205/vivid-desktop-amd64.iso.zsync

During the sync process, information is echoed to the terminal. First information about the state of the local image against the image found on the server

Read vivid-desktop-amd64.iso. Target 78.6% complete.

Then during download a running total of speed of download and current progress

downloading from http://cdimage.ubuntu.com/xubuntu/daily-live/20150205/vivid-desktop-amd64.iso:
#################### 100.0% 4059.4 kBps DONE

Finally, once finished you will be shown whether the checksum matches following verification and how much data was fetched from the server

verifying download...checksum matches OK
used 787906560 local, fetched 215340595

If you run the command in a folder which does not contain an existing image to sync with, you will with zsync be warned and can abort the sync with Ctrl+C before too much data is downloaded.

zsync http://cdimage.ubuntu.com/xubuntu/daily-live/20150205/vivid-desktop-amd64.iso.zsync
#################### 100.0% 1036.3 kBps DONE     

No relevent local data found - I will be downloading the whole file. If that's not what you want, CTRL-C out. You should specify the local file is the old version of the file to download with -i (you might have to decompress it with gzip -d first). Or perhaps you just have no data that helps download the file
downloading from http://cdimage.ubuntu.com/xubuntu/daily-live/20150205/vivid-desktop-amd64.iso:
-------------------- 0.1% 993.6 kBps 16:50 ETA  ^C