website/content/blog/downloadchanges.md

title	date	draft	tags	medium_enabled
Download Changes	2020-04-12T15:28:31-04:00	false		true

When testing daily ISO images, it is useful to only download the parts of the ISO that has changed since the previous days. That way we can preserve time and bandwidth.

Rsync method

This approach requires server-side support, and a lot of flags specified.

rsync --times \
  --compress --partial \
  --progress --stats \
  --human-readable \
  --human-readable \
  rsync://cdimage.ubuntu.com/cdimage/kubuntu/daily-live/20200412/focal-desktop-amd64.iso \
  kubuntu-focal-desktop-amd64.iso

Flag	Description
--times	Transfer modification times along with the files.
--compress	Compress the file data during transit.
--partial	Keep partial downloads if interrupted.
--progress	Print information showing the progress of the /transfer.
--stats	Print a set of statistics on the file transfer.
--human-readable	Output numbers in a more human readable format, can use up to 3 times.

Zsync method

This approach does not involve adding a bunch of flags, but it does require the provider to have a .zsync file on their server and for the user to have the zync package installed. This package typically isn't installed by default on most systems.

zsync http://cdimage.ubuntu.com/kubuntu/daily-live/20200412/focal-desktop-amd64.iso.zsync