DeltaISOs

[Jonathan Dieter]

On Sun, 2010-08-29 at 14:29 -0400, David wrote:
> I think that I understand the principal behind this. Disk space nor
> bandwidth are not problems for me. I was thinking of others that might
> have a bandwidth/byte counter problem.
> 
> Explain to me just how downloading only a part of the new ISO, the
> changes, and then creating the new one with parts of the old ISO and the
> new parts. How can that be the same as downloading the whole new ISO?
> 
> Or am I not understanding how this works.

The steps in a deltaiso lifecycle are as follows:

The Fedora project (or an interested user) creates the deltaiso.  To do
so, they need the old iso and the new iso, and they generate the
deltaiso using makedeltaiso.  So, if we wanted to create a deltaiso from
F14-Alpha to F14-Beta, we might do something like:

makedeltaiso F14-Alpha.iso F14-Beta.iso F14-Alpha_Beta.diso

This deltaiso will contain the *difference* from F14-Alpha to F14-Beta.


A user who has the iso for F14-Alpha (and low bandwidth) will then
download F14-Alpha_Beta.diso and run something like:

applydeltaiso F14-Alpha.iso F14-Alpha_Beta.diso F14-Beta.iso

They will then "magically" get F14-Beta.iso without having to download
it.  Of course, applying the deltaiso will take a long time, so it
really only makes sense to use it if you're on a limited bandwidth
connection.

Please note that normal users should never need to *make* the deltaiso,
they should just *apply* them.  And Andre's done a great job of making
deltaiso's available, especially during prerelease.

Jonathan
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