[Mageia-discuss] Suggestions for the ISO

andre999 andr55 at laposte.net
Mon Nov 8 04:48:27 CET 2010

Renaud MICHEL a écrit :
> On dimanche 07 novembre 2010 at 22:33, Luca Berra wrote :
>>> you must include all intermediate updates packages to create the delta.
>> you just have to keep track of package 1 and n-1, not all of them
> No, because a roll back of a file can happen on any update. If a file is
> changed in release n-2 and rolled back in n-1, if you only consider packages
> 1 n-1 and n you miss the roll back for the people who updated to n-2 but
> missed the update to n-1.
> So the system that will create the deltas must have access to every update
> published since the release, or at least maintain a list of all the files
> that changed in any update. And not only changes in the files themselves,
> but also to their meta-informations, like ownership and mode, and other rpm-
> related meta-informations like %doc or %config.

You would have to keep the current version of all contained files that 
changed since the release version, even if reverted to the state of the 
release package.
As well, in the spec file, you would have to keep meta info on all the 
files that changed, including the files that were replaced, for each update.
This since some users might go from update -2 to update -5, for example.

If a user were to revert to a previous update, in most cases they would 
require either a full update or the release package + the delta update.  
This of course occurs much less frequently.
Note that if the user installed from ISO, they would likely have the 
release package readily available.

It might be possible to avoid including some meta info, by analysing 
which versions of the contained files are more recent, but because there 
are differing ways of representing versions, this is probably not advisable.

Since the spec file will normally be much smaller than the content to be 
installed, this should not be significant overhead in terms of space.

Note that a full update would include all files of the release, and in 
the spec file, the meta info of the new versions of these files.

If much content is changed, it might be advisable to produce a full update.

- André

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