Re: effectiveness of rsync and apt
* Brian Eaton (eaton.lists@gmail.com) [060501 19:21]:
> On 5/1/06, Andreas Barth <aba@not.so.argh.org> wrote:
> >Or you could create the diffdebs before upload or on ftp-master, and
> >include the diffdebs somehow in the Packages file (so they're signed as
> >well by the usual mechanismn).
> My initial view is that any delta package system that doesn't
> reproduce the exact same .debs as downloading the package from scratch
> is a non-starter.
Why that? Of course, you need all the maintainer scripts etc in the
diffdeb, but not all the regular files.
Normally, the operation works as follows:
call maintainer script old-prerm upgrade newversion
call maintainer script new-preinst upgrade oldversion
unpack new packages files, temporarily renaming the old packages file (1)
call maintainer script old-postrm upgrade newversion
remove any files only in the old package (2)
maintainer scripts and file list are being replaced
delete backup files (3)
call maintainer script new-postinst upgrade oldversion
Now, the difference would be: record in the diffdeb package which files
go unchanged, so at (1) only the changed files are overwritten. At (2),
only the files neither in the new package nor in the unchanged list are
removed, and (3) just deletes less backup files. In the end, the only
difference is that less files are written, and no new inode is used by
the script.
Of course, you basically need to adjust the new "normal" deb so that the
files have the same date in the normal deb and in the previous deb (so
you basically need a way to say "create a diffdeb to that deb", and you
get the diffdeb and the adjusted new deb for upload (so it needs to
happen prior to upload).
> It opens up the door to all kinds of funky
> maintenance questions like "well, did you install from the patch
> package, or the real package? was this a bug in the patch package?",
> etc... Ideally, package maintainers will never have a reason to care
> that delta packages exist.
Exactly.
Cheers,
Andi
--
http://home.arcor.de/andreas-barth/
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