Thanks for the reply. The points raised are important and must be validated, before we implement such a system. I will now try to debunk the FUD ;)
basically, drpm does construct a byte-for-byte rpm that is equivalent to the new rpm, then it installs that. If constructing such rpm fails for whatever reason, the drpm operation is aborted, and the system falls back to full rpms. One more interesting point to note, is that checking whether constructing a new rpm will be successful, is done prior to downloading the drpm, so bandwidth usage is kept minimal.
While researching the topic, I found the mandriva folks were having similar discussions.
Comment #13 is from the deltarpm author
I also stumbled upon a forum poll, about adding deltarpm support for 2007 in Mandriva
Surprisingly most users do think it's nice feature to have. Although not too many people voted, but that's what we have.
BTW, using bittorrent does not seem like a good idea for yum: http://wiki.linux.duke.edu/YumTodont
On Jan 13, 2007, at 5:11 PM, Ahmed Kamal wrote:
> We should be able to sign the drpms (not sure yet!) Reconstructing
> the new rpm from ondisk files, doesn't look bad security wise,
> because the new data is signed. If the on disk files are not
> trusted, this means the system is already compromised!
Installed files get modified for reasons other than a hacked system.
Think about config files that the sysadmin edits after a package is
installed. Think about documentation files, whose may not be
installed at all. Think about dealing with file conflicts between
installed packages. Run 'rpm -Va' on a sample of Fedora systems and
tell me that all those changes just don't matter... And make sure to
talk to a sysadmin who has had to recover from a rootkit-ed system,
and tell them that the rootkit'd files will get rolled into their
newly installed packages if drpm is enabled during recovery.
Relying on the integrity of installed files when generating and
applying rpm diffs is just a bad idea, period. It's a hack that
relies on hope instead of best practices, and it gives up the
guarantees that are a substantial part of rpm's value. Any rpm delta
solution must produce results that are identical to the original
desired file, down to the last byte.
Maybe there is a clever way to use a network server and local
installed files, along with the rsync algorithm, to generate a .rpm
file that is guaranteed to be byte-for-byte identical to the desired
file. Mix BitTorrent technology in there, and there is plenty of room
for innovation without resorting to a really bad hack. :)
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