6.4. Delta RPM Packages

Delta RPM packages contain the difference between an old and a new version of an RPM package. Applying a delta RPM on an old RPM results in the complete new RPM. It is not necessary to have a copy of the old RPM, because a delta RPM can also work with an installed RPM. The delta RPM packages are even smaller in size than patch RPMs, which is an advantage when transferring update packages over the Internet. The drawback is that update operations with delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs.

The prepdeltarpm, writedeltarpm, and applydeltarpm binaries are part of the delta RPM suite (package deltarpm) and help you create and apply delta RPM packages. With the following commands, create a delta RPM called new.delta.rpm. The following command assumes that old.rpm and new.rpm are present:

prepdeltarpm -s seq -i info old.rpm > old.cpio
prepdeltarpm -f new.rpm > new.cpio
xdelta delta -0 old.cpio new.cpio delta
writedeltarpm new.rpm delta info new.delta.rpm

Finally, remove the temporary working files old.cpio, new.cpio, and delta.

Using applydeltarpm, you can reconstruct the new RPM from the file system if the old package is already installed:

applydeltarpm new.delta.rpm new.rpm

To derive it from the old RPM without accessing the file system, use the -r option:

applydeltarpm -r old.rpm new.delta.rpm new.rpm
  

See /usr/share/doc/packages/deltarpm/README" for technical details.