This patch is reducing the size of the ramdisk image generated by the
ironic-agent element. It does remove extra packages (graphical stuff,
dev stuff, miscs, docs, etc...) and purges directories that are not
needed for a ramdisk (like /boot since it boots using an external
kernel)
Currently it was tested generating a Fedora 22 image and reduced the
size of the final image from 464 MB to 211MB compacted (54% decrease).
I was able to boot a VM with 1.3 GiB of ram instead of the previous 3 GiB
needed.
Change-Id: Id6333ca5d99716ccad75ea1964896acf371fa72a
