Tells emerge to include installed packages where USE flags have changed since installation. This option also implies the –selective option. Unlike –newuse, the –changed-use option does not trigger reinstallation when flags that the user has not enabled are added or removed.
–getbinpkg [ y | n ], -g:
Using the server and location defined in PORTAGE_BINHOST (see make.conf(5)), portage will download the information from each binary package found and it will use that information to help build the dependency list. This option implies -k. (Use -gK for binary-only merging.)
sudo emerge -avuDN world
sudo emerge -avuDUg world
–changed-use, -U:
–getbinpkg [ y | n ], -g:
Yeah, I used to use -U but I prefer -N personally. I like the system to be consistent with what it would be from a fresh build.