se non hai dato emerge sync

puoi usare emerge -k pacchetto se hai settato gia nel make.conf PKGDIR=/mnt/cdrom/packages

--usepkg (-k short option)
Tell emerge to use binary packages (from $PKGDIR) if they are
available, thus possibly avoiding some time-consuming compiles.
This option is useful for CD installs; you can export
PKGDIR=/mnt/cdrom/packages and then use this option to have
emerge "pull" binary packages from the CD in order to satisfy
dependencies.