commands

list gcc profiles:

eselect gcc list

change gcc profile:

eselect gcc set 2
source /etc/profile

list gentoo use flag profile:

eselect profile list

change gentoo use flag profile:

eselect profile set 46

create gpg keys for binpkgs:

getuto

list packages installed:

emerge app-portage/portage-utils

then

qlist -Iv

list 3rd party ebuild repositories:

eselect repository list

add 3rd party ebuild repository:

eselect repository add src_prepare-overlay git https://gitlab.com/src_prepare/src_prepare-overlay

update 3rd party repository:

emaint sync -r src_prepare-overlay

unmask package

edit /etc/portage/package.unmask:

sys-libs/glibc

edit /etc/portage/package.use/vlc

media-video/vlc lua