You can specify packages to install in one of four main ways: an ebuild, a tbz2file, a set, or an atom.
ebuild An ebuild must be, at a minimum, a valid Portage package directory name without a version or category, such as portage or python.
Emerge: Gentoo's way of getting and installing applications. DESCRIPTION emerge is the definitive command-line interface to the Portage system.
It is primarily used for installing packages, and emerge can automatically handle any dependencies that the desired package has.
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system refers to a set of packages deemed necessary for your system to run properly.
EBUILDS, TBZ2S, SETS AND ATOMS emerge primarily installs packages.[See FILES below for more information.] Note that a set is generally used in conjunction with --update.If no action is specified, the action is to merge in the specified packages, satisfying any dependencies that they may have.I suggest you review the gentoo doc's here, expecially the portage section. cheers Yes, unfortunately portage is both the name of the package management system on Gentoo (including emerge, among others) and the name of the list of packages available for installation.When you see the "an update to portage is available" message, it is encouraging you to upgrade your package management software, either through 'emerge --oneshot portage' or through 'emerge -u D world'.I just re-read your post and I think I may have misunderstood your question I think you're what is confusing you (and yeah I can see how it can) ..that while `emerge sync` populates the portage tree (w/ ebuilds) ..`emerge portage` updates the app/structure itself.