The ekeyword tool should be used to manipulate the KEYWORDS variable. Using this tool will guarantee that you get the correct keyword ordering manual editing may screw this up. The usage is ekeyword changes ebuilds. Valid changes are in the form sparc (to mark stable), ~sparc (to mark unstable), -sparc (to mark unavailable) and ^sparc (to remove the sparc keyword). The special all keyword is useful when doing version bumps ekeyword ~all foo-1.23.ebuild will drop all currently present keywords to unstable. See ekeyword(1) for details.