USE_ORDER
From Gentoo Wiki
This variable is a colon delimited list of where USE flags are pulled from when building packages. If the USE flag is listed in multiple sources, the first one has highest priority.
| Keyword | USE Source |
|---|---|
| env | From the current environment variables (USE and those listed in USE_EXPAND) |
| pkg | /etc/portage/package.use |
| conf | /etc/portage/make.conf |
| defaults | From make.defaults and package.use in the profile (e.g. /etc/portage/make.profile/package.use) (see man 5 portage). |
| pkginternal | From the ebuild itself |
| repo | From make.defaults and package.use in the repo's profiles/ top directory (e.g. /var/db/repos/gentoo/profiles/package.use) (see man 5 portage). |
| env.d | /etc/env.d |
The default USE ordering is USE_ORDER="env:pkg:conf:defaults:pkginternal:repo:env.d".