On 12/31/2009 06:41 AM, Amit Dor-Shifer wrote:
> In cont. to my prev. question
> (http://archives.gentoo.org/gentoo-portage-dev/msg_9973fd6c12d7c2088457697f49ea2f5e.xml)
> 
> 
> Can I append use.force/package.use.force/package.use or similar to an
> overlay, and by that control USE flags on the host?

With EAPI 1 and greater you can use IUSE="+flag" to enable flags by
default in an ebuild. If you need to modify the profile then this is
a good way to do it:

  http://en.gentoo-wiki.com/wiki/Custom_Profiles#Simple_Profile_Setup

> Though not necessarily related, I'm trying to resolve a broader issue:
> whether it is possible to extend a profile via an overlay.
> 
> I've read http://bugs.gentoo.org/show_bug.cgi?id=133740#c6. Also, I've
> found http://en.gentoo-wiki.com/wiki/Custom_Profiles which states how
> custom profiles can be integrated into a system, yet with the caveat of
> modifying local portage files (removing the symlink to the profile). I'd
> appreciate to know if it's also possible to gain similar results w/o
> touching files on the hosting portage setup.

Other than IUSE defaults, the only way is to create a
/etc/make.profile directory and list multiple profiles in the
"parent" file.

> In a/m bug, the lack of documentation in this area is mentioned . I'm
> wondering if this has changed since those comments were written, as I'm
> confounded by bits and pieces I'm fishing out w/google.

The information in the wiki seems current.
-- 
Thanks,
Zac