On 30 Aug 2009, at 18:23, Harry Putnam wrote:
...
"USE=<thing>" is supposed to add *support* for <thing>, not
necessarily *install* something called <thing>. Whatever <thing>
means in the context of a specific ebuild depends on what the ebuild
is for, and different ebuilds with the same USE flag may have
entirely different DEPEND stanzas, depending on how the package is
written and what it needs to build/run.
But wouldn't having the gnome use flag active cause updates to pull in
stuff that may not be necessary for the one or two gnome based tools
$user wants?
The way I tend to perceive USE flags is that they generally "add
compatibility" or add "extra options".
So if you emerge mplayer the "dvd" USE flag adds DVD compatibility &
support to mplayer. At one time I used a wifi driver which had an "X"
USE flag - adding that installed a GUI utility for configuring the
driver, if it was omitted then one would simply edit text files "in
the normal way".
If you add these USE flags and install packages that use them, then,
yes, the USE flag may add dependencies and cause additional packages
to be installed. But simply adding a USE flag won't _on its own_
install additional packages - you have to run emerge before they're
drawn in, and you get to review the dependencies at that time.
You might find that if YOU added "USE=gnome" to your make.conf and
reinstalled world that a whole load of extra gnome packages would be
installed. But probably not as much as installing the whole gnome-base/
gnome. The thing is that people who WANT gnome will probably already
have installed gnome-base/gnome and games-mud/gnome-mud and gnome-
extra/gnome-web-photo and gnome-foo/bar - for them adding the gnome
USE flag and emerging mplayer may not install any additional packages
(because they already have so many gnomish packages installed that the
dependencies are already satisfied) but simply add a simple GUI for
mplayer and an entry in the Gnome start menu.
I hope this clarifies, but I apologise if I'm explaining in a way that
makes sense only to me.
I tend to add USE flags to make.conf for stuff I'm likely to use all
the time - support for tiff and jpeg, for instance. Then I consider
other USE flags on a package-by-package basis (`emerge -pv package`).
I may add -truetype to package.use if it indicates that loads of X11
type dependencies will be installed on my headless server, but
generally I don't worry too much about one or three additional small
packages being installed as dependencies - I like Gentoo because it's
small & lean & fast, but it's generally that way, anyway, and most
packages in the tree add little overhead.
Stroller.
