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Old 11-04-2012, 11:20 AM   #1
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Emerge options and optional dependencies

I am generally a Slackware user so I'm used to more or less manually building and installing packages with slackbuild scripts or just using a few trusted repos for some packages like VLC or ffmpeg. I decided to try Gentoo on a new machine to see how it compares and so far it is amazingly fast, but I'm a little confused about emerge. I have built the base system and I have KDE working, and I have sound, but I have rebuilt somepackages 4 and 5 times due to lacking dependencies. A few packages like VLC and ffmpeg have a lot of optional dependencies. I was wondering if there was a command that would just bring these dependencies in and build them. I think
emerge -D ffmpeg
might accomplish this, but I'm not sure. Do I have this correct?
Old 11-05-2012, 06:02 AM   #2
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Generally you fine tune those optional dependencies with the use flags. There is a USE var in /etc/(portage/)make.conf which is for global flags, and you can set per packase flags in /etc/portage/package.use . That said, it is good, especially when you update world, to add -N (--newuse) option to emerge which will check for changes in use flags and re-emerge/update the packages affected. A typical update command is (if you haven't already read it elsewhere)
emerge -uDNv world
Hope this helps a bit.
Old 11-06-2012, 04:11 PM   #3
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A simple "emerge <package>" will pull all the dependencies of a given package.

If you think that some dependencies are not being pulled correctly then the fact is that that package is not a dependency. And if something that you think should be a dependency is not, then the big chance is that, more than probably, an USE flag in <package> needs to be changed. But it could also be an USE in a dependency, and not directly in <package>.

If you need to go picking random packages by hand, then you are doing something wrong, and you probably should be rather looking at the output of

emerge -pv vlc
and see what's enabled and what isn't.
Old 11-20-2012, 11:50 PM   #4
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Yep, emerge <package> will pull in all dependencies you need based on your USE flags. To check if you're missing dependencies you can optionally run revdep-rebuild.

Last edited by vik; 11-20-2012 at 11:52 PM.
Old 12-06-2012, 05:26 AM   #5
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revdep-rebuild is not meant to be a dep-checker of any kind, though it obviously does some basic dep checking before doing its real work just to make sure that something trivial is not missing.

The real revdep-rebuild taks is to check if the ABI is consistent across all your packages and libraries, so that if some random package was built against any-random-lib-1.x, but you upgraded to any-random-lib-2.x, it will continue to work (by recompiling it against the new library).

Dependencies do not work that way, they are in fact checked *before* you emerge the package, much before you have the binary file that's all revdep-rebuild cares about.


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