Why use "USE Flags"?

I have the most noobish question in the world. I am aiming to setup samba, apache, php, and ssh, on my new gentoo machine. In the future I want compiz-fusion but not right now.

All the tutorials I've read so far say to put USE Flags places. However I installed dhcpcd and apache2 without doing so and they work fine.

Other than removing dependencies on libraries I won't to use with apache2, making performance faster.
why do I need to use "USE Flags"?


*edit*
Basically I don't want to go through the hassle of use flags while I design my media server, will it break anything if I don't set
use flags is what I want to know.

The USE-flags adds or removes functionality. I.E. if you want support for JACK in some packages (those that supports JACK), you'll have to add "jack" to your USE-flags.
It can also be used to make sure you don't get a functionality you don't want. Say you run gnome and don't want all those Qt-packages, you can add "-qt" to you USE-flags to make sure packages don't fetch them.

I see, so this brings up another question.

Right now I'm not concerned about performance. I'm running this on my old main computer. A 3.2ghz, 1gb (2x512) ddr2.
If I don't use the USE Flags, will it just install things with everything enabled?

I've seen a list of the default USE flag entries, list of all use flags on the Gentoo website ... you can see that USE flags are an important aspect of Gentoo here.

I have not used Gentoo much and have only done a couple of installs but I think getting the right combination of USE flags is essential for Gentoo. I have ended up having to change USE flags because I decided I wanted to add features and seemed to be forced down the route of unmerging and reemerging some packages to make the system work again. I'd say its worth going through the list of USE flags and pick the ones you think you need (but don't go mad otherwise that can cause problems as well). Set the correct USE flag combination at the beginning of the install process ;)

The difference between people who love Gentoo and people who don't seems to be people who love it have found the right combination of USE flags :lol:

No you will not.
By emerging with "emerge -av [package]" you will see what useflags are enabled, and you will be asked if you want to proceed or not.

However, I would recommend you to take the go through what useflags you want/need. Also when you use -av you will find new flags now and then. If they sound interesting, check them out and add them to your useflags if they do nice things.

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Originally Posted by BinarySpike

Other than removing dependencies on libraries I won't to use with apache2, making performance faster.
why do I need to use "USE Flags"?

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They enable/disable functionalities (adding/disabling dependencies in the way, which is just a collateral effect). They can be also used to control a number of optional features. Some of them are hardcoded into the profiles, so if you use a given profile it might be impossible to change the default value of a given flag.

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Basically I don't want to go through the hassle of use flags while I design my media server, will it break anything if I don't set
use flags is what I want to know.

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No. The only problem is that if you don't enable a flag that you need, you might need to recompile some packages afterwards. But that's not a critical problem.

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Originally Posted by FireArrow

The USE-flags adds or removes functionality. I.E. if you don't want support for JACK in some packages (those that supports JACK), you'll have to add "jack" to your USE-flags.

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I assume "-jack" instead of "jack", since you are talking about "disabling".

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It can also be used to make sure you don't get a functionality you don't want. Say you run gnome and don't want all those Qt-packages, you can add "-qt" to you USE-flags to make sure packages don't fetch them.

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Not meant to be picky, but just to clarify: USE="-qt" doesn't guarantee you that the qt package is not going to be installed. It just guarantees you that if it's optional for a given program, then it will not be linked against qt. However, if you install a program that needs qt (and that means it's *required* and not *optional*) then qt will be installed anyway. It doesn't matter if you USE="-qt".

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Originally Posted by BinarySpike

Right now I'm not concerned about performance. I'm running this on my old main computer. A 3.2ghz, 1gb (2x512) ddr2.
If I don't use the USE Flags, will it just install things with everything enabled?

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No. Use emerge -av <package> to see the list of current use flags for a given package as someone suggested above. The default use flags vary depending on your profile and architecture.

To sum up: to get the right use flags set for you can take a bit of time, but don't be afraid of that, there's no need to hurry and the worse thing that can happen is that you might need to recompile something to include something that you left out the first time you compiled a given package.

@i92guboj: Thank you for pointing out my error for the first (even if it was the other way around, fixed in my post now), and clarifying the second.
Your post pretty much sums it all up =)

Thanks, i92guboj!

FireArrow is right, that pretty much sums up the USE flags!

If you don't want to bother with USE flags, why use Gentoo in the first place? Why don't use something like Debian which is highly configurable instead?

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Originally Posted by tvilkov

If you don't want to bother with USE flags, why use Gentoo in the first place? Why don't use something like Debian which is highly configurable instead?

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Because it's fun?

But seriously, I've been using Gentoo for only a couple weeks now and it's WAY easier than Debian to begin with (once you actually install it lol)

Basically when I install something I know 3 things
- /etc/<name>/ contains the configure file
- /etc/init.d/<name> is how I start it
- Gentoo Wiki has configuration guide.
(okay so maybe not all the time, but so far for me)

I have sshd, dhcpcd, apache, php, samba, postfix, and dovecot. AND THAT'S ALL. It's not bloated down, exactly what I wanted.