Selecting USE flags

[rsambuca]

Does anyone here know of a site for good descriptions for the USE flags? I am starting a gentoo installation, and am at the stage where I am supposed to set the USE flags before compiling the kernel (I am doing the installation via chroot from ubuntu).

I understand why the USE flags are there and how this enables you to configure your system to your own specs and uses, but I can't find any good descriptions of what the flags do. I have found a ton of sites that provide the standard description of the flag, but they do not give enough info to tell me if I need it for something. I have spent a few hours googling the first bunch of flags to figure it out, but there are hundreds of possible flags and at this rate, I won't finish this century.

I obviously could just go with the default desktop config, but isn't that kinda defeating the purpose of this excellent tool?

For example, from the Gentoo Linux Use Variable Descriptions:

acl - Adds support for Access Control Lists.

fine, but now I have to find out what an Access Control List is, etc.

Another question. If I think I have them set up the way I want and set up my rig, will I have to start from scratch and re-compile everything if I later find out I missed a crucial flag?

[termite]

Good luck. USE flag documentation is absurdly lacking. Read http://forums.gentoo.org/viewtopic-p-4183042.html

You could start from the Desktop profile and slim down, but it'll take lots of recompiling. The default profile isn't bad, but you need to add all the desktop stuff you need (X, qt3, qt4, gnome, etc). If you don't want both KDE and gnome, you can do without the respective flags (qt3/4=KDE).

[termite]

If you miss out some flags, you can add them later and recompile. It won't recompile everything, just the packages that use that flag, plus any new ones your new flags pull in.

[rsambuca]

Thanks termite.

I think what I will probably end up doing is start from the desktop default profile, and then trim down stuff from there, or add what I need. For instance, I am pretty much a gnome guy, so I will "-kde". Do I still have to -qt* as well? Also, if I do this and I still want to use a specific qt application like skype or amarok, do I have to change these flags back before compiling these, or does the fact that they are qt specific mean that they will be compiled correctly regardless of the flags?

[termite]

flags are independent of each other. You will need to do -qt3 -qt4 if you don't want any qt.

If you want any qt apps, you can just emerge them and it will pull in what it needs, regardless of your flags. What flags do is enable optional (though sometimes near-essential) options in programs. They really just pass on options to ./configure so you don't have to mess with that.

[Bachstelze]

If you ant to re-emarge only the packages whose flags have changed :

sudo emerge -avDN world

To change your USE flags, you can use either the USE variable in make.conf or define them on a per-package basis in /etc/portage/package.use.

Tip : always do emerge -av package instead of just emerge package, it will show all the USE flags for that package and ask if you really want to emerge it. That way, if you find something wrong with the USE flags, you can correct it before emerging the package.

[termite]

Anytime I use emerge for anything but emerging a specific package, I always do

emerge -avutND world

[Bachstelze]

Same here, though without the "t" unless I really need to track dependencies.

[rsambuca]

Thanks everyone, you are providing me with lots of good input.

One more question: What is the difference between having "-useflag" or not having the "useflag" option listed at all? ie, is "-kde -qt3 -qt4 -arts" much different than just leaving them out entirely?

I guess what I am trying to say is, why are the minus signs necessary if you have to first put the option into the config file in the first place? If I want "gnome" entered, I put it as an option in the USE flags. If I don't want gnome, can't I just leave it out of the config, or do I have to enter -gnome?

I don't think this is coming out very clearly! but I hope you catch my drift.

[termite]

If you're using a profile, some USE flags are set in the profile. You then have to do -myuseflag in your /etc/make.conf to override it. If a flag isn't in your profile, you put myuseflag in /etc/make.conf to enable it.

So, for example, if you're using the 2007.0 desktop profile, it you have to put -gnome in your /etc/make.conf to get rid of the gnome USE flag. However, the 2007.0 desktop profile doesn't have the hardened USE flag, so if you wanted it enabled you'd have to add hardened to your make.conf.

Short answer: for each flag that's in your profile that you want to disable, add a -myflag to your make.conf.

I hope that isn't too unclear....