How To Select Local and Global USE Flags?

[physeetcosmo]

Hello Gentoo Gurus,

i am a n00b, plain and simple. i've worked with Ubuntu and some of OpenSuse and BackTrack but this whole Portage installation of packages is a new concept for me. Very intrigued!!!! It gives me absolute control which is what i want.

Down to my questions: is there a guide to determine WHAT global and local USE flags are optional and required for any given package that i want to install later on my Gentoo system? i know there is a chapter on USE flags in the Gentoo Manual, which is great, but I am curious about the packages LATER that i may want to install....and if those packages affect my Gentoo installation flags NOW?

Also, i am having trouble determining this from the Gentoo Installation Documentation: after i compile and install Gentoo, is it possible to CHANGE the USE flags, or will i have to recompile the Kernel and xWindow? i am currently on Chp5 and don't want to compile/install if i need to determine my global USE flags that are relative to all the packages i want to install FIRST.

i know these are probably broad-reaching questions, just trying to wrap my brain around what i need to know. Any insight is much appreciated!

Thanks in advance!

-Dustin

[John R. Graham]

USE flags can bet set at any time, so don't sweat it. Also, the different profiles set well-chosen default sets of USE flags; most people will want the "desktop" profile.

In the future, if you run into a case where you need to add a USE flag to get the functionality you need, only those packages that are affected by the change will be rebuilt by Portage. See the emerge documentation on the --newuse and --reinstall=changed-use options.

- John
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[physeetcosmo]

John,

That's perfect, just what i needed. i didn't realize i could "rebuild packages on the fly" like that...awesome! Let me check into that emerge documentation.

i worship you, oh Gentoo god!

-Dustin

[John R. Graham]

Nay, my son: just a fellow worshiper, hoping to lead others to the light. (OMG, I think that makes me an Evangelist. )

Seriously, happy to help.

- John
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[NathanZachary]

Hey Dustin,

The only "problem" with not having your USE flags set properly in the beginning is that you might have to recompile some packages later in order to get the desired new package to function correctly. In essence, a simple change to the USE flags and a standard update (emerge -avuDN world) will take care of it. They may seem confusing at first, but they offer a massive amount of customisation opportunities. If you have questions about any USE flags in particular, please feel free to ask. Also, here's a quick guide, but please note that not every part of it is accurate:

http://www.gentoo.org/dyn/use-index.xml
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[physeetcosmo]

Thanks very much NathanZachary,

i figured that i will have many recompilation cycles during my very first Gentoo build. Heck, i already had to change sources as i began with hardened-sources (i am very security conscious) and was advised against it for my first try. So i had to "emerge gentoo-sources" and relink the /usr/src/linux file to the correct kernel.

This was actually good that i had to redo this as i paid attention to the prompts during the unzip of the gentoo-sources kernel as to WHERE it is actually unzipped (good to know!).

i am developing this on an eeePC 1000, with an external HDD so i don't crash my internal SSD .....for the reason mentioned above. Oh yeah, and developing through VirtualBox on my original Ubuntu install....can't "bring down" my entire box during this development cycle .

Thanks for the link, i will take it with a "grain of salt" and probably run into bugs, but i'll keep asking questions.

Grazie!

-Dustin

[Mike Hunt]

Another handy tool that quickly prints a brief description of USE flags is quse from the app-portage/portage-utils package:

[physeetcosmo]

Thanks Mike,

i will put that in my toolbox.

For all the Gurus:

The tutorial states that if i set too many USE Flags (whether it be globals or locals for a package) that it can have poor effects on my system or on the package?
Are there any USE flags you Gurus suggest i set besides:

USE="gnome gtk -kde -qt3 -qt4"

Again, note that i am using the standard Desktop profile.

Maybe i just need to go with these basic flags for now, while i get used to Gentoo?

Thanks again!

-Dustin B

[Mike Hunt]

What I do is set a desktop profile.
Then when I know that I need to enable/disable a specific USE flag and why I need to do it, then OK.
Otherwise, for best results, I leave things at their default values.

For example: I don't have any use right now for bluetooth support, so I have USE="-bluetooth" in /etc/make.conf.
But I do want bash-completion globally enabled, so I change my USE variable: USE="-bluetooth bash-completion"
Then run emerge -uDNav world and examine the output to see if there is anything else.

It does take a while to "grasp the concept" of USE flags.
Of course you are free to experiment any way you wish.
The important things are having fun, and gaining understanding.

[physeetcosmo]

Mike,

That's exactly the "subjective" opinion i guess i was looking for, thanks!

i will experiment and bash-completion was one of the flags i was looking at...sounds useful-tabbing through commands instead of having to remember each one exactly.

-Dustin B

[NathanZachary]

I don't think there is much merit to the idea that having too many USE flags set can have poor effects on your system or a particular package. Having too many optimisation flags for the compiler or linker may, but that is not related to USE flags. Anyway, as Mike suggested, you should probably use the desktop profile and then look at the output of emerge --info. You will then see the global flags that are set by the profile. You can then add or remove some of them by appropriately configuring the USE variable in /etc/make.conf. If you really get into experimenting with USE flags, you will almost certainly have breakage or lack of support for some desired feature along the way. However, you simply recompile the necessary packages with the changed flags and you will be good to go.
_________________
“Truth, like infinity, is to be forever approached but never reached.” --Jean Ayres (1972)
---avatar cropped from =AimanStudio---

[physeetcosmo]

NathanZachary,

Ok, i may have mis-read the tutorial. It very well could have said that about optimization flags for gcc...yeah, yeah that had to have been it.

i'll put

[djsmiley2k]

Hi!

Welcome to the wonderful world of gentoo, I've been here for as long as I can remember and its wonderful!. Stuff breaks randomly, but generally its your own fault so its not so bad

Some useful tools you might like are the gentoo wiki (www.gentoo-wiki.com) and the gentoo portage website (www.gentoo-portage.com) both run by the same guy.

The wiki is pretty obvious in what it provides - infomaton and instructions on how to do things from other users.

The portage site however lists the infomation which I believe is pulled from the ebuild files themselves. It gives you links to the websites for the tool which your installing, and also shows you what useflags are aviable for that item (and also has a list of most of the useflags in portage too). I generally use the site when I want to find a tool for a specific job (the other day i was searching for "pdf" to see what pdf reading software there is).

[physeetcosmo]

Thanks djsmiley2k!

i know that about Linux in general....that if something breaks it's almost ALWAYS my fault One of the reasons that Linux tends to "weed out" the people with no patience, or those that don't care enough about using a Nix OS....but that's another thread.

i will look at portage's website, that will be useful for package installation.

-Dustin B

[physeetcosmo]

Ok Gurus,

Complete n00b question: can i have multiple lines of USE flags? i am a complete organize-freak and was thinking it would be better to "group" the flags according to whatever system they tweak:

[Oerpi]

You can stretch USE=" " over multiple lines but you can only specify it once.

Or you could become even more of a controll freak and use per package USE flags.

Finally changing your profile does not change anything in make.conf, it changes the default flags used but will still respect everything you set manually

[John R. Graham]

It's just Bash, so can use standard shell scripting techniques. I split mine over multiple lines like so:

[physeetcosmo]

Oh cool, didn't extrapolate that they are just BASH script commands....awesome! Thanks!