USE Flags

[pacde]

I want to spark a philosophical debate here and see the pros and cons of the following and adding what you do:

1) in the make.conf file you set your use flags before everything is compiled - my understanding is this will give you what you need (assuming you know beforehand what you need) but it will probably bloat your system because even if you need it all, you probably dont need it everywhere its applicable. Also has the problem of compiling something new without a previous use flag - ie where the previous assumption fails.

2) putting the top 5 or six flags in make.conf but after that use seperate flags for each compile. Here the issue is that previously compiled dependencies may not be compiled with one or more of your use flags (is this an issue? Im not sure).

[Drysh]

My experience:
I had just instaled a gentoo using reiser4, but I decided to go back to reiserfs. I copied the output of "emerge --info" and added that to the make.conf, at stage 1 of the new instalation. Result: I could not emerge the system.
I tried again, installed everything with only a few flags, and then (when the system was ready), I copied the same use flags I was using in the previous attempt to the make.conf, and "emerge -Dev world". Result: everything worked fine.
I think you should not try to change too many use flags when installing the system. I like the approach of changing one (or a few) at a time, and "emerge -Dv --newuse world" after each change. You may end up compiling some programs a lot of times, but when something breaks you know what has gone wrong.
I think that using different use flags for different programs may add a level of complexity to your system that may let it almost impossible to manage. I'm trying to avoid it.

[agent_jdh]

You know you can set per-package (i.e. non-global) USE flags in /etc/portage/package.use (man portage shows you how).

AFAIK this is the preferred method - you have USE flags you know you want to be global in /etc/make.conf, then micro-manage the USE flags for each individual ebuild in /etc/portage/package.use

As for the second part, I'm maybe not 100% sure of what you mean, but I assume you're talking about how packages you have already emerged are affected by USE flag changes. You can run e.g. emerge -upDNv world which will show you what packages are affected by USE flag changes you've made. It's that pesky man portage again.

Also look into revdep-rebuild (part of gentoolkit).
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