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Why do we not configure USE flags before updating the world?
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Chrjs
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Joined: 27 Aug 2019
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PostPosted: Wed Oct 09, 2019 6:23 pm    Post subject: Why do we not configure USE flags before updating the world? Reply with quote

In the handbook; if you follow along the steps, you are asked to select a profile, and then update the world set using
Code:
emerge --ask --verbose --update --deep --newuse @world

Afterwards comes the section about configuring the USE variable in /etc/portage/make.conf

Shouldn't I configure USE flags before emerging? What if a profile contains a global USE flag that causes a package to be pulled that I don't want? An example came to mind such as the "crypt" USE flag for kde-plasma/plasma-meta which will cause kde-plasma/plasma-vault to be automatically pulled in by emerge, which I don't want. But kde-plasma/plasma-meta probably isn't pulled by the desktop/plasma profile itself, so I think my example is dumb.

Also, what exactly does the desktop/plasma profile do? Does it only apply a bunch of USE flags meant to make it easier to install KDE plasma?

Sorry, am very new to Gentoo and Linux in general.
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NeddySeagoon
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Joined: 05 Jul 2003
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PostPosted: Wed Oct 09, 2019 7:12 pm    Post subject: Reply with quote

Chrjs,

A profile in Gentoo is a set of presets, mostly USE flags to simplify configuring a system for your intended purpose on your selected architecture.

Its mostly preset USE flags, but there are things like package.mask that stops you installing some things altogether.
Reasons are given in comments in the file.

Gentoo has a hierarchy of things like this. There are ways lower down the hierarchy to change things set further up.

If your selected profile contains USE=foo and you don't want USE=foo you can set USE=-foo in make.conf
That turns off USE=foo for your entire install.
Alternatively, you cat change your profile to one that does not have USE=foo in the first place. That might also have USE=-bar and you want USE=bar.
In short, make.conf lets you fine tune your global settings provided by your profile.
There is no single correct way to do that.

At the next level down, anything in make.conf can be set in other files (not provided) in /etc/portage on a per package basis. This allows you to set USE=foo or USE=-foo on individual packages.
This far, portage remembers what you did.

For completeness,
Code:
USE=foo emerge ... 
does what you expect but portage will not remember it.
Its useful for breaking circular dependencies where you only need a temporary USE change.

Yes, you can configure USE flags before you run
Code:
emerge --ask --verbose --update --deep --newuse @world

It may or may not save compile time.
Anything you install that you don't need will be removed as part of normal system maintenance.

To see what a profile does, select one then run
Code:
emerge --info

Select another and run the command again

To see the changes on your install, run
Code:
emerge -epv @world

All the changed USE flags will be in green with an * beside them.

None of these commands actually change your install any, so its safe to look.

Don't be sorry for being at the start of the learning curve. We all remember it.
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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saboya
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PostPosted: Wed Oct 09, 2019 8:31 pm    Post subject: Reply with quote

I think it's meant to get you up and running before start messing around with USE flags, which could take a while if you want to carefully analyze what you want in your system, especially for those not familiar with Gentoo.

Welcome to Gentoo :)
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sitquietly
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Joined: 23 Oct 2010
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PostPosted: Wed Oct 09, 2019 8:50 pm    Post subject: Reply with quote

saboya wrote:
I think it's meant to get you up and running before start messing around with USE flags, which could take a while if you want to carefully analyze what you want in your system...


I've done it "against the advice of the handbook" and made a mess that is hard to clean up. Think of a profile as a tested linux distro. e.g. the plasma profile gives you a linux plasma system that is known to work. If you start fine-tuning your own prejudices before fully emerging that "distro" you may make it not work. Your fine-tuned variation may not even emerge. The safe route recommended by the handbook is to (1) First, Trust Us! tell us what kind of system you want and then emerge it the way we know it works and satisfies most people, and (2) then make some incremental change in USE settings, remove some packages. The soonest you get to a fully emerged system the better. It's so much easier to work with a system in that clean state!

The alternative for those willing to take the responsibility of configuring a lot more choices on their own is to choose a more general profile (e.g. 17.1/no-multilib or 17.1/desktop) -- get it fully emerged! -- and then add features (USE) and constraints (mask) to that to create their own hybrid system.

So, no you shouldn't configure USE flags before first completing the emerge of your profile.
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Chrjs
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PostPosted: Thu Oct 10, 2019 12:53 pm    Post subject: Reply with quote

Very good answers. Thank you all.
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