[gentoo-dev] Re: Guidelines for IUSE defaults

[Duncan]

Michael Orlitzky posted on Thu, 02 Feb 2017 10:49:41 -0500 as excerpted:

> On 02/02/2017 09:56 AM, Ian Stakenvicius wrote:
>>
>>> On Feb 2, 2017, at 9:11 AM, Michael Orlitzky <mjo@g.o>
>>> wrote:
>>>
>>> IUSE defaults are used in a few different ways:
>>>
>>> 1 To ensure that critical functionality is enabled.
>>>
>>> * Example: force the "unix" module for apache.
>>>
>>>
>> This is not what IUSE defaults are for, this should be done with
>> package.use{,.stable}.{mask,force} in profiles.  If functionality is
>> critical then there (A) shouldn't be a use flag, or (B) shouldn't be a
>> way for USE= in make.conf to disable it.
>>
>>
> If we adopted this policy, then USE="-*" would no longer be guaranteed
> to break the system. It does still ignore your profile defaults, though,
> which presumably are important (e.g. for hardened). So we're still left
> with no way for me to turn off everyone's pet USE flags and keep my
> system working.

If USE="-*" is a guarantee of a broken system, it's a pretty weak one.  
In fact, so is flying with an empty @system (everything in the profile 
negated), as I do both of the above.

And in fact, my gentoo-based-admin life has been far simpler since I set 
it up that way.  =:^)

The biggest benefit of USE="-*" is that I no longer have to worry about 
investigating the "why" of USE flag changes when I change to a different 
profile, or when devs change my existing profile out from under me.  I 
have a set of USE flags I've decided I want (or need for long-term-
installed stuff like kde), and all packages that don't work with that 
default -- for instance, packages that required-use qt4 XOR qt5, already 
have their package.use setup as appropriate.

Otherwise, when I upgrade to a new profile, as I've needed to do several 
times over the nearing a decade and a half I've been running the same 
original installation rolling-update gentoo on rolling-update hardware, I 
have to do a bunch of research on all the USE flags that changed and how 
they affect my existing installation due to --newuse.  This way, that was 
all managed at the time I encountered the original USE flag conflict, and 
the profile I choose doesn't mess with my USE flags at all except via 
forces (which I can override if I have to, but I haven't had to, a 
testament to the wisely conservative usage of forced-USE).

Of course, I can and do still use the USE flags set in a profile as a 
guide, and that was a tremendous help in the kde-apps5/frameworks5/plasma5 
upgrade process despite the fact that I couldn't actually use the profile 
designed for that.

The biggest weakness, meanwhile, is that with USE="-*" there's no easy 
way to actually see what a package's USE-defaults are, without actually 
opening up the ebuild (or at least grepping) to see.  I've often wished 
there was some way to denote the default-on flags in emerge --pretend/--
ask so I could see what they are on a new package, and investigate why if 
necessary, but I understand the problem of a limited available symbol-
space, and actually looking in the ebuild isn't /horribly/ hard... as 
long as there's multiple terminals available to do it in, without 
unnecessarily canceling the --ask output that took so long to appear.

Of course it would be a bit different if I could actually use a profile 
with all the bits I needed, nomultilib, systemd, plasma, amd64, 
primarily.  But until mixins, nomultilib generally means at least some of 
the other stuff isn't available in a profile, so I gotta simply pick the 
nomultilib profile that best matches and check the other profiles, for 
example plasma, using them as a guide to set my flags the way I need them.

Similarly with @system.  Negating the entire thing a package at a time 
and seeing what --depclean wants to clean, then adding as appropriate to 
a set listed in world_sets if it's /really/ needed, means I don't have to 
worry about package.providing openrc, for instance, because it's not 
necessary with systemd, once a single symlink is setup.  Similarly with 
ssh if it's only a stand-alone system you're admining.  And most of the 
@system virtuals can simply be dropped, as specific selections from those 
virtuals have already been added to some set listed in world_sets.

Of course it helps that my routine-use emerge aliases have --ask 
--verbose --oneshot.  (I don't configure those as emerge-defaults because 
I do for example want --pretend occasionally instead of --ask.)  But 
that's a lesson most gentooers should have learned within six months.

Anyway, USE="-*" hardly breaks the system here.  In fact, rather the 
opposite, it fixes what was previously a major headache of a workaround 
for a broken system every time my profile changed, because I was setting 
most USE flags I wanted but until then, not *ALL* of them, in part 
because I couldn't see what I had missed because the profile was setting 
it for me... until it didn't, thus creating the problem.

So for some people, especially those likely to have systems they're 
managing over a profile upgrade, USE="-*" is a guaranteed fix, not a 
guaranteed break. =:^)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman