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Fix bug #445186 - Link to global and local use flags, thanks to Francesco Turco for reporting and providing the easy fix

1 swift 1.7 <?xml version='1.0' encoding='UTF-8'?>
2     <!DOCTYPE sections SYSTEM "/dtd/book.dtd">
3    
4 swift 1.1 <!-- The content of this document is licensed under the CC-BY-SA license -->
5 neysx 1.39 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
6 swift 1.1
7 swift 1.54 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.53 2013/02/09 08:46:08 swift Exp $ -->
8 swift 1.1
9     <sections>
10 swift 1.22
11 neysx 1.44 <abstract>
12 nightmorph 1.46 USE flags are a very important aspect of Gentoo. In this chapter, you learn to
13     work with USE flags and understand how USE flags interact with your system.
14 neysx 1.44 </abstract>
15    
16 swift 1.54 <version>5</version>
17     <date>2013-07-23</date>
18 swift 1.22
19 swift 1.1 <section>
20 nightmorph 1.46 <title>What are USE flags?</title>
21 swift 1.1 <subsection>
22 nightmorph 1.46 <title>The ideas behind USE flags</title>
23 swift 1.1 <body>
24    
25 swift 1.2 <p>
26     When you are installing Gentoo (or any other distribution, or even operating
27     system for that matter) you make choices depending on the environment you are
28     working with. A setup for a server differs from a setup for a workstation.
29     A gaming workstation differs from a 3D rendering workstation.
30     </p>
31    
32     <p>
33     This is not only true for choosing what packages you want to install, but also
34     what features a certain package should support. If you don't need OpenGL, why
35     would you bother installing OpenGL and build OpenGL support in most of your
36     packages? If you don't want to use KDE, why would you bother compiling packages
37 nightmorph 1.46 with KDE support if those packages work flawlessly without?
38 swift 1.2 </p>
39    
40     <p>
41     To help users in deciding what to install/activate and what not, we wanted the
42 swift 1.10 user to specify his/her environment in an easy way. This forces the user into
43 swift 1.11 deciding what they really want and eases the process for Portage, our package
44 nightmorph 1.40 management system, to make useful decisions.
45 swift 1.2 </p>
46    
47 swift 1.1 </body>
48     </subsection>
49     <subsection>
50 nightmorph 1.46 <title>Definition of a USE flag</title>
51 swift 1.1 <body>
52    
53 swift 1.2 <p>
54 nightmorph 1.46 Enter the USE flags. Such a flag is a keyword that embodies support and
55     dependency-information for a certain concept. If you define a certain USE flag,
56 swift 1.3 Portage will know that you want support for the chosen keyword. Of course
57 swift 1.2 this also alters the dependency information for a package.
58     </p>
59    
60     <p>
61 swift 1.6 Let us take a look at a specific example: the <c>kde</c> keyword. If you do not
62 swift 1.2 have this keyword in your <c>USE</c> variable, all packages that have
63     <e>optional</e> KDE support will be compiled <e>without</e> KDE support. All
64     packages that have an <e>optional</e> KDE dependency will be installed
65     <e>without</e> installing the KDE libraries (as dependency). If you have defined
66     the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
67     support, and the KDE libraries will be installed as dependency.
68     </p>
69    
70     <p>
71     By correctly defining the keywords you will receive a system tailored
72     specifically to your needs.
73     </p>
74    
75 swift 1.1 </body>
76     </subsection>
77     <subsection>
78 nightmorph 1.46 <title>What USE flags exist?</title>
79 swift 1.1 <body>
80    
81 swift 1.2 <p>
82 nightmorph 1.46 There are two types of USE flags: <e>global</e> and <e>local</e> USE flags.
83 swift 1.2 </p>
84    
85     <ul>
86     <li>
87 nightmorph 1.46 A <e>global</e> USE flag is used by several packages, system-wide. This is
88     what most people see as USE flags.
89 swift 1.2 </li>
90     <li>
91 nightmorph 1.46 A <e>local</e> USE flag is used by a single package to make package-specific
92 swift 1.2 decisions.
93     </li>
94     </ul>
95    
96     <p>
97 nightmorph 1.46 A list of available global USE flags can be found <uri
98 swift 1.54 link="/dyn/use-index.xml#doc_chap1">online</uri> or locally in
99 neysx 1.38 <path>/usr/portage/profiles/use.desc</path>.
100 swift 1.2 </p>
101    
102 swift 1.18 <p>
103 swift 1.54 A list of available local USE flags can be found <uri
104     link="/dyn/use-index.xml#doc_chap2">online</uri> or locally in
105 swift 1.18 <path>/usr/portage/profiles/use.local.desc</path>.
106     </p>
107    
108 swift 1.1 </body>
109     </subsection>
110     </section>
111     <section>
112 nightmorph 1.46 <title>Using USE flags</title>
113 swift 1.1 <subsection>
114 nightmorph 1.46 <title>Declare permanent USE flags</title>
115 swift 1.1 <body>
116    
117 swift 1.2 <p>
118 nightmorph 1.46 In the hope you are convinced of the importance of USE flags we will now inform
119     you how to declare USE flags.
120 swift 1.2 </p>
121    
122     <p>
123 nightmorph 1.46 As previously mentioned, all USE flags are declared inside the <c>USE</c>
124     variable. To make it easy for users to search and pick USE flags, we already
125     provide a <e>default</e> USE setting. This setting is a collection of USE flags
126 swift 1.2 we think are commonly used by the Gentoo users. This default setting is declared
127 swift 1.28 in the <path>make.defaults</path> files part of your profile.
128 swift 1.2 </p>
129    
130 swift 1.28 <p>
131     The profile your system listens to is pointed to by the
132 swift 1.52 <path>/etc/portage/make.profile</path> symlink. Each profile works on top of
133     another, larger profile, the end result is therefore the sum of all profiles.
134     The top profile is the <path>base</path> profile
135 swift 1.28 (<path>/usr/portage/profiles/base</path>).
136     </p>
137    
138     <p>
139 swift 1.53 Let us take a look at this default setting for the 13.0 profile:
140 swift 1.28 </p>
141    
142 swift 1.53 <pre caption="Cumulative make.defaults USE variable for the 13.0 profile">
143 nightmorph 1.50 <comment>(This example is the sum of the settings in base, default/linux,
144 swift 1.53 default/linux/x86 and default/linux/x86/13.0/)</comment>
145 nightmorph 1.50 USE="a52 aac acpi alsa branding cairo cdr dbus dts dvd dvdr emboss encode exif
146     fam firefox flac gif gpm gtk hal jpeg lcms ldap libnotify mad mikmod mng mp3
147     mp4 mpeg ogg opengl pango pdf png ppds qt3support qt4 sdl spell
148 nightmorph 1.51 startup-notification svg tiff truetype vorbis unicode usb X xcb x264 xml xv
149     xvid"
150 swift 1.2 </pre>
151    
152     <p>
153     As you can see, this variable already contains quite a lot of keywords. Do
154 swift 1.25 <b>not</b> alter any <path>make.defaults</path> file to tailor
155 swift 1.2 the <c>USE</c> variable to your needs: changes in this file will be undone when
156     you update Portage!
157     </p>
158    
159     <p>
160     To change this default setting, you need to add or remove keywords to the
161     <c>USE</c> variable. This is done globally by defining the <c>USE</c> variable
162 swift 1.52 in <path>/etc/portage/make.conf</path>. In this variable you add the extra USE
163     flags you require, or remove the USE flags you don't want. This latter is done
164     by prefixing the keyword with the minus-sign ("-").
165 swift 1.2 </p>
166    
167     <p>
168     For instance, to remove support for KDE and QT but add support for ldap, the
169 swift 1.52 following <c>USE</c> can be defined in <path>/etc/portage/make.conf</path>:
170 swift 1.2 </p>
171    
172 swift 1.52 <pre caption="An example USE setting in /etc/portage/make.conf">
173 nightmorph 1.50 USE="-kde -qt4 ldap"
174 swift 1.2 </pre>
175    
176 swift 1.19 </body>
177     </subsection>
178     <subsection>
179     <title>Declaring USE flags for individual packages</title>
180     <body>
181    
182 swift 1.17 <p>
183     Sometimes you want to declare a certain USE flag for one (or a couple) of
184     applications but not system-wide. To accomplish this, you will need to create
185     the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
186 nightmorph 1.49 <path>/etc/portage/package.use</path>. This is usually a single file, but can
187     also be a directory; see <c>man portage</c> for more information. The following
188     examples assume <path>package.use</path> is a single file.
189 swift 1.17 </p>
190    
191     <p>
192     For instance, if you don't want <c>berkdb</c> support globally but you do want
193     it for <c>mysql</c>, you would add:
194     </p>
195    
196     <pre caption="/etc/portage/package.use example">
197     dev-db/mysql berkdb
198     </pre>
199    
200     <p>
201     You can of course also explicitly <e>disable</e> USE flags for a certain
202     application. For instance, if you don't want <c>java</c> support in PHP:
203     </p>
204    
205     <pre caption="/etc/portage/package.use 2nd example">
206     dev-php/php -java
207     </pre>
208    
209 swift 1.1 </body>
210     </subsection>
211     <subsection>
212 nightmorph 1.46 <title>Declare temporary USE flags</title>
213 swift 1.1 <body>
214    
215 swift 1.2 <p>
216 nightmorph 1.46 Sometimes you want to set a certain USE setting only once. Instead of editing
217 swift 1.52 <path>/etc/portage/make.conf</path> twice (to do and undo the USE changes) you
218     can just declare the USE variable as environment variable. Remember that, when
219     you re-emerge or update this application (either explicitly or as part of a
220     system update) your changes will be lost!
221 swift 1.2 </p>
222    
223     <p>
224 nightmorph 1.46 As an example we will temporarily remove java from the USE setting
225 nightmorph 1.45 during the installation of seamonkey.
226 swift 1.2 </p>
227    
228 swift 1.13 <pre caption="Using USE as environment variable">
229 nightmorph 1.45 # <i>USE="-java" emerge seamonkey</i>
230 swift 1.2 </pre>
231    
232 swift 1.1 </body>
233     </subsection>
234     <subsection>
235 swift 1.15 <title>Precedence</title>
236 swift 1.2 <body>
237    
238     <p>
239 neysx 1.16 Of course there is a certain precedence on what setting has priority over the
240 swift 1.32 USE setting. You don't want to declare <c>USE="-java"</c> only to see that
241     <c>java</c> is still used due to a setting that has a higher priority.
242     The precedence for the USE setting is, ordered
243 swift 1.2 by priority (first has lowest priority):
244     </p>
245    
246     <ol>
247     <li>
248 swift 1.25 Default USE setting declared in the <path>make.defaults</path> files part of
249     your profile
250 swift 1.2 </li>
251     <li>
252 swift 1.52 User-defined USE setting in <path>/etc/portage/make.conf</path>
253 swift 1.2 </li>
254     <li>
255 swift 1.17 User-defined USE setting in <path>/etc/portage/package.use</path>
256     </li>
257     <li>
258 swift 1.2 User-defined USE setting as environment variable
259     </li>
260     </ol>
261 swift 1.4
262     <p>
263 cam 1.27 To view the final <c>USE</c> setting as seen by Portage, run <c>emerge
264     --info</c>. This will list all relevant variables (including the <c>USE</c>
265     variable) with the content used by Portage.
266 swift 1.4 </p>
267    
268 cam 1.27 <pre caption="Running emerge --info">
269     # <i>emerge --info</i>
270 swift 1.4 </pre>
271 swift 1.2
272 swift 1.1 </body>
273     </subsection>
274 swift 1.12 <subsection>
275     <title>Adapting your Entire System to New USE Flags</title>
276     <body>
277    
278     <p>
279     If you have altered your USE flags and you wish to update your entire system to
280 swift 1.21 use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
281 swift 1.12 </p>
282    
283     <pre caption="Rebuilding your entire system">
284 swift 1.21 # <i>emerge --update --deep --newuse world</i>
285 swift 1.12 </pre>
286    
287     <p>
288 swift 1.20 Next, run Portage's depclean to remove the conditional dependencies that
289 swift 1.12 were emerged on your "old" system but that have been obsoleted by the new USE
290     flags.
291     </p>
292    
293     <warn>
294 cam 1.27 Running <c>emerge --depclean</c> is a dangerous operation and should be handled
295 swift 1.12 with care. Double-check the provided list of "obsoleted" packages to make sure
296     it doesn't remove packages you need. In the following example we add the
297     <c>-p</c> switch to have depclean only list the packages without removing them.
298     </warn>
299    
300     <pre caption="Removing obsoleted packages">
301 cam 1.27 # <i>emerge -p --depclean</i>
302 swift 1.12 </pre>
303    
304     <p>
305 swift 1.21 When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
306     applications that are dynamically linked against shared objects provided by
307     possibly removed packages. <c>revdep-rebuild</c> is part of the
308     <c>gentoolkit</c> package; don't forget to emerge it first.
309     </p>
310    
311     <pre caption="Running revdep-rebuild">
312     # <i>revdep-rebuild</i>
313     </pre>
314    
315     <p>
316     When all this is accomplished, your system is using the new USE flag settings.
317 swift 1.12 </p>
318    
319     </body>
320     </subsection>
321 swift 1.1 </section>
322     <section>
323 nightmorph 1.46 <title>Package specific USE flags</title>
324 swift 1.1 <subsection>
325 nightmorph 1.46 <title>Viewing available USE flags</title>
326 swift 1.1 <body>
327 swift 1.2
328     <p>
329 nightmorph 1.46 Let us take the example of <c>seamonkey</c>: what USE flags does it listen to? To
330 swift 1.21 find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
331     options:
332 swift 1.2 </p>
333    
334 nightmorph 1.46 <pre caption="Viewing the used USE flags">
335 nightmorph 1.45 # <i>emerge --pretend --verbose seamonkey</i>
336 swift 1.2 These are the packages that I would merge, in order:
337    
338     Calculating dependencies ...done!
339 nightmorph 1.45 [ebuild R ] www-client/seamonkey-1.0.7 USE="crypt gnome java -debug -ipv6
340     -ldap -mozcalendar -mozdevelop -moznocompose -moznoirc -moznomail -moznopango
341     -moznoroaming -postgres -xinerama -xprint" 0 kB
342 swift 1.2 </pre>
343    
344     <p>
345     <c>emerge</c> isn't the only tool for this job. In fact, we have a tool
346 swift 1.30 dedicated to package information called <c>equery</c> which resides in the
347 swift 1.2 <c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
348     </p>
349    
350     <pre caption="Installing gentoolkit">
351 swift 1.21 # <i>emerge gentoolkit</i>
352 swift 1.2 </pre>
353    
354     <p>
355 nightmorph 1.46 Now run <c>equery</c> with the <c>uses</c> argument to view the USE flags of a
356 swift 1.2 certain package. For instance, for the <c>gnumeric</c> package:
357     </p>
358    
359 nightmorph 1.46 <pre caption="Using equery to view used USE flags">
360 neysx 1.48 # <i>equery --nocolor uses =gnumeric-1.6.3 -a</i>
361 rane 1.42 [ Searching for packages matching =gnumeric-1.6.3... ]
362 neysx 1.48 [ Colour Code : set unset ]
363     [ Legend : Left column (U) - USE flags from make.conf ]
364     [ : Right column (I) - USE flags packages was installed with ]
365 rane 1.42 [ Found these USE variables for app-office/gnumeric-1.6.3 ]
366     U I
367 neysx 1.48 - - debug : Enable extra debug codepaths, like asserts and extra output.
368     If you want to get meaningful backtraces see
369     http://www.gentoo.org/proj/en/qa/backtraces.xml .
370     + + gnome : Adds GNOME support
371     + + python : Adds support/bindings for the Python language
372     - - static : !!do not set this during bootstrap!! Causes binaries to be
373     statically linked instead of dynamically
374 swift 1.2 </pre>
375 swift 1.1
376     </body>
377     </subsection>
378     </section>
379     </sections>

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