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further clarification that package.use can be a single file or a whole directory, bug 196594

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 nightmorph 1.49 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.48 2007/07/04 13:47:19 neysx 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 nightmorph 1.49 <version>1.38</version>
17     <date>2007-10-21</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 1.2 link="/dyn/use-index.xml">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 nightmorph 1.46 A list of available local USE flags can be found locally in
104 swift 1.18 <path>/usr/portage/profiles/use.local.desc</path>.
105     </p>
106    
107 swift 1.1 </body>
108     </subsection>
109     </section>
110     <section>
111 nightmorph 1.46 <title>Using USE flags</title>
112 swift 1.1 <subsection>
113 nightmorph 1.46 <title>Declare permanent USE flags</title>
114 swift 1.1 <body>
115    
116 swift 1.2 <p>
117 nightmorph 1.46 In the hope you are convinced of the importance of USE flags we will now inform
118     you how to declare USE flags.
119 swift 1.2 </p>
120    
121     <p>
122 nightmorph 1.46 As previously mentioned, all USE flags are declared inside the <c>USE</c>
123     variable. To make it easy for users to search and pick USE flags, we already
124     provide a <e>default</e> USE setting. This setting is a collection of USE flags
125 swift 1.2 we think are commonly used by the Gentoo users. This default setting is declared
126 swift 1.28 in the <path>make.defaults</path> files part of your profile.
127 swift 1.2 </p>
128    
129 swift 1.28 <p>
130     The profile your system listens to is pointed to by the
131     <path>/etc/make.profile</path> symlink. Each profile works on top of another,
132     larger profile, the end result is therefore the sum of all profiles. The top
133     profile is the <path>base</path> profile
134     (<path>/usr/portage/profiles/base</path>).
135     </p>
136    
137     <p>
138 vapier 1.33 Let us take a look at this default setting for the 2004.3 profile:
139 swift 1.28 </p>
140    
141 vapier 1.33 <pre caption="Cumulative make.defaults USE variable for the 2004.3 profile">
142 swift 1.28 <comment>(This example is the sum of the settings in base, default-linux,
143     default-linux/x86 and default-linux/x86/2004.3)</comment>
144 cam 1.26 USE="x86 oss apm arts avi berkdb bitmap-fonts crypt cups encode fortran f77
145 neysx 1.38 foomaticdb gdbm gif gpm gtk imlib jpeg kde gnome libg++ libwww mad
146 cam 1.26 mikmod motif mpeg ncurses nls oggvorbis opengl pam pdflib png python qt
147     quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
148 swift 1.2 </pre>
149    
150     <p>
151     As you can see, this variable already contains quite a lot of keywords. Do
152 swift 1.25 <b>not</b> alter any <path>make.defaults</path> file to tailor
153 swift 1.2 the <c>USE</c> variable to your needs: changes in this file will be undone when
154     you update Portage!
155     </p>
156    
157     <p>
158     To change this default setting, you need to add or remove keywords to the
159     <c>USE</c> variable. This is done globally by defining the <c>USE</c> variable
160 nightmorph 1.46 in <path>/etc/make.conf</path>. In this variable you add the extra USE flags you
161     require, or remove the USE flags you don't want. This latter is done by
162 swift 1.2 prefixing the keyword with the minus-sign ("-").
163     </p>
164    
165     <p>
166     For instance, to remove support for KDE and QT but add support for ldap, the
167     following <c>USE</c> can be defined in <path>/etc/make.conf</path>:
168     </p>
169    
170     <pre caption="An example USE setting in /etc/make.conf">
171 nightmorph 1.43 USE="-kde -qt3 -qt4 ldap"
172 swift 1.2 </pre>
173    
174 swift 1.19 </body>
175     </subsection>
176     <subsection>
177     <title>Declaring USE flags for individual packages</title>
178     <body>
179    
180 swift 1.17 <p>
181     Sometimes you want to declare a certain USE flag for one (or a couple) of
182     applications but not system-wide. To accomplish this, you will need to create
183     the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
184 nightmorph 1.49 <path>/etc/portage/package.use</path>. This is usually a single file, but can
185     also be a directory; see <c>man portage</c> for more information. The following
186     examples assume <path>package.use</path> is a single file.
187 swift 1.17 </p>
188    
189     <p>
190     For instance, if you don't want <c>berkdb</c> support globally but you do want
191     it for <c>mysql</c>, you would add:
192     </p>
193    
194     <pre caption="/etc/portage/package.use example">
195     dev-db/mysql berkdb
196     </pre>
197    
198     <p>
199     You can of course also explicitly <e>disable</e> USE flags for a certain
200     application. For instance, if you don't want <c>java</c> support in PHP:
201     </p>
202    
203     <pre caption="/etc/portage/package.use 2nd example">
204     dev-php/php -java
205     </pre>
206    
207 swift 1.1 </body>
208     </subsection>
209     <subsection>
210 nightmorph 1.46 <title>Declare temporary USE flags</title>
211 swift 1.1 <body>
212    
213 swift 1.2 <p>
214 nightmorph 1.46 Sometimes you want to set a certain USE setting only once. Instead of editing
215     <path>/etc/make.conf</path> twice (to do and undo the USE changes) you can just
216     declare the USE variable as environment variable. Remember that, when you
217 swift 1.17 re-emerge or update this application (either explicitly or as part of a system
218     update) your changes will be lost!
219 swift 1.2 </p>
220    
221     <p>
222 nightmorph 1.46 As an example we will temporarily remove java from the USE setting
223 nightmorph 1.45 during the installation of seamonkey.
224 swift 1.2 </p>
225    
226 swift 1.13 <pre caption="Using USE as environment variable">
227 nightmorph 1.45 # <i>USE="-java" emerge seamonkey</i>
228 swift 1.2 </pre>
229    
230 swift 1.1 </body>
231     </subsection>
232     <subsection>
233 swift 1.15 <title>Precedence</title>
234 swift 1.2 <body>
235    
236     <p>
237 neysx 1.16 Of course there is a certain precedence on what setting has priority over the
238 swift 1.32 USE setting. You don't want to declare <c>USE="-java"</c> only to see that
239     <c>java</c> is still used due to a setting that has a higher priority.
240     The precedence for the USE setting is, ordered
241 swift 1.2 by priority (first has lowest priority):
242     </p>
243    
244     <ol>
245     <li>
246 swift 1.25 Default USE setting declared in the <path>make.defaults</path> files part of
247     your profile
248 swift 1.2 </li>
249     <li>
250     User-defined USE setting in <path>/etc/make.conf</path>
251     </li>
252     <li>
253 swift 1.17 User-defined USE setting in <path>/etc/portage/package.use</path>
254     </li>
255     <li>
256 swift 1.2 User-defined USE setting as environment variable
257     </li>
258     </ol>
259 swift 1.4
260     <p>
261 cam 1.27 To view the final <c>USE</c> setting as seen by Portage, run <c>emerge
262     --info</c>. This will list all relevant variables (including the <c>USE</c>
263     variable) with the content used by Portage.
264 swift 1.4 </p>
265    
266 cam 1.27 <pre caption="Running emerge --info">
267     # <i>emerge --info</i>
268 swift 1.4 </pre>
269 swift 1.2
270 swift 1.1 </body>
271     </subsection>
272 swift 1.12 <subsection>
273     <title>Adapting your Entire System to New USE Flags</title>
274     <body>
275    
276     <p>
277     If you have altered your USE flags and you wish to update your entire system to
278 swift 1.21 use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
279 swift 1.12 </p>
280    
281     <pre caption="Rebuilding your entire system">
282 swift 1.21 # <i>emerge --update --deep --newuse world</i>
283 swift 1.12 </pre>
284    
285     <p>
286 swift 1.20 Next, run Portage's depclean to remove the conditional dependencies that
287 swift 1.12 were emerged on your "old" system but that have been obsoleted by the new USE
288     flags.
289     </p>
290    
291     <warn>
292 cam 1.27 Running <c>emerge --depclean</c> is a dangerous operation and should be handled
293 swift 1.12 with care. Double-check the provided list of "obsoleted" packages to make sure
294     it doesn't remove packages you need. In the following example we add the
295     <c>-p</c> switch to have depclean only list the packages without removing them.
296     </warn>
297    
298     <pre caption="Removing obsoleted packages">
299 cam 1.27 # <i>emerge -p --depclean</i>
300 swift 1.12 </pre>
301    
302     <p>
303 swift 1.21 When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
304     applications that are dynamically linked against shared objects provided by
305     possibly removed packages. <c>revdep-rebuild</c> is part of the
306     <c>gentoolkit</c> package; don't forget to emerge it first.
307     </p>
308    
309     <pre caption="Running revdep-rebuild">
310     # <i>revdep-rebuild</i>
311     </pre>
312    
313     <p>
314     When all this is accomplished, your system is using the new USE flag settings.
315 swift 1.12 </p>
316    
317     </body>
318     </subsection>
319 swift 1.1 </section>
320     <section>
321 nightmorph 1.46 <title>Package specific USE flags</title>
322 swift 1.1 <subsection>
323 nightmorph 1.46 <title>Viewing available USE flags</title>
324 swift 1.1 <body>
325 swift 1.2
326     <p>
327 nightmorph 1.46 Let us take the example of <c>seamonkey</c>: what USE flags does it listen to? To
328 swift 1.21 find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
329     options:
330 swift 1.2 </p>
331    
332 nightmorph 1.46 <pre caption="Viewing the used USE flags">
333 nightmorph 1.45 # <i>emerge --pretend --verbose seamonkey</i>
334 swift 1.2 These are the packages that I would merge, in order:
335    
336     Calculating dependencies ...done!
337 nightmorph 1.45 [ebuild R ] www-client/seamonkey-1.0.7 USE="crypt gnome java -debug -ipv6
338     -ldap -mozcalendar -mozdevelop -moznocompose -moznoirc -moznomail -moznopango
339     -moznoroaming -postgres -xinerama -xprint" 0 kB
340 swift 1.2 </pre>
341    
342     <p>
343     <c>emerge</c> isn't the only tool for this job. In fact, we have a tool
344 swift 1.30 dedicated to package information called <c>equery</c> which resides in the
345 swift 1.2 <c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
346     </p>
347    
348     <pre caption="Installing gentoolkit">
349 swift 1.21 # <i>emerge gentoolkit</i>
350 swift 1.2 </pre>
351    
352     <p>
353 nightmorph 1.46 Now run <c>equery</c> with the <c>uses</c> argument to view the USE flags of a
354 swift 1.2 certain package. For instance, for the <c>gnumeric</c> package:
355     </p>
356    
357 nightmorph 1.46 <pre caption="Using equery to view used USE flags">
358 neysx 1.48 # <i>equery --nocolor uses =gnumeric-1.6.3 -a</i>
359 rane 1.42 [ Searching for packages matching =gnumeric-1.6.3... ]
360 neysx 1.48 [ Colour Code : set unset ]
361     [ Legend : Left column (U) - USE flags from make.conf ]
362     [ : Right column (I) - USE flags packages was installed with ]
363 rane 1.42 [ Found these USE variables for app-office/gnumeric-1.6.3 ]
364     U I
365 neysx 1.48 - - debug : Enable extra debug codepaths, like asserts and extra output.
366     If you want to get meaningful backtraces see
367     http://www.gentoo.org/proj/en/qa/backtraces.xml .
368     + + gnome : Adds GNOME support
369     + + python : Adds support/bindings for the Python language
370     - - static : !!do not set this during bootstrap!! Causes binaries to be
371     statically linked instead of dynamically
372 swift 1.2 </pre>
373 swift 1.1
374     </body>
375     </subsection>
376     </section>
377     </sections>

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