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general Qt USE flag cleanup

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 1.43 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.42 2006/09/04 11:29:36 rane Exp $ -->
8 swift 1.1
9     <sections>
10 swift 1.22
11 nightmorph 1.43 <version>1.35</version>
12     <date>2006-10-08</date>
13 swift 1.22
14 swift 1.1 <section>
15     <title>What are USE-flags?</title>
16     <subsection>
17     <title>The ideas behind USE-flags</title>
18     <body>
19    
20 swift 1.2 <p>
21     When you are installing Gentoo (or any other distribution, or even operating
22     system for that matter) you make choices depending on the environment you are
23     working with. A setup for a server differs from a setup for a workstation.
24     A gaming workstation differs from a 3D rendering workstation.
25     </p>
26    
27     <p>
28     This is not only true for choosing what packages you want to install, but also
29     what features a certain package should support. If you don't need OpenGL, why
30     would you bother installing OpenGL and build OpenGL support in most of your
31     packages? If you don't want to use KDE, why would you bother compiling packages
32 swift 1.5 with KDE-support if those packages work flawlessly without?
33 swift 1.2 </p>
34    
35     <p>
36     To help users in deciding what to install/activate and what not, we wanted the
37 swift 1.10 user to specify his/her environment in an easy way. This forces the user into
38 swift 1.11 deciding what they really want and eases the process for Portage, our package
39 nightmorph 1.40 management system, to make useful decisions.
40 swift 1.2 </p>
41    
42 swift 1.1 </body>
43     </subsection>
44     <subsection>
45     <title>Definition of a USE-flag</title>
46     <body>
47    
48 swift 1.2 <p>
49     Enter the USE-flags. Such a flag is a keyword that embodies support and
50     dependency-information for a certain concept. If you define a certain USE-flag,
51 swift 1.3 Portage will know that you want support for the chosen keyword. Of course
52 swift 1.2 this also alters the dependency information for a package.
53     </p>
54    
55     <p>
56 swift 1.6 Let us take a look at a specific example: the <c>kde</c> keyword. If you do not
57 swift 1.2 have this keyword in your <c>USE</c> variable, all packages that have
58     <e>optional</e> KDE support will be compiled <e>without</e> KDE support. All
59     packages that have an <e>optional</e> KDE dependency will be installed
60     <e>without</e> installing the KDE libraries (as dependency). If you have defined
61     the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
62     support, and the KDE libraries will be installed as dependency.
63     </p>
64    
65     <p>
66     By correctly defining the keywords you will receive a system tailored
67     specifically to your needs.
68     </p>
69    
70 swift 1.1 </body>
71     </subsection>
72     <subsection>
73     <title>What USE-flags exist?</title>
74     <body>
75    
76 swift 1.2 <p>
77     There are two types of USE-flags: <e>global</e> and <e>local</e> USE-flags.
78     </p>
79    
80     <ul>
81     <li>
82     A <e>global</e> USE-flag is used by several packages, system-wide. This is
83     what most people see as USE-flags.
84     </li>
85     <li>
86 swift 1.8 A <e>local</e> USE-flag is used by a single package to make package-specific
87 swift 1.2 decisions.
88     </li>
89     </ul>
90    
91     <p>
92     A list of available global USE-flags can be found <uri
93     link="/dyn/use-index.xml">online</uri> or locally in
94 neysx 1.38 <path>/usr/portage/profiles/use.desc</path>.
95 swift 1.2 </p>
96    
97 swift 1.18 <p>
98     A list of available local USE-flags can be found locally in
99     <path>/usr/portage/profiles/use.local.desc</path>.
100     </p>
101    
102 swift 1.1 </body>
103     </subsection>
104     </section>
105     <section>
106     <title>Using USE-flags</title>
107     <subsection>
108     <title>Declare permanent USE-flags</title>
109     <body>
110    
111 swift 1.2 <p>
112     In the hope you are convinced of the importance of USE-flags we will now inform
113     you how to declare USE-flags.
114     </p>
115    
116     <p>
117     As previously mentioned, all USE-flags are declared inside the <c>USE</c>
118     variable. To make it easy for users to search and pick USE-flags, we already
119     provide a <e>default</e> USE setting. This setting is a collection of USE-flags
120     we think are commonly used by the Gentoo users. This default setting is declared
121 swift 1.28 in the <path>make.defaults</path> files part of your profile.
122 swift 1.2 </p>
123    
124 swift 1.28 <p>
125     The profile your system listens to is pointed to by the
126     <path>/etc/make.profile</path> symlink. Each profile works on top of another,
127     larger profile, the end result is therefore the sum of all profiles. The top
128     profile is the <path>base</path> profile
129     (<path>/usr/portage/profiles/base</path>).
130     </p>
131    
132     <p>
133 vapier 1.33 Let us take a look at this default setting for the 2004.3 profile:
134 swift 1.28 </p>
135    
136 vapier 1.33 <pre caption="Cumulative make.defaults USE variable for the 2004.3 profile">
137 swift 1.28 <comment>(This example is the sum of the settings in base, default-linux,
138     default-linux/x86 and default-linux/x86/2004.3)</comment>
139 cam 1.26 USE="x86 oss apm arts avi berkdb bitmap-fonts crypt cups encode fortran f77
140 neysx 1.38 foomaticdb gdbm gif gpm gtk imlib jpeg kde gnome libg++ libwww mad
141 cam 1.26 mikmod motif mpeg ncurses nls oggvorbis opengl pam pdflib png python qt
142     quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
143 swift 1.2 </pre>
144    
145     <p>
146     As you can see, this variable already contains quite a lot of keywords. Do
147 swift 1.25 <b>not</b> alter any <path>make.defaults</path> file to tailor
148 swift 1.2 the <c>USE</c> variable to your needs: changes in this file will be undone when
149     you update Portage!
150     </p>
151    
152     <p>
153     To change this default setting, you need to add or remove keywords to the
154     <c>USE</c> variable. This is done globally by defining the <c>USE</c> variable
155     in <path>/etc/make.conf</path>. In this variable you add the extra USE-flags you
156     require, or remove the USE-flags you don't want. This latter is done by
157     prefixing the keyword with the minus-sign ("-").
158     </p>
159    
160     <p>
161     For instance, to remove support for KDE and QT but add support for ldap, the
162     following <c>USE</c> can be defined in <path>/etc/make.conf</path>:
163     </p>
164    
165     <pre caption="An example USE setting in /etc/make.conf">
166 nightmorph 1.43 USE="-kde -qt3 -qt4 ldap"
167 swift 1.2 </pre>
168    
169 swift 1.19 </body>
170     </subsection>
171     <subsection>
172     <title>Declaring USE flags for individual packages</title>
173     <body>
174    
175 swift 1.17 <p>
176     Sometimes you want to declare a certain USE flag for one (or a couple) of
177     applications but not system-wide. To accomplish this, you will need to create
178     the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
179     <path>/etc/portage/package.use</path>.
180     </p>
181    
182     <p>
183     For instance, if you don't want <c>berkdb</c> support globally but you do want
184     it for <c>mysql</c>, you would add:
185     </p>
186    
187     <pre caption="/etc/portage/package.use example">
188     dev-db/mysql berkdb
189     </pre>
190    
191     <p>
192     You can of course also explicitly <e>disable</e> USE flags for a certain
193     application. For instance, if you don't want <c>java</c> support in PHP:
194     </p>
195    
196     <pre caption="/etc/portage/package.use 2nd example">
197     dev-php/php -java
198     </pre>
199    
200 swift 1.1 </body>
201     </subsection>
202     <subsection>
203     <title>Declare temporary USE-flags</title>
204     <body>
205    
206 swift 1.2 <p>
207     Sometimes you want to set a certain USE-setting only once. Instead of editing
208     <path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just
209 swift 1.17 declare the USE-variable as environment variable. Remember that, when you
210     re-emerge or update this application (either explicitly or as part of a system
211     update) your changes will be lost!
212 swift 1.2 </p>
213    
214     <p>
215     As an example we will temporarily remove java from the USE-setting
216     during the installation of mozilla.
217     </p>
218    
219 swift 1.13 <pre caption="Using USE as environment variable">
220 swift 1.2 # <i>USE="-java" emerge mozilla</i>
221     </pre>
222    
223 swift 1.1 </body>
224     </subsection>
225     <subsection>
226 swift 1.15 <title>Precedence</title>
227 swift 1.2 <body>
228    
229     <p>
230 neysx 1.16 Of course there is a certain precedence on what setting has priority over the
231 swift 1.32 USE setting. You don't want to declare <c>USE="-java"</c> only to see that
232     <c>java</c> is still used due to a setting that has a higher priority.
233     The precedence for the USE setting is, ordered
234 swift 1.2 by priority (first has lowest priority):
235     </p>
236    
237     <ol>
238     <li>
239 swift 1.25 Default USE setting declared in the <path>make.defaults</path> files part of
240     your profile
241 swift 1.2 </li>
242     <li>
243     User-defined USE setting in <path>/etc/make.conf</path>
244     </li>
245     <li>
246 swift 1.17 User-defined USE setting in <path>/etc/portage/package.use</path>
247     </li>
248     <li>
249 swift 1.2 User-defined USE setting as environment variable
250     </li>
251     </ol>
252 swift 1.4
253     <p>
254 cam 1.27 To view the final <c>USE</c> setting as seen by Portage, run <c>emerge
255     --info</c>. This will list all relevant variables (including the <c>USE</c>
256     variable) with the content used by Portage.
257 swift 1.4 </p>
258    
259 cam 1.27 <pre caption="Running emerge --info">
260     # <i>emerge --info</i>
261 swift 1.4 </pre>
262 swift 1.2
263 swift 1.1 </body>
264     </subsection>
265 swift 1.12 <subsection>
266     <title>Adapting your Entire System to New USE Flags</title>
267     <body>
268    
269     <p>
270     If you have altered your USE flags and you wish to update your entire system to
271 swift 1.21 use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
272 swift 1.12 </p>
273    
274     <pre caption="Rebuilding your entire system">
275 swift 1.21 # <i>emerge --update --deep --newuse world</i>
276 swift 1.12 </pre>
277    
278     <p>
279 swift 1.20 Next, run Portage's depclean to remove the conditional dependencies that
280 swift 1.12 were emerged on your "old" system but that have been obsoleted by the new USE
281     flags.
282     </p>
283    
284     <warn>
285 cam 1.27 Running <c>emerge --depclean</c> is a dangerous operation and should be handled
286 swift 1.12 with care. Double-check the provided list of "obsoleted" packages to make sure
287     it doesn't remove packages you need. In the following example we add the
288     <c>-p</c> switch to have depclean only list the packages without removing them.
289     </warn>
290    
291     <pre caption="Removing obsoleted packages">
292 cam 1.27 # <i>emerge -p --depclean</i>
293 swift 1.12 </pre>
294    
295     <p>
296 swift 1.21 When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
297     applications that are dynamically linked against shared objects provided by
298     possibly removed packages. <c>revdep-rebuild</c> is part of the
299     <c>gentoolkit</c> package; don't forget to emerge it first.
300     </p>
301    
302     <pre caption="Running revdep-rebuild">
303     # <i>revdep-rebuild</i>
304     </pre>
305    
306     <p>
307     When all this is accomplished, your system is using the new USE flag settings.
308 swift 1.12 </p>
309    
310     </body>
311     </subsection>
312 swift 1.1 </section>
313     <section>
314     <title>Package specific USE-flags</title>
315     <subsection>
316 swift 1.2 <title>Viewing available USE-flags</title>
317 swift 1.1 <body>
318 swift 1.2
319     <p>
320     Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To
321 swift 1.21 find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
322     options:
323 swift 1.2 </p>
324    
325     <pre caption="Viewing the used USE-flags">
326     # <i>emerge --pretend --verbose mozilla</i>
327     These are the packages that I would merge, in order:
328    
329     Calculating dependencies ...done!
330 neysx 1.38 [ebuild R ] www-client/mozilla-1.7.12-r2 USE="crypt gnome java mozsvg ssl
331     truetype xprint -debug -ipv6 -ldap -mozcalendar -mozdevelop -moznocompose
332     -moznoirc -moznomail -moznoxft -postgres -xinerama" 0 kB
333 swift 1.2 </pre>
334    
335     <p>
336     <c>emerge</c> isn't the only tool for this job. In fact, we have a tool
337 swift 1.30 dedicated to package information called <c>equery</c> which resides in the
338 swift 1.2 <c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
339     </p>
340    
341     <pre caption="Installing gentoolkit">
342 swift 1.21 # <i>emerge gentoolkit</i>
343 swift 1.2 </pre>
344    
345     <p>
346 swift 1.30 Now run <c>equery</c> with the <c>uses</c> argument to view the USE-flags of a
347 swift 1.2 certain package. For instance, for the <c>gnumeric</c> package:
348     </p>
349    
350 swift 1.30 <pre caption="Using equery to view used USE-flags">
351 rane 1.42 # <i>equery uses =gnumeric-1.6.3 -a</i>
352     [ Searching for packages matching =gnumeric-1.6.3... ]
353     [ Colour Code : <comment>set</comment> <i>unset</i> ]
354     [ Legend : Left column (U) - USE flags from make.conf ]
355     [ : Right column (I) - USE flags packages was installed with ]
356     [ Found these USE variables for app-office/gnumeric-1.6.3 ]
357     U I
358     - - <i>debug</i> : Tells configure and the makefiles to build for debugging.
359     Effects vary across packages, but generally it will at
360     least add -g to CFLAGS. Remember to set FEATURES=nostrip too
361     - - <i>gnome</i> : Adds GNOME support
362     + + <comment>python</comment> : Adds support/bindings for the Python language
363     - - <i>static</i> : !!do not set this during bootstrap!! Causes binaries to be
364     statically linked instead of dynamically
365 swift 1.2 </pre>
366 swift 1.1
367     </body>
368     </subsection>
369     </section>
370     </sections>

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