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2<!DOCTYPE sections SYSTEM "/dtd/book.dtd">
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4<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.5 2003/12/16 18:08:56 swift Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.48 2007/07/04 13:47:19 neysx Exp $ -->
5 8
6<sections> 9<sections>
10
11<abstract>
12USE flags are a very important aspect of Gentoo. In this chapter, you learn to
13work with USE flags and understand how USE flags interact with your system.
14</abstract>
15
16<version>1.37</version>
17<date>2007-07-04</date>
18
7<section> 19<section>
8<title>What are USE-flags?</title> 20<title>What are USE flags?</title>
9<subsection> 21<subsection>
10<title>The ideas behind USE-flags</title> 22<title>The ideas behind USE flags</title>
11<body> 23<body>
12 24
13<p> 25<p>
14When you are installing Gentoo (or any other distribution, or even operating 26When you are installing Gentoo (or any other distribution, or even operating
15system for that matter) you make choices depending on the environment you are 27system for that matter) you make choices depending on the environment you are
20<p> 32<p>
21This is not only true for choosing what packages you want to install, but also 33This is not only true for choosing what packages you want to install, but also
22what features a certain package should support. If you don't need OpenGL, why 34what features a certain package should support. If you don't need OpenGL, why
23would you bother installing OpenGL and build OpenGL support in most of your 35would you bother installing OpenGL and build OpenGL support in most of your
24packages? If you don't want to use KDE, why would you bother compiling packages 36packages? If you don't want to use KDE, why would you bother compiling packages
25with KDE-support if those packages work flawlessly without? 37with KDE support if those packages work flawlessly without?
26</p> 38</p>
27 39
28<p> 40<p>
29To help users in deciding what to install/activate and what not, we wanted the 41To help users in deciding what to install/activate and what not, we wanted the
30user to specify his environment in an easy way. This forces the user into 42user to specify his/her environment in an easy way. This forces the user into
31deciding what he really wants and eases the process for Portage, our package 43deciding what they really want and eases the process for Portage, our package
32managment system, to make useful decisions. 44management system, to make useful decisions.
33</p> 45</p>
34 46
35</body> 47</body>
36</subsection>
37<subsection> 48</subsection>
49<subsection>
38<title>Definition of a USE-flag</title> 50<title>Definition of a USE flag</title>
39<body> 51<body>
40 52
41<p> 53<p>
42Enter the USE-flags. Such a flag is a keyword that embodies support and 54Enter the USE flags. Such a flag is a keyword that embodies support and
43dependency-information for a certain concept. If you define a certain USE-flag, 55dependency-information for a certain concept. If you define a certain USE flag,
44Portage will know that you want support for the chosen keyword. Of course 56Portage will know that you want support for the chosen keyword. Of course
45this also alters the dependency information for a package. 57this also alters the dependency information for a package.
46</p> 58</p>
47 59
48<p> 60<p>
49Lets take a look at a specific example: the <c>kde</c> keyword. If you do not 61Let us take a look at a specific example: the <c>kde</c> keyword. If you do not
50have this keyword in your <c>USE</c> variable, all packages that have 62have this keyword in your <c>USE</c> variable, all packages that have
51<e>optional</e> KDE support will be compiled <e>without</e> KDE support. All 63<e>optional</e> KDE support will be compiled <e>without</e> KDE support. All
52packages that have an <e>optional</e> KDE dependency will be installed 64packages that have an <e>optional</e> KDE dependency will be installed
53<e>without</e> installing the KDE libraries (as dependency). If you have defined 65<e>without</e> installing the KDE libraries (as dependency). If you have defined
54the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE 66the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
61</p> 73</p>
62 74
63</body> 75</body>
64</subsection> 76</subsection>
65<subsection> 77<subsection>
66<title>What USE-flags exist?</title> 78<title>What USE flags exist?</title>
67<body> 79<body>
68 80
69<p> 81<p>
70There are two types of USE-flags: <e>global</e> and <e>local</e> USE-flags. 82There are two types of USE flags: <e>global</e> and <e>local</e> USE flags.
71</p> 83</p>
72 84
73<ul> 85<ul>
74 <li> 86 <li>
75 A <e>global</e> USE-flag is used by several packages, system-wide. This is 87 A <e>global</e> USE flag is used by several packages, system-wide. This is
76 what most people see as USE-flags. 88 what most people see as USE flags.
77 </li>
78 <li> 89 </li>
90 <li>
79 A <e>local</e> USE-fag is used by a single package to make package-specific 91 A <e>local</e> USE flag is used by a single package to make package-specific
80 decisions. 92 decisions.
81 </li> 93 </li>
82</ul> 94</ul>
83 95
84<p> 96<p>
85A list of available global USE-flags can be found <uri 97A list of available global USE flags can be found <uri
86link="/dyn/use-index.xml">online</uri> or locally in 98link="/dyn/use-index.xml">online</uri> or locally in
87<path>/usr/portage/profiles/use.desc</path>. A short (<e>very</e> incomplete) 99<path>/usr/portage/profiles/use.desc</path>.
88snippet: 100</p>
101
89</p> 102<p>
90 103A list of available local USE flags can be found locally in
91<pre caption="A short snippet of available USE-flags"> 104<path>/usr/portage/profiles/use.local.desc</path>.
92gtk - Adds support for x11-libs/gtk+ (The GIMP Toolkit)
93gtk2 - Use gtk+-2.0.0 over gtk+-1.2 in cases where a program supports both.
94gtkhtml - Adds support for gnome-extra/gtkhtml
95guile - Adds support for dev-util/guile (interpreter for Scheme)
96icc - Use the Intel C++ Compiler if the package supports it
97icc-pgo - Enable PGO data generation or use when use icc.
98imap - Adds support for IMAP
99</pre> 105</p>
100 106
101</body> 107</body>
102</subsection> 108</subsection>
103</section> 109</section>
104<section> 110<section>
105<title>Using USE-flags</title> 111<title>Using USE flags</title>
106<subsection> 112<subsection>
107<title>Declare permanent USE-flags</title> 113<title>Declare permanent USE flags</title>
108<body> 114<body>
109 115
110<p> 116<p>
111In the hope you are convinced of the importance of USE-flags we will now inform 117In the hope you are convinced of the importance of USE flags we will now inform
112you how to declare USE-flags. 118you how to declare USE flags.
113</p>
114
115<p> 119</p>
120
121<p>
116As previously mentioned, all USE-flags are declared inside the <c>USE</c> 122As previously mentioned, all USE flags are declared inside the <c>USE</c>
117variable. To make it easy for users to search and pick USE-flags, we already 123variable. To make it easy for users to search and pick USE flags, we already
118provide a <e>default</e> USE setting. This setting is a collection of USE-flags 124provide a <e>default</e> USE setting. This setting is a collection of USE flags
119we think are commonly used by the Gentoo users. This default setting is declared 125we think are commonly used by the Gentoo users. This default setting is declared
120in the <path>/etc/make.profile/make.defaults</path> file. Let us take a look at 126in the <path>make.defaults</path> files part of your profile.
121this default setting: 127</p>
128
122</p> 129<p>
130The profile your system listens to is pointed to by the
131<path>/etc/make.profile</path> symlink. Each profile works on top of another,
132larger profile, the end result is therefore the sum of all profiles. The top
133profile is the <path>base</path> profile
134(<path>/usr/portage/profiles/base</path>).
135</p>
123 136
124<pre caption="/etc/make.profile/make.defaults USE variable"> 137<p>
125USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm gtk 138Let us take a look at this default setting for the 2004.3 profile:
126 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses nls 139</p>
127 oggvorbis opengl pam pdflib png python qt quicktime readline sdl slang 140
141<pre caption="Cumulative make.defaults USE variable for the 2004.3 profile">
142<comment>(This example is the sum of the settings in base, default-linux,
143 default-linux/x86 and default-linux/x86/2004.3)</comment>
144USE="x86 oss apm arts avi berkdb bitmap-fonts crypt cups encode fortran f77
145 foomaticdb gdbm gif gpm gtk imlib jpeg kde gnome libg++ libwww mad
146 mikmod motif mpeg ncurses nls oggvorbis opengl pam pdflib png python qt
128 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 147 quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
129</pre> 148</pre>
130 149
131<p> 150<p>
132As you can see, this variable already contains quite a lot of keywords. Do 151As you can see, this variable already contains quite a lot of keywords. Do
133<b>not</b> alter the <path>/etc/make.profile/make.defaults</path> file to tailor 152<b>not</b> alter any <path>make.defaults</path> file to tailor
134the <c>USE</c> variable to your needs: changes in this file will be undone when 153the <c>USE</c> variable to your needs: changes in this file will be undone when
135you update Portage! 154you update Portage!
136</p> 155</p>
137 156
138<p> 157<p>
139To change this default setting, you need to add or remove keywords to the 158To change this default setting, you need to add or remove keywords to the
140<c>USE</c> variable. This is done globally by defining the <c>USE</c> variable 159<c>USE</c> variable. This is done globally by defining the <c>USE</c> variable
141in <path>/etc/make.conf</path>. In this variable you add the extra USE-flags you 160in <path>/etc/make.conf</path>. In this variable you add the extra USE flags you
142require, or remove the USE-flags you don't want. This latter is done by 161require, or remove the USE flags you don't want. This latter is done by
143prefixing the keyword with the minus-sign ("-"). 162prefixing the keyword with the minus-sign ("-").
144</p> 163</p>
145 164
146<p> 165<p>
147For instance, to remove support for KDE and QT but add support for ldap, the 166For instance, to remove support for KDE and QT but add support for ldap, the
148following <c>USE</c> can be defined in <path>/etc/make.conf</path>: 167following <c>USE</c> can be defined in <path>/etc/make.conf</path>:
149</p> 168</p>
150 169
151<pre caption="An example USE setting in /etc/make.conf"> 170<pre caption="An example USE setting in /etc/make.conf">
152USE="-kde -qt ldap" 171USE="-kde -qt3 -qt4 ldap"
153</pre> 172</pre>
154 173
155</body> 174</body>
156</subsection>
157<subsection> 175</subsection>
176<subsection>
177<title>Declaring USE flags for individual packages</title>
178<body>
179
180<p>
181Sometimes you want to declare a certain USE flag for one (or a couple) of
182applications but not system-wide. To accomplish this, you will need to create
183the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
184<path>/etc/portage/package.use</path>.
185</p>
186
187<p>
188For instance, if you don't want <c>berkdb</c> support globally but you do want
189it for <c>mysql</c>, you would add:
190</p>
191
192<pre caption="/etc/portage/package.use example">
193dev-db/mysql berkdb
194</pre>
195
196<p>
197You can of course also explicitly <e>disable</e> USE flags for a certain
198application. For instance, if you don't want <c>java</c> support in PHP:
199</p>
200
201<pre caption="/etc/portage/package.use 2nd example">
202dev-php/php -java
203</pre>
204
205</body>
206</subsection>
207<subsection>
158<title>Declare temporary USE-flags</title> 208<title>Declare temporary USE flags</title>
159<body> 209<body>
160 210
161<p> 211<p>
162Sometimes you want to set a certain USE-setting only once. Instead of editing 212Sometimes you want to set a certain USE setting only once. Instead of editing
163<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just 213<path>/etc/make.conf</path> twice (to do and undo the USE changes) you can just
164declare the USE-variable as environment variable. 214declare the USE variable as environment variable. Remember that, when you
165</p> 215re-emerge or update this application (either explicitly or as part of a system
166 216update) your changes will be lost!
167<p> 217</p>
218
219<p>
168As an example we will temporarily remove java from the USE-setting 220As an example we will temporarily remove java from the USE setting
169during the installation of mozilla. 221during the installation of seamonkey.
170</p> 222</p>
171 223
172<note>
173The <c>emerge</c> command will be discussed more thoroughly in <uri
174link="?part=2&amp;chap=2">Portage and Software</uri>.
175</note>
176
177<pre caption="Using USE as evironment variable"> 224<pre caption="Using USE as environment variable">
178# <i>USE="-java" emerge mozilla</i> 225# <i>USE="-java" emerge seamonkey</i>
179</pre> 226</pre>
180 227
181</body> 228</body>
182</subsection>
183<subsection> 229</subsection>
184<title>Inheriting USE-flags</title>
185<body>
186
187<p>
188Some packages don't only listen to USE-flags, but also provide USE-flags. When
189you install such a package, the USE-flag they provide is added to your USE
190setting. To view the list of packages that provide a USE-flag, check
191<path>/etc/make.profile/use.defaults</path>:
192</p>
193
194<pre caption="A snippet from /etc/make.profile/use.defaults">
195gnome gnome-base/gnome
196gtk x11-libs/gtk+
197qt x11-libs/qt
198kde kde-base/kdebase
199motif x11-libs/openmotif
200</pre>
201
202</body>
203</subsection> 230<subsection>
204<subsection>
205<title>Precendence</title> 231<title>Precedence</title>
206<body> 232<body>
207 233
208<p> 234<p>
209Of course there is a certain precendence on what setting has priority over the 235Of course there is a certain precedence on what setting has priority over the
210USE setting. You don't want to declare <c>USE="-java"</c> only to see that 236USE setting. You don't want to declare <c>USE="-java"</c> only to see that
211<c>java</c> is declared anyway. The precedence for the USE setting is, ordered 237<c>java</c> is still used due to a setting that has a higher priority.
238The precedence for the USE setting is, ordered
212by priority (first has lowest priority): 239by priority (first has lowest priority):
213</p> 240</p>
214 241
215<ol> 242<ol>
216 <li> 243 <li>
217 Default USE setting declared in <path>/etc/make.profile/make.defaults</path> 244 Default USE setting declared in the <path>make.defaults</path> files part of
218 </li> 245 your profile
219 <li>
220 Inherited USE setting if a package from
221 <path>/etc/make.profile/use.defaults</path> is installed
222 </li> 246 </li>
223 <li> 247 <li>
224 User-defined USE setting in <path>/etc/make.conf</path> 248 User-defined USE setting in <path>/etc/make.conf</path>
225 </li> 249 </li>
226 <li> 250 <li>
251 User-defined USE setting in <path>/etc/portage/package.use</path>
252 </li>
253 <li>
227 User-defined USE setting as environment variable 254 User-defined USE setting as environment variable
228 </li> 255 </li>
229</ol> 256</ol>
230 257
231<p> 258<p>
232To view the final <c>USE</c> setting as seen by Portage, run <c>emerge info</c>. 259To view the final <c>USE</c> setting as seen by Portage, run <c>emerge
233This will list all relevant variables (including the <c>USE</c> variable) with 260--info</c>. This will list all relevant variables (including the <c>USE</c>
234the content used by Portage. 261variable) with the content used by Portage.
235</p> 262</p>
236 263
237<pre caption="Running emerge info"> 264<pre caption="Running emerge --info">
238# <i>emerge info</i> 265# <i>emerge --info</i>
266</pre>
267
268</body>
269</subsection>
270<subsection>
271<title>Adapting your Entire System to New USE Flags</title>
272<body>
273
274<p>
275If you have altered your USE flags and you wish to update your entire system to
276use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
239</pre> 277</p>
278
279<pre caption="Rebuilding your entire system">
280# <i>emerge --update --deep --newuse world</i>
281</pre>
282
283<p>
284Next, run Portage's depclean to remove the conditional dependencies that
285were emerged on your "old" system but that have been obsoleted by the new USE
286flags.
287</p>
288
289<warn>
290Running <c>emerge --depclean</c> is a dangerous operation and should be handled
291with care. Double-check the provided list of "obsoleted" packages to make sure
292it doesn't remove packages you need. In the following example we add the
293<c>-p</c> switch to have depclean only list the packages without removing them.
294</warn>
295
296<pre caption="Removing obsoleted packages">
297# <i>emerge -p --depclean</i>
298</pre>
299
300<p>
301When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
302applications that are dynamically linked against shared objects provided by
303possibly removed packages. <c>revdep-rebuild</c> is part of the
304<c>gentoolkit</c> package; don't forget to emerge it first.
305</p>
306
307<pre caption="Running revdep-rebuild">
308# <i>revdep-rebuild</i>
309</pre>
310
311<p>
312When all this is accomplished, your system is using the new USE flag settings.
313</p>
240 314
241</body> 315</body>
242</subsection> 316</subsection>
243</section> 317</section>
244<section> 318<section>
245<title>Package specific USE-flags</title> 319<title>Package specific USE flags</title>
246<subsection> 320<subsection>
247<title>Viewing available USE-flags</title> 321<title>Viewing available USE flags</title>
248<body> 322<body>
249 323
250<p>
251In the next chapter on <uri link="?part=2&amp;chap=2">Portage and Software</uri>
252we will explain how to manage your installed software and how to work with
253<c>emerge</c>. However, we will give you a primer on <c>emerge</c> by showing
254you how to view what USE-flags a package uses.
255</p> 324<p>
256
257<p>
258Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To 325Let us take the example of <c>seamonkey</c>: what USE flags does it listen to? To
259find out, we use <c>emerge</c> with the <c>--pretend</c> (don't really do 326find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
260anything) and <c>--verbose</c> (give more output) options: 327options:
261</p> 328</p>
262 329
263<pre caption="Viewing the used USE-flags"> 330<pre caption="Viewing the used USE flags">
264# <i>emerge --pretend --verbose mozilla</i> 331# <i>emerge --pretend --verbose seamonkey</i>
265These are the packages that I would merge, in order: 332These are the packages that I would merge, in order:
266 333
267Calculating dependencies ...done! 334Calculating dependencies ...done!
268[ebuild N ] net-www/mozilla-1.5-r1 +java +crypt -ipv6 -gtk2 +ssl +ldap 335[ebuild R ] www-client/seamonkey-1.0.7 USE="crypt gnome java -debug -ipv6
269+gnome -debug +mozcalendar -mozaccess -mozxmlterm -moznoirc -moznomail 336-ldap -mozcalendar -mozdevelop -moznocompose -moznoirc -moznomail -moznopango
270-moznocompose -moznoxft 337-moznoroaming -postgres -xinerama -xprint" 0 kB
271</pre> 338</pre>
272 339
273<p> 340<p>
274<c>emerge</c> isn't the only tool for this job. In fact, we have a tool 341<c>emerge</c> isn't the only tool for this job. In fact, we have a tool
275dedicated to package information called <c>etcat</c> which resides in the 342dedicated to package information called <c>equery</c> which resides in the
276<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 343<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
277</p> 344</p>
278 345
279<pre caption="Installing gentoolkit"> 346<pre caption="Installing gentoolkit">
280# <i>emerge --usepkg gentoolkit</i> 347# <i>emerge gentoolkit</i>
281</pre> 348</pre>
282 349
283<p> 350<p>
284Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a 351Now run <c>equery</c> with the <c>uses</c> argument to view the USE flags of a
285certain package. For instance, for the <c>gnumeric</c> package: 352certain package. For instance, for the <c>gnumeric</c> package:
286</p> 353</p>
287 354
288<pre caption="Using etcat to view used USE-flags"> 355<pre caption="Using equery to view used USE flags">
289# <i>etcat uses gnumeric</i> 356# <i>equery --nocolor uses =gnumeric-1.6.3 -a</i>
290[ Colour Code : <i>set</i> <comment>unset</comment> ] 357[ Searching for packages matching =gnumeric-1.6.3... ]
291[ Legend : (U) Col 1 - Current USE flags ] 358[ Colour Code : set unset ]
292[ : (I) Col 2 - Installed With USE flags ] 359[ Legend : Left column (U) - USE flags from make.conf ]
293 360[ : Right column (I) - USE flags packages was installed with ]
294 U I [ Found these USE variables in : app-office/gnumeric-1.2.0 ] 361[ Found these USE variables for app-office/gnumeric-1.6.3 ]
295 - - <comment>libgda</comment> : Adds GNU Data Access (CORBA wrapper) support for gnumeric 362 U I
296 - - <comment>gnomedb</comment> : unknown 363 - - debug : Enable extra debug codepaths, like asserts and extra output.
364 If you want to get meaningful backtraces see
365 http://www.gentoo.org/proj/en/qa/backtraces.xml .
366 + + gnome : Adds GNOME support
297 + + <i>python</i> : Adds support/bindings for the Python language 367 + + python : Adds support/bindings for the Python language
298 + + <i>bonobo</i> : Adds support for gnome-base/bonobo (Gnome CORBA interfaces) 368 - - static : !!do not set this during bootstrap!! Causes binaries to be
369 statically linked instead of dynamically
299</pre> 370</pre>
300 371
301</body> 372</body>
302</subsection> 373</subsection>
303</section> 374</section>

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