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1<?xml version='1.0' encoding='UTF-8'?>
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 1.27 2005/01/22 01:24:31 cam Exp $ -->
5 8
6<sections> 9<sections>
10
11<version>1.24</version>
12<date>2005-01-22</date>
13
7<section> 14<section>
8<title>What are USE-flags?</title> 15<title>What are USE-flags?</title>
9<subsection> 16<subsection>
10<title>The ideas behind USE-flags</title> 17<title>The ideas behind USE-flags</title>
11<body> 18<body>
25with KDE-support if those packages work flawlessly without? 32with KDE-support if those packages work flawlessly without?
26</p> 33</p>
27 34
28<p> 35<p>
29To help users in deciding what to install/activate and what not, we wanted the 36To 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 37user 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 38deciding what they really want and eases the process for Portage, our package
32managment system, to make useful decisions. 39managment system, to make useful decisions.
33</p> 40</p>
34 41
35</body> 42</body>
36</subsection> 43</subsection>
44Portage will know that you want support for the chosen keyword. Of course 51Portage will know that you want support for the chosen keyword. Of course
45this also alters the dependency information for a package. 52this also alters the dependency information for a package.
46</p> 53</p>
47 54
48<p> 55<p>
49Lets take a look at a specific example: the <c>kde</c> keyword. If you do not 56Let 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 57have 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 58<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 59packages 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 60<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 61the <c>kde</c> keyword, then those packages <e>will</e> be compiled with KDE
74 <li> 81 <li>
75 A <e>global</e> USE-flag is used by several packages, system-wide. This is 82 A <e>global</e> USE-flag is used by several packages, system-wide. This is
76 what most people see as USE-flags. 83 what most people see as USE-flags.
77 </li> 84 </li>
78 <li> 85 <li>
79 A <e>local</e> USE-fag is used by a single package to make package-specific 86 A <e>local</e> USE-flag is used by a single package to make package-specific
80 decisions. 87 decisions.
81 </li> 88 </li>
82</ul> 89</ul>
83 90
84<p> 91<p>
96icc - Use the Intel C++ Compiler if the package supports it 103icc - Use the Intel C++ Compiler if the package supports it
97icc-pgo - Enable PGO data generation or use when use icc. 104icc-pgo - Enable PGO data generation or use when use icc.
98imap - Adds support for IMAP 105imap - Adds support for IMAP
99</pre> 106</pre>
100 107
108<p>
109A list of available local USE-flags can be found locally in
110<path>/usr/portage/profiles/use.local.desc</path>.
111</p>
112
101</body> 113</body>
102</subsection> 114</subsection>
103</section> 115</section>
104<section> 116<section>
105<title>Using USE-flags</title> 117<title>Using USE-flags</title>
115<p> 127<p>
116As previously mentioned, all USE-flags are declared inside the <c>USE</c> 128As 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 129variable. 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 130provide 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 131we 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 132in the <path>make.defaults</path> files part of your profile. Let us take a
121this default setting: 133look at this default setting:
122</p> 134</p>
123 135
124<pre caption="/etc/make.profile/make.defaults USE variable"> 136<pre caption="/usr/portage/profiles/default-linux/x86/2004.3/make.defaults USE variable">
125USE="x86 oss apm arts avi berkdb crypt cups encode foomaticdb gdbm gif gpm gtk 137<comment>(This is an example and might have changed since it was taken)</comment>
126 imlib jpeg kde gnome libg++ libwww mad mikmod motif mpeg ncurses nls 138USE="x86 oss apm arts avi berkdb bitmap-fonts crypt cups encode fortran f77
127 oggvorbis opengl pam pdflib png python qt quicktime readline sdl slang 139 foomaticdb gdbm gif gpm gtk gtk2 imlib jpeg kde gnome libg++ libwww mad
140 mikmod motif mpeg ncurses nls oggvorbis opengl pam pdflib png python qt
128 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 141 quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
129</pre> 142</pre>
130 143
131<p> 144<p>
132As you can see, this variable already contains quite a lot of keywords. Do 145As 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 146<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 147the <c>USE</c> variable to your needs: changes in this file will be undone when
135you update Portage! 148you update Portage!
136</p> 149</p>
137 150
138<p> 151<p>
153</pre> 166</pre>
154 167
155</body> 168</body>
156</subsection> 169</subsection>
157<subsection> 170<subsection>
171<title>Declaring USE flags for individual packages</title>
172<body>
173
174<p>
175Sometimes you want to declare a certain USE flag for one (or a couple) of
176applications but not system-wide. To accomplish this, you will need to create
177the <path>/etc/portage</path> directory (if it doesn't exist yet) and edit
178<path>/etc/portage/package.use</path>.
179</p>
180
181<p>
182For instance, if you don't want <c>berkdb</c> support globally but you do want
183it for <c>mysql</c>, you would add:
184</p>
185
186<pre caption="/etc/portage/package.use example">
187dev-db/mysql berkdb
188</pre>
189
190<p>
191You can of course also explicitly <e>disable</e> USE flags for a certain
192application. For instance, if you don't want <c>java</c> support in PHP:
193</p>
194
195<pre caption="/etc/portage/package.use 2nd example">
196dev-php/php -java
197</pre>
198
199</body>
200</subsection>
201<subsection>
158<title>Declare temporary USE-flags</title> 202<title>Declare temporary USE-flags</title>
159<body> 203<body>
160 204
161<p> 205<p>
162Sometimes you want to set a certain USE-setting only once. Instead of editing 206Sometimes 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 207<path>/etc/make.conf</path> twice (to do and undo the USE-changes) you can just
164declare the USE-variable as environment variable. 208declare the USE-variable as environment variable. Remember that, when you
209re-emerge or update this application (either explicitly or as part of a system
210update) your changes will be lost!
165</p> 211</p>
166 212
167<p> 213<p>
168As an example we will temporarily remove java from the USE-setting 214As an example we will temporarily remove java from the USE-setting
169during the installation of mozilla. 215during the installation of mozilla.
170</p> 216</p>
171 217
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"> 218<pre caption="Using USE as environment variable">
178# <i>USE="-java" emerge mozilla</i> 219# <i>USE="-java" emerge mozilla</i>
179</pre> 220</pre>
180 221
181</body> 222</body>
182</subsection> 223</subsection>
200</pre> 241</pre>
201 242
202</body> 243</body>
203</subsection> 244</subsection>
204<subsection> 245<subsection>
205<title>Precendence</title> 246<title>Precedence</title>
206<body> 247<body>
207 248
208<p> 249<p>
209Of course there is a certain precendence on what setting has priority over the 250Of 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 251USE 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 252<c>java</c> is declared anyway. The precedence for the USE setting is, ordered
212by priority (first has lowest priority): 253by priority (first has lowest priority):
213</p> 254</p>
214 255
215<ol> 256<ol>
216 <li> 257 <li>
217 Default USE setting declared in <path>/etc/make.profile/make.defaults</path> 258 Default USE setting declared in the <path>make.defaults</path> files part of
259 your profile
218 </li> 260 </li>
219 <li> 261 <li>
220 Inherited USE setting if a package from 262 Inherited USE setting if a package from
221 <path>/etc/make.profile/use.defaults</path> is installed 263 <path>/etc/make.profile/use.defaults</path> is installed
222 </li> 264 </li>
223 <li> 265 <li>
224 User-defined USE setting in <path>/etc/make.conf</path> 266 User-defined USE setting in <path>/etc/make.conf</path>
225 </li> 267 </li>
226 <li> 268 <li>
269 User-defined USE setting in <path>/etc/portage/package.use</path>
270 </li>
271 <li>
227 User-defined USE setting as environment variable 272 User-defined USE setting as environment variable
228 </li> 273 </li>
229</ol> 274</ol>
230 275
231<p> 276<p>
232To view the final <c>USE</c> setting as seen by Portage, run <c>emerge info</c>. 277To 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 278--info</c>. This will list all relevant variables (including the <c>USE</c>
234the content used by Portage. 279variable) with the content used by Portage.
235</p> 280</p>
236 281
237<pre caption="Running emerge info"> 282<pre caption="Running emerge --info">
238# <i>emerge info</i> 283# <i>emerge --info</i>
284</pre>
285
286</body>
287</subsection>
288<subsection>
289<title>Adapting your Entire System to New USE Flags</title>
290<body>
291
292<p>
293If you have altered your USE flags and you wish to update your entire system to
294use the new USE flags, use <c>emerge</c>'s <c>--newuse</c> option:
239</pre> 295</p>
296
297<pre caption="Rebuilding your entire system">
298# <i>emerge --update --deep --newuse world</i>
299</pre>
300
301<p>
302Next, run Portage's depclean to remove the conditional dependencies that
303were emerged on your "old" system but that have been obsoleted by the new USE
304flags.
305</p>
306
307<warn>
308Running <c>emerge --depclean</c> is a dangerous operation and should be handled
309with care. Double-check the provided list of "obsoleted" packages to make sure
310it doesn't remove packages you need. In the following example we add the
311<c>-p</c> switch to have depclean only list the packages without removing them.
312</warn>
313
314<pre caption="Removing obsoleted packages">
315# <i>emerge -p --depclean</i>
316</pre>
317
318<p>
319When depclean has finished, run <c>revdep-rebuild</c> to rebuild the
320applications that are dynamically linked against shared objects provided by
321possibly removed packages. <c>revdep-rebuild</c> is part of the
322<c>gentoolkit</c> package; don't forget to emerge it first.
323</p>
324
325<pre caption="Running revdep-rebuild">
326# <i>revdep-rebuild</i>
327</pre>
328
329<p>
330When all this is accomplished, your system is using the new USE flag settings.
331</p>
240 332
241</body> 333</body>
242</subsection> 334</subsection>
243</section> 335</section>
244<section> 336<section>
246<subsection> 338<subsection>
247<title>Viewing available USE-flags</title> 339<title>Viewing available USE-flags</title>
248<body> 340<body>
249 341
250<p> 342<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>
256
257<p>
258Let us take the example of <c>mozilla</c>: what USE-flags does it listen to? To 343Let us take the example of <c>mozilla</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 344find out, we use <c>emerge</c> with the <c>--pretend</c> and <c>--verbose</c>
260anything) and <c>--verbose</c> (give more output) options: 345options:
261</p> 346</p>
262 347
263<pre caption="Viewing the used USE-flags"> 348<pre caption="Viewing the used USE-flags">
264# <i>emerge --pretend --verbose mozilla</i> 349# <i>emerge --pretend --verbose mozilla</i>
265These are the packages that I would merge, in order: 350These are the packages that I would merge, in order:
275dedicated to package information called <c>etcat</c> which resides in the 360dedicated to package information called <c>etcat</c> which resides in the
276<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 361<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
277</p> 362</p>
278 363
279<pre caption="Installing gentoolkit"> 364<pre caption="Installing gentoolkit">
280# <i>emerge --usepkg gentoolkit</i> 365# <i>emerge gentoolkit</i>
281</pre> 366</pre>
282 367
283<p> 368<p>
284Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a 369Now run <c>etcat</c> with the <c>uses</c> argument to view the USE-flags of a
285certain package. For instance, for the <c>gnumeric</c> package: 370certain package. For instance, for the <c>gnumeric</c> package:

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