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7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.8 2004/01/12 20:00:39 swift Exp $ --> 7<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-working-use.xml,v 1.26 2004/12/28 20:01:06 cam Exp $ -->
8 8
9<sections> 9<sections>
10
11<version>1.23</version>
12<date>2004-12-28</date>
13
10<section> 14<section>
11<title>What are USE-flags?</title> 15<title>What are USE-flags?</title>
12<subsection> 16<subsection>
13<title>The ideas behind USE-flags</title> 17<title>The ideas behind USE-flags</title>
14<body> 18<body>
28with KDE-support if those packages work flawlessly without? 32with KDE-support if those packages work flawlessly without?
29</p> 33</p>
30 34
31<p> 35<p>
32To 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
33user 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
34deciding 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
35managment system, to make useful decisions. 39managment system, to make useful decisions.
36</p> 40</p>
37 41
38</body> 42</body>
39</subsection> 43</subsection>
99icc - Use the Intel C++ Compiler if the package supports it 103icc - Use the Intel C++ Compiler if the package supports it
100icc-pgo - Enable PGO data generation or use when use icc. 104icc-pgo - Enable PGO data generation or use when use icc.
101imap - Adds support for IMAP 105imap - Adds support for IMAP
102</pre> 106</pre>
103 107
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
104</body> 113</body>
105</subsection> 114</subsection>
106</section> 115</section>
107<section> 116<section>
108<title>Using USE-flags</title> 117<title>Using USE-flags</title>
118<p> 127<p>
119As 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>
120variable. 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
121provide 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
122we 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
123in 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
124this default setting: 133look at this default setting:
125</p> 134</p>
126 135
127<pre caption="/etc/make.profile/make.defaults USE variable"> 136<pre caption="/usr/portage/profiles/default-linux/x86/2004.3/make.defaults USE variable">
128USE="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>
129 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
130 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
131 spell ssl svga tcpd truetype X xml2 xmms xv zlib" 141 quicktime readline sdl spell ssl svga tcpd truetype X xml2 xmms xv zlib"
132</pre> 142</pre>
133 143
134<p> 144<p>
135As 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
136<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
137the <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
138you update Portage! 148you update Portage!
139</p> 149</p>
140 150
141<p> 151<p>
156</pre> 166</pre>
157 167
158</body> 168</body>
159</subsection> 169</subsection>
160<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>
161<title>Declare temporary USE-flags</title> 202<title>Declare temporary USE-flags</title>
162<body> 203<body>
163 204
164<p> 205<p>
165Sometimes 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
166<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
167declare 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!
168</p> 211</p>
169 212
170<p> 213<p>
171As an example we will temporarily remove java from the USE-setting 214As an example we will temporarily remove java from the USE-setting
172during the installation of mozilla. 215during the installation of mozilla.
173</p> 216</p>
174 217
175<note>
176The <c>emerge</c> command will be discussed more thoroughly in <uri
177link="?part=2&amp;chap=2">Portage and Software</uri>.
178</note>
179
180<pre caption="Using USE as evironment variable"> 218<pre caption="Using USE as environment variable">
181# <i>USE="-java" emerge mozilla</i> 219# <i>USE="-java" emerge mozilla</i>
182</pre> 220</pre>
183 221
184</body> 222</body>
185</subsection> 223</subsection>
203</pre> 241</pre>
204 242
205</body> 243</body>
206</subsection> 244</subsection>
207<subsection> 245<subsection>
208<title>Precendence</title> 246<title>Precedence</title>
209<body> 247<body>
210 248
211<p> 249<p>
212Of 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
213USE 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
214<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
215by priority (first has lowest priority): 253by priority (first has lowest priority):
216</p> 254</p>
217 255
218<ol> 256<ol>
219 <li> 257 <li>
220 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
221 </li> 260 </li>
222 <li> 261 <li>
223 Inherited USE setting if a package from 262 Inherited USE setting if a package from
224 <path>/etc/make.profile/use.defaults</path> is installed 263 <path>/etc/make.profile/use.defaults</path> is installed
225 </li> 264 </li>
226 <li> 265 <li>
227 User-defined USE setting in <path>/etc/make.conf</path> 266 User-defined USE setting in <path>/etc/make.conf</path>
267 </li>
268 <li>
269 User-defined USE setting in <path>/etc/portage/package.use</path>
228 </li> 270 </li>
229 <li> 271 <li>
230 User-defined USE setting as environment variable 272 User-defined USE setting as environment variable
231 </li> 273 </li>
232</ol> 274</ol>
241# <i>emerge info</i> 283# <i>emerge info</i>
242</pre> 284</pre>
243 285
244</body> 286</body>
245</subsection> 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:
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>
332
333</body>
334</subsection>
246</section> 335</section>
247<section> 336<section>
248<title>Package specific USE-flags</title> 337<title>Package specific USE-flags</title>
249<subsection> 338<subsection>
250<title>Viewing available USE-flags</title> 339<title>Viewing available USE-flags</title>
251<body> 340<body>
252 341
253<p> 342<p>
254In the next chapter on <uri link="?part=2&amp;chap=2">Portage and Software</uri>
255we will explain how to manage your installed software and how to work with
256<c>emerge</c>. However, we will give you a primer on <c>emerge</c> by showing
257you how to view what USE-flags a package uses.
258</p>
259
260<p>
261Let 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
262find 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>
263anything) and <c>--verbose</c> (give more output) options: 345options:
264</p> 346</p>
265 347
266<pre caption="Viewing the used USE-flags"> 348<pre caption="Viewing the used USE-flags">
267# <i>emerge --pretend --verbose mozilla</i> 349# <i>emerge --pretend --verbose mozilla</i>
268These are the packages that I would merge, in order: 350These are the packages that I would merge, in order:
278dedicated to package information called <c>etcat</c> which resides in the 360dedicated to package information called <c>etcat</c> which resides in the
279<c>gentoolkit</c> package. First, install <c>gentoolkit</c>: 361<c>gentoolkit</c> package. First, install <c>gentoolkit</c>:
280</p> 362</p>
281 363
282<pre caption="Installing gentoolkit"> 364<pre caption="Installing gentoolkit">
283# <i>emerge --usepkg gentoolkit</i> 365# <i>emerge gentoolkit</i>
284</pre> 366</pre>
285 367
286<p> 368<p>
287Now 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
288certain package. For instance, for the <c>gnumeric</c> package: 370certain package. For instance, for the <c>gnumeric</c> package:

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